The Multi-Purpose Detector (MPD) is one of the three experiments of the Nuclotron Ion Collider-fAcility (NICA) complex,
which is currently under construction at the Joint Institute for Nuclear Research in Dubna. With collisions of heavy ions
in the collider and fixed target modes, the MPD will cover the energy range of 2.5-11 GeV to scan the high baryon-density region
of the QCD phase diagram. With an expected statistics of 50-100 million events collected during the first run, the MPD will be able
to study a number of observables, including measurements of light hadrons and hypernuclei production, particle flow, correlations
and fluctuations. In this report, we will review the status of the MPD experiment and its physics program,
with a focus on the first expected measurements to be performed.

The main goal of the NICA physics program is to study the QCD phase diagram in the poorly explored region of high net-baryon density. The BM@N experiment at NICA is well-suited for measuring a variety of hadron species in high-multiplicity nucleus-nucleus collisions. To bridge the gap between measurements at low energies at SIS-18 and higher energies at AGS, BM@N has performed an energy and system-size scan using Ar and Xe projectiles at beam kinetic energies ranging from 1.6 to 3.8 GeV per nucleon. The study of hadron and light nuclei production in intermediate-mass systems plays a crucial role in revealing the reaction dynamics and the nuclear matter Equation of State (EoS) at densities 2–4 times higher than normal nuclear density.

This report first overviews the current status and recent upgrades of the BM@N setup. The main part discusses recent results on charged pion, kaon, proton, and light nuclei production in centrality-selected Ar+A (A=C, Al, Cu, Sc, Pb) and Xe+CsI collisions. Particle spectra, yields, and ratios are presented and compared with transport model predictions incorporating different EoS implementations.

The Spin Physics Detector (SPD) is a universal detector at the NICA collider under comissioning at JINR, Dubna. The SPD is intended to study the spin structure of the proton and deuteron and other spin-related phenomena using a unique possibility to operate with polarized proton and deuteron beams at a collision energy up to 27 GeV and a luminosity up to $10^{32}$ cm$^{-2}$ s$^{-1}$. As the primary goal, the experiment aims to provide access to the gluon TMD PDFs in the proton and deuteron, as well as the gluon transversity distribution and tensor PDFs in the deuteron, via the measurements of specific single and double spin asymmetries using different complementary probes such as charmonia, open charm, and prompt photon production processes. Other polarized and unpolarized physics is possible, especially at the first stage of NICA operation with reduced luminosity and collision energy of the proton and ion beams. The physics program of the SPD and the design of the SPD setup will be presented.

Quark-gluon plasma created in heavy-ion collision experiments is subjected to rapid rotation which might modify QCD properties. In this report we are going to review the results of lattice study on how rapid rotation influences QCD properties. In particular, the following results will be considered: equation of state of rotating gluodynamics, spatial confinement/deconfinement transition resulting from rotation and properties of QCD at finite spin density.

TBA

The main directions of searching for New Physics in fixed-target
experiments with the proton beam energy up to 1000 GeV are
discussed.

Development of the low-energy nuclear physics in Russia is discussed with special emphasis on the project of the Universal Compton Radiation Source (UCRS).

The construction of the UCRS accelerator complex was proposed as one of the first large-scale scientific project of the Russian National Center of Physics and Mathematics (Sarov) [1]. The construction started in the beginning of 2026 and the commissioning is planned for 2031. The complex consists of two electron accelerators with maximum energies $E_e = 120$ MeV (120 MeV LINAC) and $E_e = 2.0$ GeV (200 MeV LINAC + booster synchrotron) and two storage rings operational in the energy ranges $E_e \sim 70-120$ MeV and $E_e \sim 0.5-2.0$ GeV. The (quasi)monochromatic gamma and X-ray quanta are generated by the inverse Compton scattering of laser photons with $E_{ph} \sim 0.1-3.3$ eV by relativistic electrons. Energy of generated photons $E_{\gamma}$ continuously covers the range from 10 keV to 1.5 GeV providing a broad scientific universalism of the complex.

The main research objectives of the complex are the fundamental problems of nuclear photonics in the energy range $E_{\gamma} \sim 0.5-60$ MeV [2]: photonuclear reactions, photofission, nuclear spectroscopy, high-precision study of the regions of giant dipole resonance and pygmy dipole resonance, reactions relevant to nuclear astrophysics, etc. X-ray radiation with $E_{\gamma} \sim 10-700$ keV is planned to be used for materials science, non-destructive testing and biology. The availability of high-energy gammas with $E_{\gamma} \sim 60-1500$ MeV opens scientific opportunities in the field of hadron photonics and high-energy nuclear physics (Compton scattering on nucleons and nuclear matter, meson degrees of freedom in nuclear matter, etc.). Electron bunches with a maximum energy up to $E_{e} \sim 2$ GeV can be used for generation of intense ultrashort pulses of gamma radiation for studies of fast processes, and in combination with the planned terawatt laser for research in the field of high-energy density physics (e.g. nonlinear electrodynamics, etc.).

[1] https://ncphm.ru/science/infrastructure/megascience/iki

[2] L.V. Grigorenko et al., Scientific program of INOK – Compton source of the monochromatic gamma-quanta at NCPhM, FIZMAT 3-4 (2023) 121-259 (in Russian) [https://fizmat-journal.ru/issues/2023/3].

TBA

Dark matter constitutes one of the most compelling open questions in modern physics. One of the most compelling and theoretically-motivated candidates is the Weakly Interacting Massive Particle (WIMP), a hypothetical particle beyond the Standard Model with a mass typically ranging from a few GeV to several TeV. Direct WIMP searches are being actively pursued through a variety of experimental approaches, the most promising of which employ noble-element targets, such as argon and xenon. While xenon-based experiments presently set the most stringent exclusion limits over a broad WIMP mass range, future argon detectors are expected to achieve comparable sensitivity while offering enhanced potential for WIMPs with masses of a few GeV, commonly referred to as “low-mass WIMPs”. Interest in this mass region has grown significantly in recent years as increasingly stringent constraints have challenged conventional WIMP scenarios.
This contribution presents an overview of past, current and future argon-based direct-detection experiments using both single-phase and dual-phase technologies. The main features and results of previous-generation detectors, such as DarkSide-50, are reviewed, followed by a discussion of ongoing efforts, including DEAP-3600 at SNOLAB (Canada) and DarkSide-20k at LNGS (Italy). Particular emphasis is placed on DarkSide-20k, which combines a multi-ton liquid-argon target with underground argon depleted in 39Ar and a novel photodetection system based on cryogenic silicon photomultipliers (SiPMs). Finally, the prospects for the next-generation Argo experiment are presented.

Inflation is conventionally described in terms of fundamental scalar fields whose microscopic origin remains unknown. We propose [1,2] a fundamentally different mechanism in which inflation emerges from fermion condensates generated by torsion-induced four-fermion interactions in Einstein–Cartan–Holst gravity. Starting from a purely fermionic theory, we derive a two-condensate effective description whose inflationary dynamics resembles hybrid inflation but exhibits a qualitatively new exit mechanism.
The central result is the emergence of a density-driven waterfall transition. During inflation, axial charge production continuously increases the fermion density and the associated chiral chemical potential. Solving the finite-density gap equation, we show that above a critical axial density the condensate no longer admits a symmetry-broken solution. Inflation therefore terminates through the evaporation of the condensate itself rather than through the inflaton crossing a critical field value. This mechanism naturally triggers rapid energy transfer to fermionic degrees of freedom and provides a microscopic realization of instant preheating.
The post-transition condensate is unstable to fragmentation into charged non-topological solitons. These objects can subsequently collapse into primordial black holes, generating a calculable relic population whose properties are determined by the same condensate dynamics that drives inflation [3]. Because the underlying theory is intrinsically chiral and connected to dynamical Chern–Simons gravity, the scenario simultaneously predicts parity-violating signatures [4].
The framework unifies inflation, reheating, soliton formation, primordial-black-hole production, and parity-violating phenomenology within a single gravitationally induced fermion-condensation mechanism. It provides a composite alternative to scalar-field inflation and identifies correlated observational signatures that can test the role of spacetime torsion in the early Universe.

References
[1] S. Alexander, P. Chen, J. Liu, A. Marciano, M. Sasaki and X. L. Su, Hybrid inflation from fermion condensation, Phys. Lett. B 873 (2026), 140193 doi:10.1016/j.physletb.2026.140193 arXiv:2509.25290 [gr-qc]]
[2] S. Alexander, P. Chen, J. Liu, A. Marciano, M. Sasaki and X. L. Su, Fermion Condensate Inflation, Dynamical Waterfall Mechanism and Primordial Black Holes, arXiv:2604.21535 [hep-th].
[[3] E. Cotner, A. Kusenko, M. Sasaki and V. Takhistov, Analytic Description of Primordial Black Hole Formation from Scalar Field Fragmentation, JCAP 10 (2019), 077 doi:10.1088/1475-7516/2019/10/077 arXiv:1907.10613 [astro-ph.CO].
[4] J. Liu, S. Alexander and A. Marciano, Birefringence in fermion-attenuated gravitational wave power spectrum, Phys. Lett. B 866 (2025), 139499 doi:10.1016/j.physletb.2025.139499 arXiv:2501.08240 [gr-qc].

The "Nadya" compact precision spectrometer, currently under development at MEPhI (National Research Nuclear University), is designed to detect and identify directional charged-particle fluxes in the energy range from several tens to several hundred MeV. This energy range is of interest for the search for and detailed study of heliogeophysical phenomena, Earth's magnetospheric physics, radiation belt dynamics, and the spatiotemporal variations of the low-energy component of galactic cosmic rays (GCRs) in high-latitude regions. The experiment's scientific program focuses particularly on the continuous monitoring of solar cosmic rays (SCRs) and the investigation of the mechanisms governing their generation, acceleration, and propagation in the interplanetary medium during periods of heightened solar activity. The data obtained will be vital for real-time space weather monitoring, modeling the radiation environment in near-Earth space, and assessing radiation loads on spacecraft onboard electronics; these data will complement findings from previous experiments—including precision missions like PAMELA, for which this specific energy range was inaccessible. The "Nadya" instrument is scheduled for launch aboard the A-100 unified spacecraft platform (developed by the company L5) into a circular sun-synchronous orbit with a mean altitude of 450–650 km and an inclination of approximately 98°. This orbital configuration ensures regular passes over polar regions characterized by low geomagnetic cutoff thresholds, as well as through the South Atlantic Anomaly—conditions essential for a comprehensive analysis of particle flux anisotropy across various helio-geophysical environments. The spacecraft launch is planned for the first half of 2027. The key performance characteristics of the scientific instrumentation have been optimized to meet the strict resource constraints of small satellite platforms: the total instrument mass is approximately 3 kg, and the average power consumption during standard measurement operations does not exceed 15 W. The projected volume of scientific telemetry data transmitted to the ground control segment reaches 10 GB per day, ensuring high statistical significance for the recorded events.

The Monte Carlo event generators HYDJET and HYDJET++ are widely used to simulate high-energy heavy-ion collisions. This study compares their predictions with LHC measurements in Pb-Pb collisions at the LHC Run 3 energy 5.36 TeV in c.m.s. per nuclear pair. Charged-particle pseudorapidity spectra and multiplicity as a function of collision centrality are investigated. It is found that both HYDJET++ with its default tune and HYDJET with the special tune reproduce the experimental data well at LHC energies.

The first results of numerical simulations of the neutron star merger process using the smoothed particle hydrodynamics (SPH) method are presented. To generate the initial equilibrium configuration of the binary system that accounts for the tidal deformation of the components, a new method has been applied: halted-pendulum relaxation. The method has been implemented in the well-known astrophysical code PHANTOM. In particular, values of the quadrupole moments of the stars at various separations from each other have been obtained as a result of the simulations. They enable the calculation of the gravitational-wave signal generated by the system and the determination of its deviation from the classical point-mass case described by Einstein's quadrupole formula.

In this work, the most accurate model for calculating the cumulative antineutrino and beta particle spectra of uranium and plutonium isotope fission products was developed and verified by comparison with experimentally obtained spectra of 92Rb, 142Cs, 90Sr, 90Y and 40K. The developed model shows best agreement with neutrino reactor experiments, such as RENO and Daya Bay, among all existing summation models. Additionally, the obtained model shows absence of reactor antineutino anomaly within the margin of error. Based on this model, the expected cumulative antineutrino spectra from uranium and plutonium fission in thermal and fast neutron reactors were obtained.

In this paper we revisit Primordial Black Holes (PBHs) clusters as Dark Matter (DM) candidates. Here we present continuation of our previous work, extending the analysis. The analysis is devoted to re-consideration of constraint on PBH abundance from stellar cluster observation in dwarf galaxy Eridanus II. We take into account non-trivial density profile of PBH clusters in order to re-estimate the energy exchange between PBHs and stars. Here we keep momentum approximation to strengthen the constraint making it robust. The impact of density profile concludes in the form of Coulomb logarithm, making analysis trivial, but showing important result. It is shown that density profile matters and energy exchange can be suppressed due to it considerably, making clusters of PBHs viable
DM candidates, if their core radius is sufficiently large.

We study neutrino spin and spin-flavor oscillations in spatially inhomogeneous multipolar magnetic fields of realistic astrophysical objects. Starting from the general neutrino electromagnetic interaction Hamiltonian, we derive the effective interaction Hamiltonian for an arbitrarily moving neutrino in a multipolar magnetic field expressed in spherical coordinates. An exact analytic expression for the geometric phase arising from the spatial inhomogeneity of the magnetic field is obtained. For the particular cases of neutrino propagation inside the astrophysical object along radial direction, the resonance conditions and adiabaticity parameters for spin-flip transitions are analyzed in core-collapse supernovae, using realistic magnetic field models and matter density profiles.

In this project, we consider the Einstein-Maxwell gravity to describe the color superconductivity in the odd dimensional SU(N_c) arbitrary gauge theory in the boundary (even dimensional bulk). We study the equation of motion of the color superconductivity in different dimension bulk and the number of color.

Comparison of energy spectra of electrons and antineutrinos can help in understanding the mechanism of beta decay, which is not fully clear yet. Measuring an antineutrino spectrum from a known beta isotope requires an experiment with a large, high-resolution detector and a powerful source. Mirror symmetry can be checked by measuring the antineutrino spectrum and comparing it to the beta one. Modern detectors of large volume allow to make this with a powerful enough source. The main challenge is obtaining a pure, powerful source. We propose to measure the antineutrino spectrum using a high-activity radioactive source of 90Sr-90Y (~1 MCi), located on the top of large volume detector, for example the current JUNO experiment.

A general understanding has emerged regarding the processes governing a wide range of nuclear reactions, particularly fission—see, for example, the review in [1]. Based on this understanding, computer codes have been developed to calculate total and partial cross-sections for the interaction of nuclei with light nuclear particles, specifically neutrons. All such codes rely on models describing various stages of the reaction, and each model involves specific parameters. Typically, however, only some of these parameters can be fixed, while the values of others remain uncertain.
In this work, we calculate the fission cross-section of the 237-Np nucleus as a function of incident neutron energy in the 0.1–30 MeV range and compare the results with experimental data [2–4]. This reaction was selected because recent work [5] provided additional information on the process—specifically, measurements of fission fragment angular anisotropy in the 0.4–200 MeV range. Reference [5] also presented a novel method for calculating angular anisotropy and demonstrated that a joint comparison of calculated and measured values for both the fission cross-section and angular anisotropy will allow obtaining additional information about the fission process. However, the authors of [5] were unable to reproduce the observed dependence of the fission cross-section on incident neutron energy in certain energy intervals.
In the present work, the open-source code TALYS (version 2.2) [6] was used to model the 237-Np(n,f) reaction for incident neutron energies ranging from 0.1 to 30 MeV. The complexity of modeling fission arises from the fact that, in addition to the optical model and level-density model parameters built into the code, we must also consider parameters defining the shapes of fission barriers and nuclear characteristics at those barriers. Typically, calculations performed in TALYS using default parameters fail to accurately reproduce the energy dependence of the fission cross-section. This case turned out to be exactly like this. Therefore, in this work, the parameters that determine both the shape of the double-humped fission barriers of Np isotopes with mass numbers from 238 to 235, as well as the collective increase in the level density and the shape of the nuclei on the humps of the barriers of these same isotopes, were varied. This approach enabled us to reproduce the experimentally observed energy dependence of the fission cross-section with high accuracy. The resulting parameter values can be incorporated into models describing the angular anisotropy of fission fragments in the ²³⁷Np(n,f) reaction, thereby yielding new insights into the characteristics of transition states at the fission barriers.

1. Capote R. et al. Nuclear Data Sheets, v. 110, p. 3107 (2009).
2. Shcherbakov O.A. et al. JNST, v. 39, suppl. 2, p. 230 (2002).
3. Paradela C. et al. PRC, v. 82, 034601 (2010).
4. Vorobyev A.S. et al. Bull. Russ. Acad. Sci.: Phys., v. 89, p. 1329 (2025).
5. Vorobyev A.S. et al. JETP Letters, v. 110, p. 242 (2019).
6. Koning A.J., Hilaire S., Goriely S. EPJA, v. 59, p. 131 (2023).

Development of compact pocket-style electron accelerators meeting safety regulations is a complementary task requiring stable, reliable, and reproducible particle sources with controllable parameters. We employed a new approach for pyroelectric accelerator operation - periodically varying temperature of lithium tantalate (LiTaO3) crystal. It enables to generate stable quasi-continuous electron beam with energy about few tens of keV. We managed to observe and characterize the avalanche process at pyroelectric effect in surrounding vacuum conditions. This phenomenon is responsible for multiplication of electrons between pyroelectric crystal and metallic target. We have demonstrated the great potential of this compact electron source by performing reliable energy-dispersive spectroscopy for element analysis of solid samples.

The research was supported by a grant from the Russian Science Foundation (Project No. 26-72-10002).

The processes of paired charmonium and bottomonium production in Z-boson decays are investigated within the relativistic quark model. Various decay mechanisms
are examined, and relativistic decay amplitudes are constructed, taking into account
the relative momenta of heavy quarks. Decay widths are calculated for various mechanisms in the nonrelativistic approximation and taking into account relativistic corrections.

To measure cumulative beta-particle spectra of uranium and plutonium fission products, the BETA experimental facility is located at the output of the 11th neutron beam of the research reactor at the National Research Center Kurchatov Institute. The experiment simultaneously measures beta-particle spectra from uranium and plutonium targets, as well as the background spectrum, in the same neutron flux. As part of the upgrade of the BETA facility, a scintillation beta spectrometer has been developed and the first measurements with radioactive sources are presented.

We study the scattering of twisted neutrons with orbital angular momentum (OAM) from nuclear targets. A theoretical model is developed for Laguerre-Gaussian neutron states, accounting for nuclear and electromagnetic interactions and their interference.

We show that OAM and beam localization significantly modify the differential scattering cross section, while spatially inhomogeneous polarization produces characteristic azimuthal modulations. The interference between nuclear and electromagnetic amplitudes is sensitive to the phase of the nuclear scattering amplitude, making angular asymmetries a potential tool for its experimental investigation. Our results demonstrate new possibilities for controlling and probing low-energy neutron-nucleus interactions using structured neutron beams.

Using perturbation theory for the fine-structure constant α and the electron-to-
muon mass ratio, we calculate new contributions to the hyperfine structure of the
ground state of the muon-electron helium atom. Compared to our previous results,
we incorporated new corrections in the second order of perturbation theory. This
calculation reduces the discrepancy between the theoretical value and the new ex-
perimental hyperfine structure measurement.

B-meson decays with ψ(2S) in the final state offer a way to study exotic hadrons with hidden charm alongside studies with J/ψ. This contribution reviews results from Belle, BaBar, CMS, and LHCb, from the first observation of the charged Z(4430) structure to recent amplitude analyses. The focus is on recent LHCb studies of B⁺ → ψ(2S)K⁺π⁺π⁻ and B⁺ → ψ(2S)K⁰ₛπ⁺ decays, which reveal new exotic structures and provide further information on the properties of Z(4430)⁺.

We discuss the signal readout system for cryogenic CsI(pure) scintillation detector of tritium neutrino. This detector is constructed in the frame of SATURN experiment for search of electromagnetic properties of neutrino in tritium decay. The elastic scattering of these neutrino at electrons in CsI scintillator deposits the energy below 1 keV that requires detection of extremely low signals. For this purpose, the CsI detector with SiPM light readout is placed in cryostat with liquid nitrogen temperature. The signals after photodetectors are additionally amplified for about three orders and arrange the event trigger. The wave-forms of the signals are digitized in fast analog-to-digital convertor. This work presents the current state of a detector readout system.

Measurements of collective flow provide access to the equation of state (EOS) of dense baryonic matter and offer insights into the initial collision geometry. Strange particles, produced during the hadronic phase, serve as probes of the strangeness enhancement mechanism in heavy-ion collisions. The $\phi$ vector meson resonance therefore plays a key role in future studies; however, reliable measurements of its directed ($v_1$) and elliptic ($v_2$) flow require large event statistics. In this work, we explore the feasibility of performing such measurements at the MPD experiment at 9.2 GeV by enhancing the dataset with simulated artificial $\phi$-meson production to achieve sufficient statistical precision.

This study investigates the stability of background conditions in the νGeN experiment at the Kalinin Nuclear Power Plant. It is demonstrated that fluctuations of the background count rate of the germanium detector inside the passive shielding are correlated with the intensity of photoabsorption peaks from radon-related gamma rays. Using data from periods with different intensity of these peaks, an energy spectrum of radon-related contribution to the experiment's region of interest is obtained.

We present a theoretical proposal for measuring correlation functions in a quantum field system based on the use of quantum quenches. Using the examples of massive and massless scalar field theories, we show that a short-term perturbation of the system leads to a dependence of the further evolution of the average field on the initial state’s correlation functions. Considering two types of perturbations,namely local and nonlocal quenches, we show which correlation functions can be measured in each of these cases. The proposed procedure can be applied to study non-Gaussian correlations.

This work addresses the combined use of photomultiplier tubes (PMTs) and polymethyl methacrylate (PMMA) wavelength‑shifting (WLS) plates within optical modules of the Hyper‑Kamiokande outer detector. The goal is to identify the PMT parameters that critically affect the module’s light yield and the veto efficiency. A comparative analysis of several PMT types with different photocathode characteristics and dark‑noise levels is performed. Special attention is paid to the local cathode sensitivity at the optical contact area with the WLS plate, as this factor governs the conversion efficiency of the shifted light.

The Spin Physics Detector (SPD) experiment is designed for studying a nucleon spin structure and other spin-related phenomena with polarized proton and deuteron beams. A Beam–Beam Counter (BBC) detector will be employed for a local polarimetry and luminosity measurements. High radiation conditions may cause the degradation of material properties and therefore a detector efficiency. To assess the potential damage, we studied ageing of key polymers used for BBC components: connectors and optical cement coupled to scintillator surface. The study of mechanical strength and transparency change for corresponding polymers has been performed.

The LHC collider is the only machine to study physics of bottom baryons. Among a majority of decays observed, the hidden-charm pentaquark observation is one of the most important output by the LHCb Collaboration. In the $\Lambda_b$- and $\Xi_b$-baryon decays both unflavor and strange pentaquarks accompanied by a light pseudoscalar meson were found. Doubly-strange pentaquarks are still waiting for their discovery in a similar channel or with a vector meson instead. The later ones seem to be more interesting for experimental Doubly-strange pentaquark observation by the LHCb Collaboration. The flavor $SU(3)$-symmetry can be used to relate widths of bottom-baryon weak decays into a pentaquark and light vector meson and predict their ratios as well as specify the most promising experimental channels.

The anisotropic flow of produced particles provides the insight into the transport properties and the equation of state (EoS) of strongly interacting matter. This talk presents directed flow ($v_1$) measurements of charged pions in Xe+Cs(I) collisions at 3.8A GeV, obtained with the BM@N experiment. Pion directed flow is studied as a function of centrality, rapidity, and transverse momentum. The results are compared with existing world data, and their implications for constraining the EoS of dense baryonic matter are discussed.

Precise measurements of β-spectra are highly relevant for a number of physical areas. For the investigations of the neutrino processes at nuclear reactors, such as the reaction of inverse beta-decay, elastic neutrino scattering on an electron or coherent scattering on nuclei, an accurate quantitative determination of the electron antineutrinos spectrum is required. These electron antineutrinos are emitted during beta-decays of fission fragments of uranium and plutonium isotopes, as well as during beta decays of various nuclei that arise as a result of neutron capture, so their spectrum can be reconstructed from the measured beta-spectra.
Our lab develops an experimental setup of beta-spectrometer based on silicon-lithium drift Si(Li) detectors designed to carry out the precise measurements of the beta spectra of various fissile isotopes of uranium and plutonium in the scheduled experiment at the PIK reactor after its launch. Individual Si(Li) detectors can be manufactured with a sensitive region thickness of up to 1 cm, which is sufficient to absorb electrons with an energy of up to 3.5 MeV. To register the electrons with higher energies the multilayer spectrometer consisting of several Si(Li) detectors is required.
However, usual Si(Li) detectors manufactured using standard technology have an unacceptably thick entrance window from the n-contact side. We propose an alternative method for n-contact creation allowing to produce the Si(Li) detectors with a thin entrance window from both n- and p-sides. An assembly of three such thin-window Si(Li) detectors will make it possible to register the full energy of 10 MeV beta-electrons. At the Conference the detailed description of the spectrometric properties of individual double-sided thin-window Si(Li) detectors and the results of entrance windows thickness measurements will be presented and discussed.
To suppress the accompanying gamma background a silicon transition detector with a thickness of 100–300 μm will be positioned in front of the first layer of Si(Li) detectors. Such configuration of the detectors effectively suppressed the background signals, but leads to a deterioration in the energy resolution of the spectra measured by the Si(Li) detector due to the passage of beta-electrons through the transition detector. The procedure of Si(Li) detector energy resolution restoration by the summation of pulse amplitudes of both detectors will also be discussed.

Modern analysis of data from early- and late-epoch cosmological probes has revealed statistically significant tensions between predictions for different stages of the Universe's evolution. Key among them are the discrepancies in the determination of the Hubble constant $H_{0}$ and the parameter $S_{8}$, which characterizes the amplitude of matter density fluctuations. One of the most promising ways to resolve these contradictions is the concept of dynamical dark energy, moderate observational indications of whose existence are contained in the recent DESI BAO DR2 data release. The gas of thin tubes of a massless scalar field also belongs to the class of dynamical dark energy models, since the parameter $w$ of its equation of state is a dynamical function of the density. In this work, we investigated the influence of the evolution of the gravitational field of a single closed thin tube of a massless scalar field, radially changing its size, on the trajectories of a test null string. We also investigated how constraints on the trajectories of test objects can macroscopically influence the dynamics of the accelerated expansion of the entire gas of thin tubes on cosmological scales.

Experiments searching for elastic scattering of non-relativistic dark matter (DM) particles off nuclei lose sensitivity at DM masses below 1 GeV, since light particles transfer to nuclei energy below the detection threshold. Scattering off electrons enables partial probing of the region of lighter particles. Relativistic particles can arise from the acceleration of DM by cosmic-ray particles, the neutrino background, supernova emission, and a number of other processes. Boosted dark matter (BDM) particles can produce a detectable signal in existing neutrino detectors or DM detectors upon interaction with electrons or nuclei.

The Borexino solar neutrino detector possesses an important advantage associated with a record-low background level when searching for BDM signals in the few-MeV range. In the current work, we analyze the energy spectrum data of the Borexino detector [1, 2] with the aim of searching for events from BDM particles accelerated by cosmic-ray electrons and the diffuse supernova neutrino background.

1. M. Agostini et al. (Borexino coll.), Phys. Rev. D 101, 062001 (2020)
2. D. Basilico et al. (Borexino coll.), Eur. Phys. J. C 86, 736 (2026)

\begin{document}

\title{Understanding of electromagnetic and gravitational form factors for nucleon and $\Delta$ with pion meson cloud}

\newcommand{\email}[1]{\thanks{\href{mailto:#1}{#1}}}

\author[a,b]{Jiaqi Wang\email{jqwang@ihep.ac.cn}}
\author[c]{Dongyan Fu\email{fudongyan@impcas.ac.cn}}
\author[a,b]{Yubing Dong\email{dongyb@ihep.ac.cn}}

\affil[a]{Institute of High Energy Physics, Chinese Academy of Sciences,
Beijing 100049, China}
\affil[b]{School of Physical Sciences, University of Chinese Academy
of Sciences, Beijing 101408, China}
\affil[c]{Southern Center for Nuclear-Science Theory (SCNT),
\authorcr
Institute of Modern Physics, Chinese Academy of Sciences, Huizhou 516000, China}

\maketitle

The electromagnetic and gravitational form factors of the nucleon and $\Delta(1232)$ resonance are studied
simultaneously using a covariant quark-diquark approach, and the pion cloud effect on the form factors is
explicitly discussed. The calculated electromagnetic form factors of nucleon are compared to the experimental
data in order to determine the parameters of our approach. Then, the gravitational form factors of the
nucleon and $Delta$-isobar are evaluated with the same parameters, and moreover, the transition form
factors of $N-\Delta$ are also estimated. The electromagnetic and mechanical properties, such as the
charge radii, magnetic moments, and mass radii are presented. Moreover, the D-term, which is believed to be
connected with the internal force inside the baryons, is also discussed. It is found that our results
are in reasonable agreement with the experiment and lattice results, and in particular, our results suggest
that the pion cloud contribution plays an indispensable role~\cite{Wang:2026nlr, Wang:2024abv},
especially for the magnetic moments and the D-term of the systems, and therefore the sign problem of the
positive D-term in our previous model calculations with quark-diquark approach is solved~\cite{Wang:2023bjp, Fu:2023ijy}.

\begin{thebibliography}{99}
\bibitem{Wang:2026nlr}
Wang, Jiaqi and Fu, Dongyan and Dong, Yubing,
"Form factors of $\Delta$(1232) and the electromagnetic $N-\Delta$ transition", arXiv: 2602.19480.

\bibitem{Wang:2024abv} Wang, Jiaqi and Fu, Dongyan and Dong, Yubing,
"A systematic study of nucleon form factors with the pion cloud effect", arXiv: 2410.14953; Eur. Phys. J. 85
1254 (2025).

\bibitem{Wang:2023bjp} Wang, JiaQi and Fu, Dongyan and Dong, Yubing, "Form factors of decuplet baryons in
a covariant quark{\textendash}diquark approach", arXiv: 2311.07149; Eur. Phys. J. C84, 79 (2024).

\bibitem{Fu:2023ijy} Fu, Dongyan and Wang, JiaQi and Dong, Yubing, "Form factors of {\ensuremath{\Omega}}-
in a covariant quark-diquark approach", arXiv: 2306.04869; Phys. Rev. D 108, 076023 (2023).

\end{thebibliography}
\end{document}

Searches for submicrosecond and nanosecond optical transients are motivated by studies of rapid astrophysical processes and the search for extraterrestrial intelligence (SETI). Imaging atmospheric Cherenkov telescopes can be used to search for such transients during regular observations. Coincident signals from multiple telescopes, combined with image analysis, help identify candidate events and suppress the extensive air shower background. In this work, the event selection criteria are described, and preliminary results from an analysis of TAIGA-IACT data from 2022–2025 are reported. Prospects for further development of the search method are also discussed.

In the dissociation of neutron-rich krypton, neutron emission accompanies the formation of charged fragments. Information on neutron multiplicity and angular distributions complements the analysis of α-particle correlations and helps characterize the composition and kinematics of the breakup products. Estimating the sensitivity of nuclear emulsion to this neutron component is therefore an important methodological step in the study of such fragmentation channels.

Secondary interaction vertices (stars) without an incoming charged-particle track provide an indirect probe of neutrons produced in the multiple dissociation of krypton nuclei at 950 MeV per nucleon in nuclear emulsion. We examine the topological criteria for identifying candidate neutron-induced stars within the fragmentation cone defined by relativistic hydrogen and helium fragments, and quantify the role of observation geometry using Geant4 simulations.

Neutron and proton transport at a kinetic energy of 950 MeV is simulated with the QBBC physics list in a homogeneous emulsion model. Two configurations are compared: transverse passage through a 4 mm layer and emission from a fragmentation vertex with an effective path length of 45 mm.

These estimates demonstrate the strong geometrical dependence of sensitivity to the neutron component. They provide a basis for interpreting the frequency of secondary stars statistically, with the efficiency of identifying stars without an incoming track requiring separate assessment.

The presented work discusses the features of the developed fully connected three-layer neural network for data analysis. The model was created to process .root data from the open CERN data library. The goal of this model is to identify the rare process of B+-meson production and its subsequent decay: B⁺ → J/ψ + K⁺, J/ψ → μ⁺ + μ⁻.

B⁺ mesons contain a b quark and are heavy, unstable particles. In a real experiment, most of the recorded data is “background”: random combinations of particles that, in terms of their kinematic characteristics, are similar to the decay being sought. The neural network acts here as a “smart” filter that discards anything that is not a decay. Several physical features are fed into it as input, and then the network calculates the probability that the event is a signal. Our neural network demonstrated high accuracy values (0.977) in filtering the signal from the background, thereby demonstrating the applicability of deep learning methods in collider data analysis.

Atmospheric muon spectra are used in a range of cosmic-ray studies, including investigations of extensive air showers, atmospheric particle production, and atmospheric neutrino fluxes, as well as for validating particle-transport and cascade models. In particular, the spectrum is critical for estimating matter distribution in muography. For practical applications, compact analytical parameterizations are preferable to computationally demanding Monte Carlo simulations, for example, when optimizing detector configurations or estimating exposure times. However, the accuracy of commonly used parameterizations at large zenith angles remains an important issue.
We tested four analytical parameterizations of the differential atmospheric muon energy spectrum - Tang, Shukla, Reyna, and Bogdanova - against an independent experimental database from nine experiments, covering zenith angles from 0° to 90°. None of the considered parameterizations with published parameters provides satisfactory agreement with the experimental data over the full zenith-angle range. By fitting each zenith interval we obtained the systematic angular dependence of the model parameters. This indicates that the existing functional forms do not completely capture the angular dependence of the muon spectrum.
These results motivate further development of functional forms or parameterizations with angle-dependent parameters, which could improve the accuracy of atmospheric muon flux for applications. Additional experimental measurements, especially at large zenith angles could also help improve the description of these dependences.

A method is proposed for the automatic tuning of the operating parameters of silicon photomultipliers (SiPMs) in the two-coordinate scintillation hodoscope of the SPASCHARM experiment using the atmospheric muon flux. The developed approach is intended to provide reproducible selection of discrimination thresholds and SiPM bias voltages, as well as to monitor the stability of detector performance during the experiment.

The hodoscope under study is used in the SPASCHARM experiment and consists of two mutually perpendicular planes, each containing 32 scintillation elements; light from each element is detected by an individual SiPM. Atmospheric muons are used as a natural source of penetrating charged particles, enabling the detector to be tuned directly in its operating geometry without the use of an external radioactive source.

The readout electronics produces a binary indication of whether a preset discrimination threshold has been exceeded. The SiPM response is therefore studied by sequentially scanning the threshold at different bias voltages. The measured dependence of the counting rate R(T) on threshold T represents an integral threshold characteristic. To analyze the amplitude structure of the signal, the differential characteristic -dR/dT is used; it is related to the pulse-amplitude distribution and makes it possible to identify the transition region from noise triggers to signals caused by traversing particles.

Event candidates are identified using spatially consistent hits in neighboring scintillators in both coordinate planes. The accidental-coincidence level is estimated by applying a time shift between one plane and the other. The operating point is selected using a combination of observables: the single-count rate, the coincidence rate of neighboring elements, the rate of muon-like events, and the estimated accidental background.

We present a detailed comparison of Bayesian criteria with three non-informative priors - flat, Jeffreys, and scale-invariant - for testing a signal against an unknown background and compare them with the classical frequentist Li-Ma approach in the On/Off problem. We perform Monte Carlo simulations for various background levels and evaluate the Li-Ma and Bayesian criteria by their Type I error rates. We then simulate a nonzero signal and compare the criteria in terms of Type II error rates. We find that both the Li-Ma criterion and the Bayesian criterion with the Jeffreys prior control Type I error well, excluding the case of small background b<0.5; the Bayesian criterion with the Jeffreys prior is statistically more powerful than the Li-Ma criterion for b≲40. (based on preprint 2609.11683 [astro-ph.IM])

Centrality determination is an essential step in the analysis of heavy-ion collisions and the comparison of experimental results with model calculations. At beam energies of a few GeV per nucleon, trigger selection and the primary-vertex reconstruction requirement preferentially suppress peripheral events. Accounting for these losses is necessary to define centrality classes relative to the total inelastic nucleus–nucleus cross section.
This work presents centrality determination results for Xe+CsI collisions at a beam energy of 3.8A GeV using data from the first BM@N physics run. The analysis employs charged-particle multiplicity and two approaches: the Monte Carlo Glauber method and a modified direct reconstruction method based on Bayes’ theorem. In the latter approach, the conditional multiplicity distribution at a fixed impact parameter is described by a gamma parametrization using fully reconstructed simulated events. The multiplicity dependence of the event registration and selection efficiency is reconstructed with both methods, while its impact-parameter dependence is also obtained with the direct reconstruction method.
The sensitivity of the results to nuclear geometry parameters, the inelastic nucleon–nucleon cross section, and the choice of transport model is investigated. The Monte Carlo Glauber method yields an integrated efficiency of 72.72%, with deviations of −1.55 and +0.86 percentage points corresponding to the envelope of the variations considered. The mean and standard deviation of the direct reconstruction results obtained using DCM-QGSM-SMM, UrQMD-AMC, JAM2 MD2, and SMASH are (72.8 ± 1.0)%. These estimates characterize the model-related uncertainty components investigated. The shape of the multiplicity-dependent efficiency is validated by comparing experimental distributions recorded with the CCT2 and BT triggers. The two methods yield consistent results, with the largest model dependence observed in the peripheral region.

Nuclear self-consistent mean field result in appearance of series of single-particle states [1, 2], which can be obtained within Folded Yukawa Potential [3, 4]. Combinatorial method is developed to calculate level density $\rho$. In this approach, it's possible to also get metastable states, leading to altering level density and effecting nuclear cross sections of, in particular, astrophysical purpose [6], which were calculated in TALYS software package [5] with the implementation of obtained level density.

1. Bohr A., Mottelson B. Nuclear Structure. Single-particle motion. — W. A. Benjamin,1969. — 1219 p.
2. Ring P., Shuck P. The Nuclear Many-Body Problem. — Springer-Varlag. 1980.
3. Uhrenholt H., Aberg S., Moller P. et. al. Combinatorial nuclear level-density model //
   Nuclear Physics A. 2013. V. 913. P. 127.
4. Nix J. R. Calculation of fission barriers for heavy and superheavy nuclei // Annual
   Review of Nuclear Science. 1972. V. 22(1). P. 65-120.
5. Koning A., Hilaire S., Goriely S. TALYS-1.9. A nuclear reaction program. User Manual.
   — 2017.
6. Murphy R. J., Kozlovsky B., Kiener J., Share G. H. Nuclear gamma-ray de-excitation lines and
   continuum from accelerated-particle interactions in solar flares // The American Astronomical
   Society. 2009. V. 183(1). P. 142.

For a system comprised of a large number of particles, it is extremely difficult to specify their interactions analytically. The multi-agent approach provides a possibility to construct a numerical model of a system composed of many particles. Such many-particle system stabilizes over time, and its final state is, to a certain degree, independent of the initial conditions. The multi-agent approach is actively used in modern computer science and control theory for control of distributed, decentralized networks.

This work employs an approach based on the Vicsek model [1], which was proved analytically by Morse [2] and subsequently found numerous applications including load balancing [3], opinion dynamics [4], swarm control [5]. Its application to nuclear system modelling was proposed in [6]. In these applications, the key feature is the agents' ability to coordinate without external influence. The capacity of such coordination has been recently demonstrated for AI agents [7].

The implemented algorithm makes it possible to simulate the aggregation and evolution of proton-neutron system as well as the clustering of nuclear many-particle subsystems, while accounting for long-range but relatively weak Coulomb-type interactions. At the heart of the algorithm lies a consensus mechanism that balances the influence of the mutual attraction and repulsion of particles and models the system's transition to a stabilized state. The multi-agent nature of the proposed model allows evading the problem of specifying a dynamical system that describes many-body interactions. It scales efficiently and allows simulating a many-particle system with a large number of particles.

1. T. Vicsek, A. Czirók, E. Ben-Jacob, I. Cohen, and O. Shochet (1995) Physical review letters, 75(6), 1226.
2. A. S. Morse, A. Jadbabaie, J. Lin (2003) IEEE Trans. Autom. Control, 48. p. 988.
3. E. Borisoglebskaya, V. Erofeeva, O. Granichin, Y. Ivanskiy, and N. Kizhaeva, (2023) Proc. 9th International Conference on Control, Decision and Information Technologies, pp. 2032-2036.
4. N. E. Friedkin, A. V. Proskurnikov, R. Tempo, and S. E. Parsegov (2016). Science, 354(6310),
   pp. 321-326.
5. R. Olfati-Saber (2006) IEEE Trans. Autom. Control, 51(3), pp. 401-420.
6. Y. Ivanskiy, A. Unzhakova (2022) Bull. Russ. Acad. Sci.: Phys. 86 (9), 1108-1110.
7. G. De Marzo, C. Castellano, and D. Garcia (2026) Science Advances, 12: eaea6091.

In this work, we focused on the conditions at the Cosmic Dawn, before cosmic reionisation. We place new constraints on the fraction of the neutral hydrogen of the intergalactic medium at z = 9.02-14.18, after analysing Lyman-alpha emission (including upper limits) from 94 galaxy sources. Of these sources, there were 91 3σ upper limits and 3 detections. This analysis was done using JWST data for both PRISM and grating measurements, and incorporated both spectrometric and photometric measurements. New spectra from sources such as JADES Goods-North are included, while one anomalous detection from JADES Goods-South was excluded since it exhibited an abnormally high equivalent width (EW). We updated the IGM neutral fraction (x_HI) to be 0.889 (+0.073 / -0.084). Furthermore, from our model, we found a significant distinction between xHI when variable ionised bubble size was considered versus a fixed bubble size.

We investigate the production of millicharged particles (mCPs) by the Schwinger mechanism in thunderstorms in the atmospheres of different planets in the Solar system. We consider a thundercloud as a giant capacitor that can be discharged in two ways: either by lightnings or by mCP production. Taking into account the observation of lightning strikes, we establish the constraints on the charge and mass of mCPs. We examine two types of cloud configurations: a simple arrangement of two clouds, and a more complex layered structure that gives rise to potential wells. In the latter case, we take into account the effects of Bose enhancement for scalar mCPs, and Pauli blocking for fermionic ones.
We use the observational data of planetary atmospheres obtained by satellite missions to establish constraints on the charge and mass of mCP particles. The best constraints came from the observation of thunderstorms in Saturn's atmosphere under an assumption of layered cloud structure: we obtain a lower limit on the charge of $10^{-24}$ for bosonic mCPs. These constraints for bosons are, to the best of our knowledge, the best in the literature.

Modern nuclear databases such as NuDat 3 and ENSDF provide extensive experimental
information on level energies, spins, parities, and decay modes. However, these databases
lack tools for automated comparison with theoretical predictions and do not provide
complete single-particle level schemes, particularly for exotic nuclei far from stability.
In this work, we present a systematic study of nuclear level structures for isotopes
with Z = 10–72 using the realistic Woods–Saxon potential. The potential parameters are
determined using the Bohr–Mottelson systematics. The radial Schrödinger equation is
solved numerically using the high-accuracy Numerov method.
A software module for NATI (Nuclide Analysis and Technical Interface) has been developed. The module automatically constructs single-particle level filling schemes and
exports results in JSON, CSV, and SVG formats. It includes automated comparison with
experimental data from ENSDF.
The methodology has been validated for three reference nuclei: 40Ca (Z = 20, N = 20),
56Fe (Z = 26, N = 30), and 116Sn (Z = 50, N = 66). The calculated magic gaps of
6.4 MeV, 7.6 MeV, and 7.9 MeV are in good agreement with experiment. The average
deviation between theoretical and experimental single-particle energies is 0.4–0.7 MeV.
The developed tool provides a data-ready approach for nuclear structure analysis and
can be applied for predictive filling of gaps in experimental data, particularly for exotic
nuclei with only 1–5 known levels.
Keywords: Woods–Saxon potential, nuclear shell model, ENSDF, Numerov method,
nuclear level schemes

Cosmic rays are fluxes of charged particles coming from interstellar space. When primary cosmic-ray particles enter the Earth’s atmosphere, they interact with its nuclei and produce secondary particles, including muons. Due to their high penetrating ability, muons can reach the Earth’s surface and even propagate to large depths underground. The energy spectrum of muons changes significantly after they pass through a large amount of matter. There are different methods for calculating the energy spectrum of underground muons, for example, Monte Carlo simulations. This method can provide high accuracy, but it requires large computational resources. In this work, an analytical method for estimating the muon energy spectrum at large depths is considered for different values of parameters related to electron-positron pair production, bremsstrahlung, photonuclear interactions, and ionization energy losses. The analytical muon energy spectrum was studied at different depths, and the influence of these parameters on the spectrum was estimated. Special attention was paid to the high-energy region, with muon energies of the order of TeV.

The BBC is a component of the SPD detector at the NICA collider. In the context of a multichannel architecture comprising up to 256 silicon photomultipliers with readout electronics based on the FERS‑5200 system, continuous real‑time monitoring of the detector status becomes essential.

This work proposes the DAQ system implemented on a microservice architecture, which overcomes the limitations of the CAEN open-source control and readout software Janus. This system includes a modified process (JanusC) that outputs data to a stream, a converter to a packet‑based data format (raw2b), an event‑merging process (ems), a file‑writing process (writer), as well as a converter to the ROOT representation (b2r) and a configurable histogrammer (r2h). The DAQ system is controlled by the supervisor process with GUI written on the Python language using the Makefile, which describes the system’s processes interaction. The system's operation has been verified using cosmic muons with four sectors of the BBC prototype, as well as on the Nuclotron beam with two sectors. The developed solution is suitable for operation at the BBC prototyping stage and can be adapted for other scintillation detectors (f.e. ZDC) with channel‑by‑channel signal readout.

TAIGA-100 is a project of a large-scale astrophysical complex designed to solve a wide range of fundamental problems in gamma astronomy in the energy range from 300 GeV to above 1 PeV, cosmic ray (CR) physics from 100 TeV to 10 EeV, particle astrophysics, neutrino physics, and interdisciplinary research. The complex will include several types of detectors for registering different components of extensive air showers (EAS) over an area of 100 km^2. The basic elements of the project will be wide-angle atmospheric Cherenkov stations with a field of view of ~2 sr and water Cherenkov detectors (WCD) with an area of ~40 m^2, supplemented by scintillation counters and radio antennas. Atmospheric Cherenkov telescopes are also planned to be placed in the central part of the new installation, and fluorescence detectors on its periphery.

The construction of the TAIGA-100 complex is planned to be carried out in stages. At present, work is proceeding in three key directions. First, computer simulations are being performed to determine the optimal configuration of the installation and its potential, as well as to develop methods for reconstructing EAS parameters and primary radiation. Second, a site is being sought for the TAIGA-100 complex. Third, detector systems are being developed. Within the latter direction, the construction of a pilot installation with an area of 0.5 km^2 is also planned, using the infrastructure and operational experience of the existing TAIGA-1 gamma observatory. As a first step, in autumn 2025 an experimental station based on a WCD prototype with an area of ~7 m^2 was created and put into data taking. At the next stage, two full-scale water detectors are expected to be deployed during autumn 2026. In addition, the development and implementation of an innovative system for the extraction and transmission of trigger signals is planned.

The report presents a description and results of test measurements of the analog signal readout channel for the WCD over a wide dynamic range, the data acquisition system, and the system for generating and transmitting trigger signals.

We describe the experimental setup and data analysis procedure developed for measuring polarization correlations of 511 keV annihilation photons after Compton scattering at angles from 60° to 120°. The setup consists of two arms of Compton polarimeters with intermediate pre-scatterers placed in front of the main scatterers. Each arm is equipped with a ring of 16 scintillation counters covering the full azimuthal range. The upgrade of the setup for large-angle measurements and the corresponding changes in the data acquisition are discussed. The data processing pipeline includes energy calibration of all detectors with temperature drift correction, time-based selection of coincidence events, identification of pre-scattering interactions in the intermediate scatterer, and reconstruction of the scattering angle from the measured energy deposit. The classification of events into bins by scattering angle and the extraction of the visibility parameter from azimuthal angular distributions are described in detail. The entire procedure is validated against Monte Carlo simulations performed with the Geant4 toolkit. The resulting data set provides the input for the physics analysis of entanglement evolution during Compton scattering.

We present a prototype of a modular reactor antineutrino detector based on the inverse beta decay (IBD) reaction ($\bar\nu_e + p \rightarrow n + e^+$). Each module operates as an independent spectrometer based on a solid plastic scintillator block measuring $(700 \times 50 \times 50) \text{ mm}^3$, optically coupled to two vacuum photomultiplier tubes (PMTs) with an effective photocathode diameter of 46.5 mm. Neutron detection is planned to be performed using a $\text{ZnS(Ag)}+\text{B}_2\text{O}_3$ scintillating composite, optical fiber, and SiPMs. This work presents the design of the individual module and a $3 \times 3$ module array assembly, the corresponding experimental charge spectra, Monte Carlo simulation results, and the spectrometric performance of the detector based on this design.

In heavy-ion collisions at a beam energy of 3.8A GeV, a dense baryonic medium is formed in the nuclear overlap zone. The anisotropic flow of produced particles provides insight into the transport properties and equation of state (EoS) of this strongly interacting matter. This contribution reports preliminary results on the directed flow ($v_{1}$) of protons in Xe+Cs(I) collisions at 3.8A GeV, obtained with the BM@N experiment. The directed flow is studied as a function of centrality, rapidity, and transverse momentum. The results are compared with available world data and their role in constraining the EoS of dense baryonic matter is discussed.

Type IIP supernovae provide an opportunity for independent estimation of cosmological distances, making them a valuable tool for constraining the Hubble constant and testing cosmological models.
One of the methods for determining distances to Type II supernovae is the Expanding Photosphere Method (EPM), which does not require calibration via the cosmic distance ladder.
The EPM is based on the geometric relationship between the angular size of the supernova photosphere and its radius. The angular size of the photosphere is estimated from photometric observations in different photometric bands, while its radius can be determined from the photospheric expansion velocity measured from spectral lines. These quantities can then be used to estimate the distance to the supernova.

This work presents a practical algorithm for applying the EPM and the Standardized Candle Method (SCM) to photometric and spectroscopic observational data obtained with a telescope at the Caucasus Mountain Observatory of the Sternberg Astronomical Institute, Lomonosov Moscow State University.
For supernova SN 2024ws, distances obtained using the two methods are estimated and comparatively analyzed.
The validity of the physical assumptions underlying the EPM and SCM is investigated using numerical modeling type IIP supernovae.

Neutrinos emitted during the gravitational core collapse supernova are the most direct probe of processes in the stellar interior which are inaccessible to electromagnetic observations. Interpretation of signals from future flares by, e.g., JUNO, DUNE, IceCube-Gen2, KM3NeT, Baikal-GVD detectors, requires consideration of a complex set of physical effects [1] including generation of ultra-strong magnetic inductions, nonlinear evolution of neutrino fluxes etc. In this work we analyse neutrinos bursts emitted by a protoneutron star at supernova explosion taking into account effects of magnetization and oscillations. The neutrino acceleration near the neutrino sphere due to nuclear scattering caused by the Gamow-Teller neutral current interaction is shown. The effect of oscillations in the outer layers of stars significantly enhances the hardness of the spectrum of electron antineutrinos. Such an enhancement of the high-energy spectrum component is particularly pronounced for the inverted mass ordering and favorable for ground-based detection of supernova neutrinos. The possibilities of Cherenkov underwater detectors − KM3NeT and Baikal-GVD − for observation of supernova neutrinos and reveling the mass ordering are discussed.

Electron neutrinos in the T2K experiment are detected through the particles produced when they interact with matter. Charged-current interactions produce an electron, which loses energy through ionization and bremsstrahlung. This work studies the simulated energy deposition of this electron in SuperFGD, the three-dimensionally segmented scintillator detector of the ND280 complex, and examines the photon background.

A sample of 10,000 primary electrons with kinetic energies from 5 to 300 MeV was studied using Geant4. Energy deposits from the primary electron and its associated secondary particles are summed without double counting. The response is defined as the deposited energy, corrected for rest-mass energy, divided by the electron's initial kinetic energy.

When the calculation is extended from the direct electron branch to the full cascade, the mean response increases from 56.8% to 85.9%. Branches initiated by bremsstrahlung photons contribute about one third of the cascade's deposited energy on average. A primary electron stopping inside the detector does not ensure full energy containment: secondary photons can carry energy out of the active volume.

Photon conversion into an electron-positron pair was studied at photon energies of 50, 100 and 200 MeV. Under the simulated conditions, the fraction of photons converting inside SuperFGD increases from about 62% to 84% as the photon energy rises from 50 to 200 MeV. The energy deposited by conversion pairs is similar to that deposited by electrons, so electron-photon separation also requires information on the spatial structure of the event.

These results provide a basis for further development of methods for electron energy reconstruction and electron neutrino event selection. The study describes energy deposition in the active material; light collection, electronics and full neutrino event reconstruction were not included in this analysis.

The energy and timing resolution of the Russian-made Topaz-M microchannel-plate photomultiplier tube (MCP-PMT), developed and manufactured by Baspik, were experimentally studied. The coincidence time resolution of the Topaz-M MCP-PMT was measured for the first time, while its energy resolution was studied with LaBr₃:Ce and GAGG scintillators using gamma-ray sources in the 511-1275 keV energy range and compared with conventional photomultiplier tubes, assessing its potential for fast-timing and gamma-ray spectrometry applications in particle physics experiments.

This study investigates thermonuclear nucleosynthesis within hypothetical hot primordial regions of the early Universe, which are separated from the Hubble expansion and confined within domain walls. We present a numerical model simulating the evolution of nuclide concentrations at constant extreme temperatures exceeding 5 MeV. Under these conditions, the confinement of neutrinos makes weak interaction reactions reversible, leading to rapid local thermodynamic equilibrium and stabilizing both the temperature and the proton-to-neutron ratio. Our results demonstrate the formation of a unique, anomalous hydrogenless chemical composition, as practically all free nucleons efficiently bind into helium-4 (${}^4$He). Subsequently, the saturation of the plasma with helium-4 triggers an intense, explosive synthesis of carbon-12 (${}^{12}$C) via the triple-alpha process. Unlike standard stellar nucleosynthesis, this high-energy process is not solely dominated by the Hoyle resonance and is instead accurately described by the generalized Caughlan-Fowler formula, which accounts for highly excited states of the carbon nucleus. Finally, the strict conservation of the total baryon number throughout the calculations verifies the physical accuracy and stability of the applied numerical methodology.

This study presents an analysis of Nuclear Track Emulsion (NTE) exposed
to an extracted $^{124}$Xe$^{54+}$ beam at around 300 MeV per nucleon at the JINR
Nuclotron, conducted within the framework of the BECQUEREL project[1].
The primary aim was to characterize the beam profile and its uniformity, and
to determine the Bragg peak position, in support of applied research in electronic components and radiation biology. Three stacks, each consisting of 8-10 nuclear emulsion layers with a thickness of 60 µm deposited on a 2 mm thick
glass substrate were exposed transversely to the beam. This configuration enabled the recording of the ion trajectories and their energy deposition along
the penetration depth, including the stopping region and the production of long
range fragments. The area of each emulsion layer was digitally imaged using an
Olympus BX63 intelligent microscope[2]. Owing to the high ionization density
of the incident $^{124}$Xe$^{54+}$ ions, a 4X objective was sufficient for reliable track detection. A Gaussian Mixture Model (GMM) applied to the measured grain area
distributions enabled the classification of tracks into three principal groups corresponding to light fragments, intermediate mass fragments, and heavy residues,
including the primary beam ions.

References

[1] P. I. Zarubin, Lect. Notes Phys. 875, 51-93 (2014) doi:10.1007/978-3-319-
01077-9 3 [arXiv:1309.4881].

[2] J. Ronald Lawrence, JINR START Project Report,(2026). https:
//start.jinr.ru/uploads/report_files/report_student_6639_
project_1144.pdf

The uncertainty associated with reactor fission fractions is an important contribution to precision predictions of the antineutrino flux and to antineutrino-based reactor monitoring. We evaluate the uncertainties and correlations of the fission fractions of $^{235}U$, $^{238}U$, $^{239}Pu$, and $^{241}Pu$ for a VVER-1000 reactor and propagate them to the calculated electron-antineutrino flux. Burnup-dependent atomic densities and one-group microscopic fission cross sections are obtained with the Serpent Monte Carlo code and combined with BIPR-7A full-core calculations for the 13th fuel cycle of Unit 3 of the Kalinin Nuclear Power Plant. A Monte Carlo procedure is used to vary the nuclide atomic densities and fission cross sections within their adopted uncertainties, providing fission-fraction distributions, standard uncertainties, and correlation coefficients throughout a 500 effective-day fuel cycle. The correlations between the isotope fission fractions evolve significantly with burnup and are explicitly included in the uncertainty propagation. The resulting relative contribution of fission-fraction uncertainties to the antineutrino flux uncertainty increases from approximately 0.25% at the beginning of the cycle to 0.42% at the end. This contribution remains below the uncertainty associated with reactor-antineutrino spectrum models, but is comparable to the characteristic thermal-power uncertainty and should therefore be included in precision VVER-1000 antineutrino-flux calculations.

A joint study of multi-particle pseudo-rapidity correlations and event-by-event fluctuations in the distributions of secondary particles and fragments of the target nucleus and the projectile nucleus was carried out in order to search for correlated clusters of secondary particles. An analysis of the collisions of the sulfur nucleus with photoemulsion nuclei at an energy of 200 A・GeV is presented based on experimental data obtained at the SPS at CERN. The analysis of multi-particle correlations was performed using the Hurst method. A detailed analysis of each individual event showed that in events of complete destruction of a projectile nucleus with a high multiplicity of secondary particles, long-distance multi-particle pseudo-rapidity correlations are observed. The distribution of average pseudo-rapidity in such events differs significantly from others, as it is much narrower, and its average value is noticeably shifted towards lower values average pseudo-rapidity.
This research is funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP23487706).

FPGA-BASED MUON REGISTRATION CHANNEL FOR POSITIONING SYSTEM

M. A. Lapshin¹, A. V. Kantsyrev¹, A. A. Golubev¹, A.V. Bognadov¹

1NRC «Kurchatov Institute», Russia
E-mail: lapshin.mm.aa@gmail.com

Cosmic-ray muons are a natural source of penetrating particles that can be used for positioning and navigation in underground environments where conventional positioning systems have limited applicability [1, 2]. Muon-based positioning methods can use the temporal correlation of muon detection events recorded by surface and underground detectors to estimate the relative position of the underground detector.
This work presents the development of an FPGA-based muon registration channel intended for a positioning system of a borehole muon cylindrical detector [3] of muon tomography system for undeground geological object investigation or for in build positioning systems. The proposed channel is a compact reference detector located at the surface above the borehole or installed above the second muon detector for in-building systems. Its main purpose is to register the passage of a muon and generate an event timestamp in the same time reference system as the borehole detector, without the need for muon track reconstruction. The reference detector is planned to be based on a plastic scintillator and a silicon photomultiplier (SiPM), while the signal processing is performed using an FPGA (Xilinx Artix 7) operating at a frequency of 100 MHz. The surface muon registration channel and underground muon detector (of second flat muon detector) are planned to be synchronized using synchro pulse sended via suspension cable for a borehole muon detector. The resulting timestamps can be used to identify correlated muon detection events recorded by both detectors and determine the time difference between their detection. In the future, this technology can be used to estimate the angular azimutal position of the borehole detector.
The proposed approach does not require reconstruction of individual muon tracks in the reference detector and therefore allows a relatively simple detector configuration to be used. The developed system is considered as a basis for further experimental studies of the possibility of positioning borehole instruments and underground navigation using cosmic-ray muons.

References
1. Tanaka H. K. M. Muometric positioning system (μPS) with cosmic muons as a new underwater and underground positioning technique //Scientific Reports. – 2020. – Т. 10. – №. 1. – С. 18896.
2. Tanaka H. K. M. Wireless muometric navigation system //Scientific Reports. – 2022. – Т. 12. – №. 1. – С. 10114.
3. Golubev A. A. et al. Borehole muon tomograph for search and evaluation of ore deposits //Review of Scientific Instruments. – 2025. – Т. 96. – №. 11.

We propose the quark model of nuclear structure where quark correlations lead to nucleon-nucleon correlations and arrangement of them into lattice--like structure. The model is based on the quark model of nucleon structure in which valence quarks are strongly correlated within a nucleon (SCQM). Nuclei are built by junctions of SU(3) color fields of two quarks of neighboring nucleons. Application of the model to the larger collections of nucleons reveals the emergence of the face-centered cubic (FCC) symmetry at a nuclear level where nucleons arrange in alternating spin-isospin layers. The model becomes isomorphic to the shell model and composes the features of the liquid drop and cluster models. It turns out that building blocks of the nuclear structure are three-nucleon and four-nucleon configurations. These configurations form inside nuclei virtual triton, 3He and α- clusters. Applying the model to construct the isotopes of He and Li nuclei we demonstrate that ’halo’ nuclei are consequences of quark loops forming three-nucleon configurations. The model can predict the boundary of the maximal number of neutron excess, i.e. neutron drip line. Also we apply the model to analyze nucleosynthesis in stars in the framework of α-clustering.

1. G. Musulmanbekov, PEPAN Lett. № 5, p. 548 (2021); Adv. Nucl. Sci. Appl., v1, № 2, p. 105 (2025);
   https://doi.org/10.63907/ansa.v1i2.34
2. G. Musulmanbekov, Adv. Nucl. Sci. Appl., v1, № 4, p. 250 (2025);
   https://doi.org/10.63907/ansa. v1i4.53.

The High-Granularity Neutron Detector (HGND) is a new detector system in the BM@N experiment at the Nuclotron (JINR, Dubna), designed for the identification and measurement of neutron energies produced in nucleus-nucleus collisions at energies up to 4 AGeV. This talk covers progress in pre-production verification and performance studies of the full-scale active layers of the detector, as well as preparation for detector deployment. The presented data cover the timing resolution of the production version of the active layer measured with cosmic particles and an electron accelerator beam.

Flat rotation curves of galaxies suggest extra gravity at galactic scales, which is usually explained by dark matter (DM). However, astrophysicists
(P. Kroupa et al)
point to facts and data that contradict the DM hypothesis. Instead, the MOND model is advocated. The baryonic Tully–Fisher relation
$\log M_ {\rm bar} = c + b \log V_{\rm flat}$ links the baryonic mass of spiral galaxies with their asymptotic velocity. MOND requires $b = 4$. The $M_{\rm bar}$ includes stars, atomic and molecular gas (i.e. HI/HeI/H2; for dwarfs, HII component is important because intergalactic radiation ionizes HI, as N.Gnedin noted). Conducting calculations is hard and requires assumptions and/or modeling. In $[1{]}$ slope $b \approx 3$ was obtained for 32 spirals ($V_{\rm flat} \approx 45...280$ km/s; HII mass was not estimated). Slope $b = 2$ appears in modeling [2;App.G] (luminosity is square of mass, $L_{\rm gal} \approx M_{\rm gal}^2$, except for dwarfs). This slope prefers (large scale) gravity force $F \sim M_{\rm bar}/R$; some authors called it MOGA, MOdified Gravity Attraction, $[3]$. MOGA appears also in one 5$D$-variant of Teleparallelism with $4^{\rm th}$-order gravity and expanding brane-universe [4]: Newton's law turns to $F(R) = GMm/(LR)$ when $R > L$ ($L$ is the brane co-moving thickness along the extra-dimension). As it is stated in $[3]$, MOGA, unlike MOND, preserves the momentum and angular momentum, as well as stability of three-body systems.

Let's consider large scales, $R > L$. For thin disks (SO${}_2$-symmetry; plain $1/R$-model), the force in the disk plane at radius $R$, $F(R)$, depends on the mass $M_R$ inside this radius: $ F = G m M_R /(LR)$; on the axis $Z$ (uniform disc of radius $a$; 'test-mass' $m$) the attraction force is
$ \ \ F(Z) = G m M_a Z \ln(1 + a^2/Z^2) /(L a^2). \\ $
$ \ \ {\rm For}$ uniform spherical balls (bulges; radius $a$), we find:
$\ \ F(R) = G mM /(L a) \ \, f (R/a) , {\rm \ where } \\$
$ \ \ \ \ f (x) = \frac38 \{1/x + x\, –\frac12 (1/x\, – x)^2 \ln[(x + 1)/|x\, – 1|]\};$
it is maximal at $x = 1$, $f (1) = 3/4. \\ $
This function is symmetrical for the substitution $x → 1/x$, so similar series exist for small and large $x$: $\\ $
$ \ \ \ \ f (x) = x\{1 – x^2/5 – … – 3 x^{2n}/[(2n – 1)(2n + 1)(2n + 3)] – …\} = 1/x\{1 – 1/(5x^2) – … \} . \\$
One can further integrate (in parts) this function and find the potential:$\\ $
$\ \ \ \ u(x) = \int\! f (y)\, d y = \frac12 \ln|x^2 – 1| + \frac{x^2}8 – \frac{x^4 – 6x^2 – 3}{16x} \ln \frac{x + 1}{|x – 1|} + C$.

Logarithmic potential growth stops when «underdensities» appear, and cosmic voids should be objects with negative masses. Our MW galaxy resides in the KBC void (one among the largest – redshift z is small) with a shift from its center. Defocusing caused by the KBC void provides some extra-dipoles (redshift dependent). Further we are considering a simple model of spherical voids with a massive shell, which consists of two co-centered uniform balls with positive and negative densities, $\rho_b$ and $–\rho_a$, of radius $b$ and $a$, respectively.
Let the total shell mass is $M_S = \rho_b V_b – \rho_a V_a = \rho_0 V_b$, where $\rho_0 \sim 0.04 \rho_c$ is the mean baryonic density of the Universe. And take, for simplicity, $\rho_b = \rho_a$ (an absolutely empty void), and $b = \varepsilon\, a$ (with, say, $\varepsilon = 1.1$). One can can find the following void potential (again, $x = r/a$)
$ \ U(x) = GM_S L^{-1} \, u^*(x)$, where
$ \ u^*(x) = [u(x/\varepsilon ) – u(x)]/(\varepsilon^3 – 1)$.
We took into account that the uniform density $\rho_0$ gives no gravity, no potential (the case $a → 0$).
For very thin shells, $a → b$ and
$\varepsilon → 1$, we find $ u^*(x) → – x f (x)/3$ and repulsion
is ${\propto} (x f' + f)/3$.

1. Ponomareva A.A. et al. From light to baryonic mass: the effect of the stellar mass-to-light ratio on the Baryonic Tully–Fisher relation // MNRAS. 2018. V.474. 4366. hal-02117129f
2. Valageas P., Schaeffer R. The mass and luminosity functions of galaxies and their evolution // Astron. Astrophys. 1999. V. 345, 329;
   arXiv: astro-ph/9812213.
3. Toxvaerd S. Approximations and modifications of celestial dynamics tested on the three-body system. arXiv:2512.03823 [gr-qc]
   (see also arXiv:2403.02848 [astro-ph.GA]).
4. Zhogin I.L. Longitudinal waves in 5D Absolute Parallelism and relativistically expanding brane cosmology // Space, Time & Fund. Inter. 2025. No.2. 40 (Rus.; stfi.ru/en/; also see sciforum.net/paper/28941)

Heavy ions within the Galactic Cosmic Ray (GCR) spectrum present a primary challenge for radiation risk assessment in deep-space exploration and astroparticle physics. Accurate description of their biological effectiveness requires multi-scale Monte Carlo simulations that account for both nanoscale stochastic ionization patterns and macroscopic energy deposition in target volumes.

In this work, we investigate the performance and applicability of the Geant4 and Geant4-DNA toolkits for modeling the track structure of charged particles, ranging from light ions to intermediate-mass nuclei. Benchmark calculations were conducted for critical physical and nanodosimetric endpoints, specifically Radial Dose Distributions (RDD) and Ionisation Cluster Size Distributions (ICSD), across different particle energies and physics constructors.

In addition, we examine a multi-scale simulation framework to evaluate absorbed dose distributions in target geometries, accounting for particle transport through surrounding structural materials. The impact of the secondary radiation field generated along the beam path on the resulting spatial dose profile is assessed. This study demonstrates the connection between validated nanoscale track-structure metrics and macroscopic dose calculations, providing a robust methodological foundation for radiation transport modeling in space radiobiology.

Baikal-GVD is a gigaton-scale neutrino telescope deployed at a depth of about 1 km in the waters of Lake Baikal. The detector registers Cherenkov radiation using vertical strings of optical modules. Each string comprises 36 modules with a 15 m spacing, providing an instrumented length of 525 m, and a group of 8–9 such strings forms an independent cluster.

Since standard track reconstruction methods require hits in at least two strings, a significant fraction of the data remains unused. This work is devoted to the development of an algorithm for reconstructing the muon zenith angle based on information from a single string. The goal is to extend the existing track dataset with nearly vertical events and to employ independent zenith angle estimation for the suppression of atmospheric muon background.

The performance of the algorithm has been tested on simulated samples of neutrinos and atmospheric muons. It is shown that for upgoing near-vertical (with zenith angle 170°-180°) neutrinos, the median accuracy of zenith angle reconstruction reaches 1° (depending on the zenith angle and the number of hit modules).

One of the known mechanism for primordial black holes formation is based on the collapse of closed domain walls in the early Universe. The domain walls arise from multiple scalar field fluctuations during the inflationary stage. Two approaches exist for describing this process: the massless field and the massive field approximation. This paper explores both approximations. The mass spectra of the forming primordial black holes are derived and compared for both cases. In addition, the conditions of applicability for each approach are discussed.

Extreme energy release in astrophysical sources, including the Sun, is associated with the acceleration and interaction of elementary particles—specifically, with the conversion of magnetic field energy. Consequently, the systematic study of radio emission from these sources with high angular resolution makes it possible to identify the mechanisms of particle acceleration, plasma heating during flares, and energy transport processes.
This paper discusses the use of offset-focus parabolic mesh antennas (AX-Offset D90) to create the MEPhIst radio interferometer prototype and the scientific instrument itself. The MEPhIst radio interferometer will be based on two sparse-aperture antenna arrays with maximum baseline lengths of l1max ≈ 49 m and l2max ≈ 61 m. Each antenna field consists of two arrays with a special configuration and comprises up to 46 and 79 individual antenna elements (Main Antenna Modules—MAMs, based on the AX-Offset D90 antenna), respectively; the overall system dimensions are ~ 450 m, which will provide an angular resolution ranging from ~0.12° to $5.70·10-3° in the frequency range of 0.3000–6.5000 GHz. The prototype system will also consist of two arms; however, each will comprise a T-shaped array of five MAM modules with an initial maximum baseline of l0 ≈ 30 m, which can be extended to l01max ≈ 53 m and l02max ≈ 54 m, respectively. This configuration simplifies the development of techniques for image reconstruction and object coordinate determination. The low weight and compact dimensions of each individual antenna module—based on the AX-Offset D90 design—will allow the system's antenna arrays to be mounted on the roofs of MEPhI buildings using surface-laid cable runs; this will significantly reduce equipment costs compared to interferometers based on traditional parabolic antennas (which require underground cabling due to the substantial mass and size of individual antenna units).
A prototype antenna module is currently being developed and assembled at the Department of Experimental Nuclear Physics and Cosmophysics at NRNU MEPhI. Preliminary calibration has been performed at a frequency of 1.0009 ± 0.0001 GHz, and an increase in the received signal level has been demonstrated when pointing the antenna at the Sun.
One of the primary scientific objectives of the MEPhIst radio interferometer will be to study the radio emission from both solar flares and the "quiet" Sun; this will enable further research into electron acceleration mechanisms, plasma heating during flares, and energy transport processes, as well as the detection and study of shock waves and the evolution of large-scale structures in the solar atmosphere. Another application of the facility will be the development of methods for monitoring solar activity in the radio range—specifically, continuing the comparative analysis of geomagnetic events identified using various indices.
The MEPhIst radio interferometer can be used for Galactic research, including the study of the discrete radio source Sgr A, the Galactic radio halo, and neutral hydrogen clouds (HI line), as well as discrete sources and distributions in the HII (1415 MHz), H3 (1517 MHz), Na23 (1772 MHz), Al27 (1506 MHz), and OHI (1666 MHz) lines, among others; it also enables the analysis of emission properties in recombination lines.
One of the primary objectives of the MEPhIst scientific facility will be to study the properties of transient sources both within our Galaxy and beyond: investigating radio pulsar period variations (including those located in the Galactic halo), examining the characteristics of non-stationary radio emission from magnetars, and studying radio bursts that fall within the instrument's field of view. Furthermore, the instrument allows for the study of emission characteristics in the neutral hydrogen (HI) spectral line at various redshifts, making it possible to establish the principles of the Gal_z scale—an initiative aimed at resolving the discrepancy in Hubble constant (H0) values, which is a key challenge in modern cosmology. This unique new scale will be employed for the first time, complementing existing scales based on data from supernovae (SN) and the cosmic microwave background (CMB).

Secondary electron emission is the process of electron emission from the surface of a material (target) under bombardment by beams of charged particles and heavy ions. The study of this process is challenging due to the need for accurate measurements of both the incident beam current and the total current of secondary electrons emitted from the target. Secondary electron emission is a surface process, with a secondary-particle escape depth of approximately 5 nm [1]. Therefore, refractory materials coated with a thin layer of the material under investigation are commonly used as targets. A representative example is a gold-coated tungsten wire, which serves as a sensor. An array of such sensors forms a wire-grid beam profile monitor [2]. The use of this type of detector for monitoring the spatial distribution of charged particles or heavy ions extracted from an accelerator makes it possible to determine the beam profile, i.e., the transverse distribution of beam density. Beam particles interact with the sensors and eject secondary electrons from their surfaces. As a result, each sensor acts as a current source. The ratio of the total beam current to the total secondary electron current is referred to as the secondary electron emission coefficient.
In this work, a multi-wire beam monitoring system for charged particles and heavy ions, developed at Saint Petersburg State University (SPbU) [2], was used as the experimental setup. An important feature of this system is the use of sensor electrodes made of different materials and alloys. This makes it possible to determine the secondary electron emission coefficients of various materials and alloys interacting with beams of both light charged particles and heavy ions over a wide energy range.
Experimental data on secondary electron emission coefficients were obtained at the Unique Scientific Facility (USF) “A.F. Ioffe Institute of Physics and Technology U-120 Cyclotron” using 3 MeV proton beams and 53 MeV ^40Ar^8+ ion beams. During the experiments, the profiles of both beams were visualized, and the parameters of the signals generated by the sensors upon interaction with the beam particles were investigated. Processing of the experimental data allowed, for the first time, the determination of the secondary electron emission coefficients of the sensor material (gold-coated tungsten) under irradiation by proton and argon-ion beams in the investigated energy range. These results provide a basis for validating theoretical descriptions of secondary electron emission processes induced by interactions of low- and intermediate-energy charged particles and heavy ions with matter.

This work was supported by St. Petersburg State University (project ID: 153212394).

REFERENCES

1. Bronshtein I. M., Fraiman B. S. Secondary Electron Emission. — Moscow: Nauka, 1969. 408 p.
2. Zherebchevsky V. I., Zemlin E. O., Maltsev N. A. Multisensor system for monitoring charged particle and heavy ion beams. RF Patent No. 2830097, Cl. G01T 1/34 (2024.08).

For the purpose of local polarimetry at SPD, the Beam-Beam Counter system is been developing. The system is based on scintillator tiles of 10 mm thickness, produced by Uniplast company. Relative light yield, average decay time and energy resolution of the scintillator sample coupled to a PMT are measured with gamma-ray source. In this report, the results of the measurements are presented and discussed.

A prototype of a matrix pixel detector based on LYSO scintillators with EQR15-3030 type silicon photomultipliers [1] has been developed, and studies of its characteristics have been carried out. The dimensions of the detector’s scintillation elements are 3×3×20 mm; the time resolution is 150 ps, and the energy resolution is about 15% for gamma ray photon energy of 511 keV.
The coordinate coding scheme is based on the “active matrix” principle, which improves the signal-to-noise ratio during reading and significantly increases the slew rate of the output signal from the matrix, thereby improving the detector’s temporal resolution. Time parameters are measured using a multichannel TDC based on an FPGA [2]. The report will present a description of the detector, its electronics, and the results of characteristic measurements.
References
1. Measurement of Time Resolution of Scintillation Detectors with EQR-15 Silicon Photodetectors for the Time-of-Flight Neutron Detector of the BM@N Experiment / F. Guber et al. // Instrum.Exp.Tech. 67 (2024) 3, 443-446 DOI: 10.1134/S0020441224700696
2. Development of a 100 ps TDC based on a Kintex 7 FPGA for the high granular neutron time-of-flight detector for the BM@N experiment / D. Finogeev et al. // Nucl.Instrum.Meth. A 1059 (2024) 168952 DOI: 10.1016/j.nima.2023.168952

The search for CP violation in the lepton sector is one of the central goals of modern neutrino physics, motivated by the need to explain the matter–antimatter asymmetry of the Universe. In long-baseline accelerator experiments, the interpretation of neutrino and antineutrino appearance signals is complicated by matter effects: coherent forward scattering in the Earth can mimic or modify genuine CP violation. We study these effects in the T2K and NOvA experiments within the standard three-flavour oscillation picture, comparing the vacuum case with realistic matter potentials.
Using CP-odd ellipses as a visualisation tool, we scan the unknown CP phase over its full range and plot the corresponding neutrino and antineutrino probabilities. The ellipses are constructed for different values of the atmospheric mixing angle, including maximal mixing and both octants, and for several matter densities.
The parametric degeneracy between the CP phase and the octant of the atmospheric mixing angle remains a fundamental challenge. T2K provides a cleaner measurement of CP violation because its matter effect is small, whereas NOvA is more sensitive to the mass hierarchy because its matter effect is large. This complementarity makes a joint analysis essential for separating intrinsic CP violation from matter-induced asymmetries.
The next generation of long-baseline experiments, especially DUNE, will address these challenges directly. With a 1300-kilometre baseline, higher neutrino energies and a large liquid-argon detector, DUNE will experience strong matter effects and will be able to determine the mass hierarchy and search for CP violation with high sensitivity. Extending the CP-odd ellipse approach to DUNE will help optimise the separation of genuine CP violation from matter effects and clarify the role of the octant degeneracy. Together with Hyper-Kamiokande, DUNE is expected to provide a decisive test of CP violation in the lepton sector.

The next generation water Cherenkov detector Hyper-Kamiokande in its outer part will utilize light-collection modules composed of a PMT surrounded by a plexiglass-based WLS plate. Success of the rich physics program of the experiment that ranges from energetic atmospheric and accelerator and down to cosmic and solar neutrinos involves strict requirements and control of the radiopurity of the elements used in the detector. The talk presents the results of the checks of the specific activity of natural radionuclides in the samples of the WLS plates. The work was carried out in two underground laboratories of the Baksan Neutrino Observatory of INR RAS: the “NIKA‑2” facility located at a depth of 660 m water equivalent and the “SNEG” spectrometer in the DUBL‑4900 hall at a depth of 4900 m.w.e.. The measurements were performed with the HPGe-based gamma-detectors. The final sensitivity of mBq/kg was achieved. It was demonstrated that the samples of the mass-production WLS plates possess low natural radioactivity that fulfils the requirements set by the Hyper-Kamiokande physics program. The work confirms the effectiveness of the low‑background gamma‑ray spectrometry technique for the quality control of materials used in large‑scale neutrino detectors.

A modernization of the temperature control system for the M31 spectrometric magnet of the SPASCHARM experiment at the U-70 accelerator is presented. The transition to a multitasking architecture based on FreeRTOS, together with the use of EPICS, is aimed at improving the modularity, versatility, and scalability of the slow control system. The new architecture enables independent execution of measurement and communication functions and facilitates the addition of further measurement channels. As part of the system upgrade, a second branch of temperature sensors was implemented, doubling the number of monitored channels and providing complete temperature monitoring of the magnet windings.

TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) is a hybrid air-shower observatory located in Eastern Siberia and designed to study high-energy gamma rays and cosmic rays. The TAIGA-IACT imaging atmospheric Cherenkov telescopes operate at TeV energies, where a key challenge in gamma-ray observations is the suppression of the hadronic background, which significantly exceeds the gamma-ray flux.
Here we present an overview of analysis procedure used for TAIGA-IACT observations in monoscopic mode. The analysis chain is discussed, including event reconstruction, background estimation, gamma-like event selection, energy reconstruction, and the derivation of source energy spectra.

High-energy cosmic-ray muons penetrating deep underground undergo stochastic interactions in rock and can produce a significant secondary particle component accompanying the surviving muon. This effect becomes particularly important at muon energies approaching the PeV range, where radiative and photonuclear processes may result in large energy transfers and production of energetic secondary particles. In this work, Monte Carlo simulations of high-energy muon propagation through the rock overburden of the Gran Sasso underground laboratory are performed. The characteristics of the muon and secondary particles emerging from the rock are studied as a function of the initial muon energy. The analysis includes the residual muon energy, secondary-particle multiplicity and total energy, as well as the contributions of electrons and positrons, hadrons, and secondary muons. Particular attention is paid to the formation and evolution of the particle accompaniment generated by stochastic muon interactions in the rock. The obtained results are relevant for the interpretation of high-energy muon events in deep underground detectors and for studies of the response of the LVD setup to the highest-energy component of the underground cosmic-ray muon flux.

Machine-learning-based calorimeter reconstruction is usually optimized under fixed detector conditions, whereas detector response can be affected by dead channels, local readout failures, gain drift, and noise. We study whether exposing a reconstruction model to several simulated failure modes during training improves its robustness compared with training on a single corruption type. The study uses 533-voxel charged-pion showers from CaloChallenge Dataset 1 and a layer-gated Transformer supplied with voxel energies and operational masks. Two models with identical architecture were trained: one exclusively on events with 5% randomly disabled cells, and one on an equal mixture of clean events, random cell loss, contiguous dead-cell blocks, and complete-layer failures. Evaluation was performed on an independent sample of 120,800 showers under clean, familiar, and unseen detector distortions. Multi-scenario training reduced relative mean absolute error from 0.1804 to 0.1533 on clean events, from 0.1799 to 0.1610 for block failures, and from 0.1940 to 0.1751 for a mixed unseen corruption. For physically consistent complete-layer loss, uniform layer-averaged rMAE decreased from 0.2404 to 0.1929, while voxel-weighted rMAE decreased from 0.2844 to 0.2104. The gain was not universal: the single-corruption regimen remained competitive near its specialized random-cell-loss condition. These results show that multi-scenario failure training improves broad robustness of charged-pion energy reconstruction while preserving a trade-off between generalization and narrow specialization.

Muonography is an innovative method for investigating the internal structure of massive natural and industrial objects using fluxes of high-energy atmospheric muons. Its range of applications is broad, extending from mineral exploration to the assessment of natural and man-made risks to civil infrastructure. In geology and geophysics, it serves as a promising tool that complements traditional approaches and acts as an independent experimental method for forecasting seismic and volcanic processes, as well as for assessing deformation in fault, landslide, and karst zones. The paper presents the first geoecological experiment conducted at Mount Bytkha (Sochi), involving the modeling and optimization of detectors to identify zones of fracturing.

Muon reconstruction in the Baikal-GVD neutrino telescope requires inferring particle parameters from sparse, irregularly distributed optical signals. We investigate graph neural networks and transformer architectures for reconstructing muon direction and track position, using classical track fitting as a reference. Muon energy estimation is considered as an additional task.

Using Baikal-GVD events simulated with NTSim, we will compare reconstruction accuracy and computational efficiency under common evaluation conditions. The neural models will use detector geometry and the spatial and temporal structure of optical signals. We will also explore whether joint estimation of energy and track parameters improves reconstruction.

The comparison will examine how reconstruction errors depend on event characteristics and identify conditions in which the methods offer complementary strengths. This will help assess the trade-off between accuracy and computational cost when selecting reconstruction methods for Baikal-GVD.

A number of current and future neutrino experiments are devoted to the detection of astrophysical neutrinos. Neutrino interactions with dense matter and strong magnetic fields peculiar to astrophysical environments, such as supernova explosions, are expected to cause considerable effects in the neutrino flavour evolution. One of the interesting effects is damping of the neutrino oscillations due to the neutrino wave packets separation. We develop the wave packet description of neutrino oscillations in astrophysical environments. It is shown that the damping of neutrino helicity transitions caused by their interactions with a magnetic field can occur during supernova explosions. We emphasize the difference between Dirac and Majorana neutrinos. CP-violating effects are also considered.

Based on:
[1] A.Popov, A.Studenikin, “High-energy neutrinos flavor composition as a probe of neutrino magnetic moments”, Phys.Rev.D 111 (2025) 12, 123001.
[2] A.Popov, A.Studenikin, A.Tcvirov, "Wave packet description of Majorana neutrino oscillations in a magnetic field", arXiv:2602.02804.
[3] A.Popov, A.Studenikin, “Manifestations of nonzero Majorana CP-violating phases in oscillations of supernova neutrinos”, Phys.Rev.D 103 (2021) 11, 115027.

The T2K long-baseline neutrino experiment studies neutrino oscillations using a beam produced at J-PARC, the near-detector complex ND280, and the Super-Kamiokande far detector. The upgraded ND280 includes the Super Fine-Grained Detector (SuperFGD), a highly segmented plastic-scintillator target with three-dimensional readout and precise timing capabilities. These features make SuperFGD particularly suitable for neutron studies, since neutrons do not leave a direct ionization track before interacting.

This work presents a Monte Carlo study of neutron transport and energy reconstruction in SuperFGD. First, monoenergetic neutron samples were used to study flux attenuation as a function of detector depth and neutron kinetic energy. An energy-dependent neutron interaction cross section was extracted using the positions of first interactions and compared with the published SuperFGD prototype measurement on hydrocarbon.

The analysis was then extended to charged-current muon antineutrino interactions inside SuperFGD. Events were classified by interaction mechanism and final-state topology, with particular attention to neutron-containing final states. For each primary neutron, its kinetic energy was reconstructed using the flight distance and time interval between its production point and first hadronic interaction. For neutrons whose first hadronic interaction occurs inside the active detector volume, the TOF-reconstructed kinetic energy shows a strong correlation with the true value. A major limitation at the truth level is the finite detector volume, since some neutrons leave SuperFGD before interacting.

The TOF-reconstructed neutron energies were then used in a simplified truth-level calorimetric reconstruction of the incident muon antineutrino energy. The result was compared with an otherwise identical estimator using the true neutron kinetic energies. The comparison shows that TOF reconstruction introduces only a small additional energy bias. This demonstrates the potential of neutron time-of-flight information for accounting for the energy carried by neutrons in charged-current antineutrino events. The remaining energy imbalance requires further study, including the role of nuclear effects and the treatment of the final state. Future work will also include detector response, finite timing resolution, detection thresholds, and hit-level reconstruction.

Neutron-induced fission of 232-Th: calculation of the reaction cross-section

A.K. Grigoriev

National Research Nuclear University MEPhI, Moscow, Russia

This work investigates the feasibility of reproducing the dependence of the ²³²Th fission cross-section on incident neutron energy in the 0.1-40 MeV range using the TALYS-2.2 code [1]. This study represents the first stage of a project aimed at describing the differential fission cross-section - or, equivalently, the angular distribution of fission fragments - defined as the ratio of the differential cross-section to the total cross-section (integrated over all fragment emission
angles). While the fission cross-section is primarily determined by the shape of the fission barrier and the nuclear level density at the barrier, the angular distribution depends on the distribution of these states with respect to the projection K of the nuclear spin onto the axis of elongation of the fissioning nucleus (see, e.g., [2]) - a characteristic to which the fission cross-section itself is insensitive. Insights into the distribution of the quantum number K derived from experimental data could accelerate the development of modern approaches to modeling the dynamics of fissioning nuclei with non-zero spin.

The ²³²Th nucleus is one of the few for which experimental data exist regarding the energy dependence of not only the neutron-induced fission cross-section (see, e.g., [3]) but also the angular anisotropy of fission fragments [4, 5]. Additional interest in the ²³²Th nucleus stems from experimental evidence indicating the existence of a third hump in the fission barrier of the compound nucleus ²³³Th. However, it has been found that calculations performed using the TALYS-2.2 code with default parameters yield an overestimated fission cross-section.

To refine the description, the heights and widths of the fission barriers were varied for the compound nucleus ²³³Th and for thorium isotopes with mass numbers 232-228, whose fission contributes to the observed total fission cross-section via the (n,1nf)-(n,5nf) channels. The sensitivity of the fission cross-section to the excited-level density and the shape of the fissioning nuclei at the barriers was also investigated. A triple-humped barrier model for ²³³Th provides a smooth overall description of the energy dependence of the fission cross-section; however, a double-humped barrier parameterization yields similar results, leaving the question of the necessity of a third hump unresolved. The resulting parameter values ​​can serve as a basis for the next stage of the work: calculating the differential cross-section for the ²³²Th(n,f) reaction.

1. A.J. Koning, S. Hilaire, S. Goriely. EPJA, v. 59, p. 131 (2023).
2. R. Vandenbosch, J.R. Huizenga. Nuclear Fission. - New York, Academic Press, Inc., 1973.
3. O.A. Shcherbakov et al. JNST, v. 39, suppl. 2, p. 230 (2002).
4. I.V. Ryzhov et al. Nucl. Phys. A, v. 760, p. 19 (2005).
5. Vorobyev A.S. et al. JETP Letters, v. 102, p. 203 (2015).

Isotope and velocity distributions of neutron-rich isotopes produced in peripheral heavy-ion collisions are investigated using the high-luminosity, strong-focusing kinematic fragment separator COMBAS at the U400M cyclotron facility. Full systematic study of the short-lived isotopes produced in collisions induced with 18O (at 35 MeV/nucleon), 22Ne (at 42 MeV/nucleon), and 40Ar (at 36 MeV/nucleon) primary beams on 9Be and 181Ta targets are presented. Experimental data were compared with model predictions, namely, empirical parametrization of fragmentation cross-sections (EPAX), the abrasion–ablation (AA) model and combined transport-statistical approach (BNV – SMM) to evaluate the accuracy of the model predictions and suggest the ways for improving them.

IGR J17285−2922 is a very faint transient low-mass X-ray binary whose compact object has not yet been securely identified. Its consistently hard X-ray spectra during detected outbursts and its multiwavelength behaviour favour a black hole interpretation, although a neutron star primary has not been excluded. We investigate the nature of the compact object using two archival NICER observations obtained during the 2019 outburst that were not included in previous studies, providing a total cleaned exposure of approximately 3 ks. Our analysis combines X-ray spectroscopy with high-time-resolution variability diagnostics. The NICER energy spectra are compared with quasi-simultaneous Swift/XRT measurements to characterize the X-ray flux and spectral state of the source. Energy-resolved power-density spectra, broad-band fractional variability, and searches for coherent pulsations and quasi-periodic oscillations are used to investigate compact-object-sensitive timing signatures. Particular attention is given to high-frequency variability and possible thermal emission consistent with a neutron-star surface or boundary layer. Together, these independent spectral and timing diagnostics provide a new test of the black hole and neutron star interpretations of IGR J17285−2922 and help refine the classification of this very faint X-ray binary.

A prototype for the BBC subsystem was mounted at the Internal Target Station (ITS) of the Nuclotron/NICA accelerator complex and tested with ¹²⁴Xe beam at an energy of 2.2 GeV/nucleon. Two sectors, each consisted of 8 scintillation tiles, were tested using with the full data acquisition system based on the FERS5200 electronics.

The study describes the data obtained in both trigger and triggerless modes. The contribution of the detected nuclear fragments are clearly identifiable on the energy deposition correlation histograms. This result demonstrates the system’s efficiency and becomes an important step toward the development of the BBC subsystem for the upcoming SPD experiment.

The report presents the results of a study of the processes of paired gravitino production at the Large Hadron Collider (LHC). The observability of such processes under LHC conditions is assessed. In the model under study, the gravitino is the LSP and is also considered a candidate for a dark matter particle.

The study examines the applicability of the commercially available silicon PIN photodiode BPW34 without internal amplification as a photodetector for scintillation light. Specifically, the photodiode response to cosmic-muon-induced light flashes is investigated when optically coupled to a bismuth germanate crystal (BGO) and a plastic scintillator. The electronic readout is utilized as a means of measuring and evaluating this response. During external triggering from an independent silicon photomultiplier channel (SiPM), synchronized photodiode signals are observed for both the plastic and BGO scintillators. The obtained oscilloscope traces demonstrate that BPW34 can serve as a low-cost alternative to photodetectors with internal amplification for a limited class of scintillation applications where the expected light signal is sufficiently large and a time resolution better than approximately 100 ns is not required. The current results therefore establish a baseline for signal visibility in these geometries, while indicating the need for future quantitative measurements of single-event registration efficiency.

Polymer Composite Scintillators Based on Halide Perovskite Nanocrystals for X-Ray Imaging

A. A. Knysh$^1$$^,$$^2$, P. M. Sokolov$^1$$^,$$^2$, V. V. Sosnovtsev$^1$, P. S. Samokhvalov$^1$$^,$$^2$

$^1$National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, 115409 Russia

$^2$Life Improvement by Future Technologies (LIFT) Center, Moscow, 121205 Russia

The performance of indirect X-ray imaging systems depends on the ability of a scintillator to efficiently convert X-rays into visible light while preserving the spatial distribution of the transmitted radiation. High-resolution imaging therefore requires efficient X-ray absorption and radioluminescence (RL) combined with thin, optically homogeneous scintillation layers. Metal-halide perovskites are promising for this purpose due to their strong X-ray absorption, efficient photoluminescence (PL), and compatibility with solution-based fabrication [1]. In particular, CsPbBr$_{3}$ perovskite nanocrystals (PNCs) exhibit a high effective atomic number Z$_{eff}$ ≈ 63.2) and PL quantum yields approaching 100% [2], while their incorporation into polymer matrices enables the fabrication of thin-film composite scintillators.

In this work, thin-film scintillators based on CsPbBr$_{3}$ PNCs embedded in a modified poly(methyl methacrylate) (PMMA) matrix were fabricated and tested for X-ray imaging. Films with thicknesses up to approximately 500 μm were found to be preferable for high-resolution imaging. A dedicated experimental setup was assembled in which the radiographic image was formed by the X-ray shadow of the investigated object projected onto the scintillator surface and converted into visible emission. The image was recorded using a conventional digital camera (Canon EOS R6 Mark II), with an Apogee 5500 Series X-ray tube operated at 50 kV as the radiation source. Using a TYP 39-A test pattern with 0.03-mm-thick lead lines, a spatial resolution of approximately 8-9 lp/mm was achieved at an exposure time of 5-10 s.
The thermal stability of both PL and RL intensities was also investigated. Only a minor decrease in emission intensity relative to its initial value was observed after the heating-cooling cycle. Radioluminescence remained detectable even at 445 K, while the relative decline of RL intensity was lower than that of CsI:Tl, BGO and GAGG:Mg,Ce over the investigated temperature range.

Overall, the results demonstrate the potential of CsPbBr$_{3}$/polymer thin-film scintillators for high-resolution X-ray imaging using a simple optical readout scheme.

Keywords: scintillators, CsPbBr$_{3}$, radioluminescence, X-ray imaging, spatial resolution.

REFERENCES

1. Yang, Z. et al. Designer Bright and Fast CsPbBr$_{3}$ Perovskite Nanocrystal Scintillators for High-Speed X-Ray Imaging. Nat Commun 2024, 15 (1), 8870.
2. Knysh, A. et al. Principles of Chemical Designing of Styrene-Based Plastic Scintillators Doped with Quantum Dots. Phys. Atom. Nuclei 2024, 87 (11), 1744–1749.

The Baikal-GVD neutrino telescope is situated in Lake Baikal at depths of $750$ – $1275$ m. Its current instrumented volume is $0.8$ km$^{3}$, and it is being expanded toward $1$ km$^{3}$. Baikal-GVD is capable of detecting neutrinos in TeV-PeV energy range, including those of astrophysical origin. Previously Baikal-GVD has demonstrated an observation of astrophysical neutrino flux in the cascade detection channel. Present work focuses on development of likelihood-based analysis technique aimed at the diffuse astrophysical neutrino flux search using muon track detection channel. Preliminary results on its sensitivity analysis are presented.

In a baryon-asymmetric Universe, primordial antimatter domains arise from inhomogeneous baryogenesis driven by the Pseudo-Nambu-Goldstone Boson field during inflation. Their evolution is governed by the competition between Hubble expansion and microphysical erosion of the domain boundary via annihilation with surrounding matter.
The domain, however, is not homogeneous. Stochastic dynamics of the phase during inflation causes repeated recrossings of the potential barrier, producing a self-similar nested hierarchy: antimatter domains containing baryonic inclusions, which themselves contain antibaryonic inclusions, and so on down to the horizon scale at the end of inflation.
The key consequence for nucleosynthesis is that annihilation proceeds throughout the volume, not on a single outer boundary. At t =100 s, free neutrons diffuse to the internal interfaces and annihilate there, suppressing primordial helium-4. High-energy photons from pion decay photodissociate helium-4 nuclei, significantly raising the helium-3 to helium-4 ratio, while non-thermal reactions overproduce lithium-6. This provides a unique chemical signature for antimatter astrophysical objects such as anti-stars or globular clusters. On the other side nonhomogeneity of antimatter domain facilitates formation of antimatter objects of stellar mass, which can be source of antihelium-4 in cosmic rays.
Current models predict an anti-helium flux within reach of the AMS-02 experiment. Consistency with cosmic microwave background and diffuse gamma-ray observations sets a strict upper limit on the fraction of annihilated antimatter, imposing strong constraints on models of inhomogeneous baryogenesis.

Lorentz invariance violation (LIV) can modify electromagnetic interactions at ultra-high energies and thereby affect the development of extensive air showers (EASs). We study a subluminal photon-sector LIV scenario in which Bethe–Heitler pair production is suppressed. Using LIV-modified EAS simulations, we model the resulting changes in the depth of shower maximum, $X_{\max}$, and reconstructed energy. The predictions are folded with the published Pierre Auger Observatory fluorescence-detector response and compared with the measured $X_{\max}$ distributions, allowing the primary composition to vary. Within this simplified analysis, we obtain the 95% confidence-level constraint $M_{\rm LIV}>1.5\times10^{21}\,\text{GeV}$, where $M_{\rm LIV}$ is the characteristic LIV energy scale in the photon sector. This result demonstrates the potential of hadron-induced EASs for probing photon-sector LIV.

This work was supported by the Russian Science Foundation, grant 22-12-00253(P). The speaker acknowledges a PhD student fellowship from the Theoretical Physics and Mathematics Advancement Foundation “BASIS” under contract 24-2-10-39-1.

The report describes a proportional counter developed for the search for cold dark matter, presumably consisting of hidden photons, in the PHELEX experiment (PHoton-ELectron EXperiment). The two-cathode counter is aimed at searching for diurnal variations in the count rate of single electrons emitted from the surface of the metal cathode of the proportional counter, presumably as a result of the photoelectric effect caused by the conversion of dark photons on the surface of the metal cathode. Measurement results and directions for possible further development of the experiment based on the developed counter are presented.

The processes of solar neutrino scattering by the H and He atoms are considered. Along with the weak neutrino-electron interaction, the electromagnetic interaction due to the neutrino magnetic moment $\mu_\nu$ is also taken into account. This study can be useful for the analysis of data from neutrino as well as dark matter experiments. Specifically, it could be useful to estimate the irreducible solar background in the SArov Tritium-Ultra-Reach Neutrino Experiment (SATURNE), which is under preparation within the scientific program of National Center for Physics and Mathematics. One of the main goals of SATURNE is the search for the neutrino magnetic moment, which is the most studied among neutrino electromagnetic (EM) properties and the discovery of which will open a window to physics beyond Standard Model (SM). For this purpose, a high-intensity tritium source of electron antineutrinos will be employed in combination with different detectors, including the detector based on He-II.
We calculate numerically the SM and EM neutrino-electron and neutrino-atom recoil spectra in the He detector in SATURNE for the case of solar neutrinos arising from the solar nuclear reactions. The obtained event rates are used to estimate the detector sensitivity to $\mu_\nu$ of solar neutrinos.
In addition, we study the differential cross sections of tritium neutrino scattering by electrons in the H atoms and outline characteristic deviations from the customary free-electron approximation.

In various microscopic string models (see, e.g., [1–8]), the Schwinger mechanism [9, 10]—which features a characteristic Gaussian exponential—is used to describe particle transverse-momentum spectra. On the other hand, experimental data on inclusive hadron production spectra exhibit pronounced thermal behavior. A. Bialas [11] proposed resolving this contradiction by accounting for fluctuations in the string tension k, modeled by a Gaussian distribution. However, the probability distribution proposed in [11] peaked at k = 0, which seems physically incorrect in the context of QCD confinement: a string possesses finite average energy density, so the probability of zero tension should vanish. In the present work, we modify the Bialas approach by assessing the local string tension fluctuations around its mean value. We demonstrate that not only the mean value of the string tension but also its fluctuations influence the strangeness production, and the treatment of these fluctuations allows for a better description of strange particle yields.

The authors acknowledge Saint-Petersburg State University for a research project ID: 153212394

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The possible formation of deconfined quark matter in the cores of massive neutron stars and magnetars provides an extreme environment for studying quarkonium in ultra-strong magnetic fields. In this work, quarkonium states and their annihilation through the q q̅ → 2γ channel in hot magnetized quark matter are investigated, taking into account Landau-level quantization and the interaction with the surrounding thermal quark-antiquark medium. The thermal quark-antiquark pairs are assumed to be produced through the decay (timelike splitting) of virtual gluons in the deconfined medium.

An analytical description of the annihilation width is developed, with an extended formulation including the full Landau-level structure, screened interactions, and relativistic thermal averaging. In the lowest-Landau-level ultrarelativistic limit, the thermally averaged width scales as <Γ> ∝ T⁴. In the light-quark limit, the two-photon annihilation channel is related to the π⁰ → 2γ decay, with a characteristic width of order 10 eV. Order-of-magnitude estimates give annihilation times of ~10⁶ years for light quarks and ~1.5×10³ years for heavier quarks with m_q ≥ 100 MeV.

The light-quark timescale is comparable to the characteristic ~10⁶-year magnetic-field evolution timescale of a stable magnetar, whereas heavy-quark states can annihilate much faster. This suggests that the q q̅ → 2γ channel may play a more pronounced role in the thermalization of deconfined matter for heavier quarks during the evolution of strongly magnetized compact astrophysical objects.

The results of research of semiconductor detectors made of silicon carbide (SiC-SCD) [1-3] and silicon (Si-SCD) are presented. The irradiation was carried out using a standard spectrometric α‑source 226‑Ra with energies E = 4.8; 5.5; 6.0; 7.7 MeV. The thickness of the sensitive layer of the SiC detectors of n‑type was 25 μm and 50 μm, and the diameter of the working area was 3.0 mm. The initial energy resolution of the detectors was 25 keV. The Si detectors were manufactured using planar technology from n‑type silicon with a working area of 7 mm^2 and a sensitive thickness of 100 μm. The radiation hardness of SiC and Si detectors was studied before and after irradiation with alpha particles at integral fluxes up to ~ 2×10^11 α/cm^2. It was shown that degradation was ob-served after irradiation: the peaks from alpha particles shifted towards the lower channels and be-came wider. It was found that as the radiation dose increased, the energy resolution deteriorated by more than an order of magnitude for SiC‑SCD 50 μm, by a factor of 4 for SiC 25 μm, and by more than a factor of 2 for Si‑SCD. At the same time, the charge collection efficiency (CCE) decreased from 100% to 80% (operating voltage 300 V) for SiC‑SCD 50 μm, from 100% to 90% (operating voltage 200 V) for SiC‑SCD 25 μm, and from 100% to 95% (operating voltage 100 V) for Si‑SCD at the maximum irradiation dose.

1. S.A. Evseev et al. // Physics of Atomic Nuclei. 2023. V. 86, No. 5, pp. 841–844.
2. Yu.B. Gurov et al. // Instrum. Exp. Tech. 2024, V. 67, No. 6, pp. 1095–1101.
3. S.A. Evseev et al. // Physics of Atomic Nuclei. 2025. V. 88, No. 3, pp. 489–493.

Abstract

Subthreshold production of ΛΛ pairs in nucleus–nucleus collisions is largely unexplored and is of particular interest for studying strangeness-production mechanisms in dense baryonic matter.

In 2023, the fixed-target BM@N experiment at the NICA–Nuclotron accelerator complex collected data from Xe + CsI collisions at a beam kinetic energy of 3.8A GeV. This work presents the procedure used to reconstruct Λ hyperons and extract the ΛΛ signal from these data.

Λ hyperons are reconstructed via the weak decay Λ → pπ⁻ using a displaced-vertex topology, with the secondary decay vertex separated from the primary interaction vertex. Events containing two Λ candidates are analysed using the two-dimensional distribution of the invariant masses of the two pπ⁻ combinations. The number of events containing ΛΛ pairs is determined by estimating the contribution from combinatorial background in the two-dimensional invariant-mass plane. The stability of the extracted ΛΛ signal is assessed by varying the Λ-candidate selection criteria and the methods used to model the combinatorial background.

Stochastic dynamics of a scalar field evolving according to the nonlinear Kardar–Parisi–Zhang (KPZ)
equation and interacting with a randomly moving incompressible fluid is investigated.
The fluid dynamics is described by the stochastic Navier–Stokes equation with an external random force.
In a difference with previous studies, an active feedback reaction of the growing surface profile
on the fluid velocity field is included. The analysis is performed within the field-theoretic approach
and Renormalization Group (RG) framework. Renormalization constants, $\beta$-functions, and anomalous
dimensions are calculated in the one-loop approximation using dimensional regularization and Minimal
Subtraction (MS) scheme. Fixed points of the RG equations are found, and their infrared (IR) stability
is examined via eigenvalues of the stability matrix. The main physical result is that at the only
IR-attractive fixed point, the coupling constant corresponding to the active feedback of the scalar field
on the fluid vanishes. This means that at macroscopic spatial and temporal scales, turbulent mixing
dominates and suppresses the hydrodynamic response induced by the growing surface.

We investigate resonance phenomena in kink-antikink collisions in
(1+1)-dimensional scalar field theories with higher-order polynomial
potentials. Particular attention is paid to the mechanism of energy
exchange between the translational motion of the kinks and vibrational
modes of the kink-antikink system.

Numerical simulations reveal a nontrivial dependence of the collision
outcome on the initial velocity of the kink and antikink. In addition
to kink–antikink capture and one-bounce escape, narrow multi-bounce
resonance windows are observed. Within these windows, part of the
kinetic energy of the kinks is transferred during the first collision
into vibrational excitations of the kink-antikink system and can
subsequently be transferred back into translational motion. This
allows the kink and antikink to escape after two or more collisions
for initial velocities below the critical velocity.

The structure of the resonance windows, the critical velocities, and
the spectral properties of kink-antikink configurations are analyzed.
The numerical results support the resonant energy exchange mechanism
as an explanation for the formation of the observed resonance windows.
In particular, the resonance structure can be interpreted in terms of
energy exchange between the translational motion of the kinks and
collective vibrational modes of the kink-antikink pair.

One of the scientific goals of the LVD experiment is the search for neutrinos. The study of neutrinos is important for understanding particle physics and processes occurring in astrophysical objects. In this work, high-energy single-muon events are considered under the assumption that some upward-going events may be related to interactions of muon neutrinos.
An algorithm was developed to convert the direction of a muon registered in the local LVD coordinate system into coordinates in the ICRS system. The algorithm then searches for possible astrophysical sources from the 4FGL-DR4 catalog within a selected angular distance. The 4FGL-DR4 is a catalog of gamma-ray sources based on 14 years of Fermi-LAT observations of the whole sky. Objects from this catalog are considered as possible candidates for high-energy neutrino sources.

Semiconductor radiation detectors provide high energy resolution, with silicon PIN photodiodes being widely utilized due to their technological simplicity and affordability. This study investigates the feasibility of using the commercially available BPW34 silicon PIN photodiode as a low-cost semiconductor detector for X-ray and soft gamma-ray spectrometry. A method for determining the optimal reverse bias voltage was developed based on the analysis of $^{241}\text{Am}$ energy spectra. The optimal operating voltage was established at 60 V, ensuring the formation of a depletion region sufficient for complete charge collection while minimizing noise. Spectra of $^{241}\text{Am}$, $^{133}\text{Ba}$, $^{137}\text{Cs}$, and $^{152}\text{Eu}$ sources were measured at room temperature using an experimental setup comprising a charge-sensitive preamplifier and an SBS-79 spectrometric analyzer. A linear calibration was performed based on photopeak positions within the energy range from 5 to 120 keV. The detector's energy resolution (FWHM) was found to be between 1.26 and 1.96 keV, depending on the gamma-ray energy. The results confirm the linearity of the response and the stable operation of the BPW34 PIN photodiode in spectrometric mode, making it a promising, cost-effective alternative to specialized detectors for scientific and educational applications.

In spite of the fact that nuclear track emulsion (NTE) was developed more half a century ago, it still remains a universal and cost-efficient detector. The application of NTE is especially well grounded where tracks of nuclear particles cannot be reconstructed using electronic detectors. At the JINR Nuclotron the BECQUEREL experiment [1] is performed a program of irradiation of NTE stacks in the beams of relativistic isotopes of beryllium, boron, carbon and nitrogen, including radioactive ones to study their cluster structure. Сharge-topology distributions of final states have an individual character appearing to be some kind of a signature of the isotope under study. The NTE technique allows one to observe the 3D images of few-body ensembles originated in peripheral collisions and explore the fragmentation of the relativistic nuclei down to the most peripheral interactions - nuclear “white”stars [2].
The competitive character of the novel NTE is proved in measurements of slow α particles and heavy ions (summarized in [3]). The possibility of α spectrometry was verified and the atom drift effect is established in measurement of decays of 60 MeV 8He nuclei implanted in NTE [4]. Correlations of α particles in splitting of 12C nuclei by 14.1 MeV neutrons [5] as well as 7Li and 4He nuclei produced in 10B breakup by thermal neutrons in boron-enriched NTE [6] are studied. NTE samples were irradiated with slow Kr and Xe ions [7,8]. Surface irradiations of NTE samples were performed with automatic movement of the 252Cf source [9].Thus, the connection of high energy and low energy nuclear physics appears. Classic observations of fundamental importance presented in “The Study of Elementary Particles by the Pho-tographic Method”by C. H. Powell, P. H. Fowler and D. H. Perkins can serve as a model of clarity in our time. Our research is implemented in keeping with this tradition by state-of-art means. The rich collection of videos and images of the nuclear few-body processes gathered at the Web site is presented [1]. In terms of applications they are relevant for the development of advanced systems of automatic search for nuclear interactions, as well as for university education.

References
1. The BECQUEREL Project WEB site: http://becquerel.jinr.ru/
2. http://becquerel.jinr.ru/movies/movies.html
3. P. I. Zarubin “Recent applications of nuclear track emulsion technique”Phys. At. Nucl., 2016, 79, 1525-1535; DOI: 10.1134/S1063778816130093. https://link.springer.com/article/10.1134/S1063778816130093
4. http://becquerel.jinr.ru/miscellanea/8He/8He.html
5. http://becquerel.jinr.ru/miscellanea/DVIN/dvin11.html
6. http://becquerel.jinr.ru/miscellanea/IBR-2/IBR-2.html
7. http://becquerel.jinr.ru/miscellanea/IC-100/IC-100.html
8. http://becquerel.jinr.ru/miscellanea/U400M/U400M.html
9. http://becquerel.jinr.ru/miscellanea/Prague-dosimetry/Prague-dosimetry.html

The gas of thin tubes of a massless scalar field (TToMSF) could have been formed at the earliest stages of the evolution of the Universe and, as a result, could have influenced all processes in its evolution. The feature of TToMSF gas is that the parameter of the equation of state of such a gas depends on the density of the gas. As a result, local equations of state can be realized in TToMSF gas; this may alleviate tensions within the standard cosmological model associated with the inhomogeneity of structure growth in the Universe and the significantly higher inhomogeneity of the observed Universe. At the same time, the gravitational interaction between individual TToMSFs in the gas can lead to the generation of particles with an effective non-zero rest mass, which, taken together, allows us to classify the TToMSF gas not only as a dynamical dark energy model, but also as a unified dark fluid model. In this work, we investigated possible trajectories of a test null string in the gravitational field of an early’’ thin closed tube of a massless scalar field that radially increases or decreases its size. We have shown that the test null string experiences astrong'' gravitational attraction at each segment of its trajectory, which is capable of changing the nature of the motion of the test null string to the opposite. This feature of interaction may indicate the possibility of realizing a scenario of long-term self-consistent motion of two closed TToMSFs within a spatially limited region. At the same time, such gravitating systems can be interpreted as particles with an effective non-zero rest mass.

This work presents the results of an experiment performed at the ACCULINNA-2 fragment separator (FLNR JINR) aimed at studying the elastic and inelastic scattering of ^{6}He + ^{4}He over a wide angular range. A secondary 6He beam with an energy of 151 (168) MeV irradiated a 5.5-mm thick cryogenic gaseous ^{4}He target maintained at a temperature of 12 K and a pressure of 1 (2) atm. The reaction products were registered in a two-arm geometry using the detector system described in [1].
The primary objective of the investigation was to determine the differential cross sections for the ^{6}He + ^{4}He → ^{4}He + ^{6}He(g.s.) and ^{6}He + ^{4}He → ^{4}He + ^{6}He(2+) channels. For the channel populating the ground state of 6He, the angular distribution in the center-of-mass system (c.m.s.) was obtained across a wider angular range and with better resolution than in previous measurements [2]. In particular, new data were obtained for Θ_{c.m.s.} ~ 15°–60° and, most notably, for the Θ_{c.m.s.} ~ 130°–165° range, which corresponds to the two-neutron transfer reaction mechanism. The angular distribution for the channel involving the excitation of the 6He(2^{+}) state was extracted by selecting events with the simultaneous detection of two alpha particles. Consequently, the angular dependence of the cross section in the 130°–165° region was obtained for the first time. The optical model was applied to describe the data at forward angles, whereas the FRESCO and DWUCK5 codes were utilized for the backward angles.
In addition, the spectrum of highly excited states of 6He, obtained via the missing mass method in the ^{6}He + ^{4}He → ^{4}He + ^{6}He* (^{4}He+n+n) reaction, was analyzed separately. It is demonstrated that this spectrum is formed by the contribution of a peak corresponding to the 2^{+} state at E_{ex} = 1.8 MeV, alongside a long "tail" most likely attributed to negative parity states. In the ^{4}He–t coincidences, a peak presumably associated with the dipole mode was observed at E_{ex} = 26–27 MeV, which is induced by the breakup of the alpha cluster in 6He. The mechanism underlying the emergence of potential background events at excitation energies of 15 MeV and above, as well as methods for their elimination, are discussed.
References
1. A. A. Bezbakh, S. G. Belogurov, V. Chudoba et al., Detector Array for the 7H Nucleus Multi-Neutron Decay Study, Phys. Part. Nuclei Lett. 20, 629–636 (2023).
2. G. M. Ter-Akopian, A. M. Rodin, A. S. Fomichev et al., Two-neutron exchange observed in the ^{6}He+^{4}He reaction. Search for the "di-neutron" configuration of 6He, Phys. Lett. B 426, 251–256 (1998).

DANSS is a highly segmented antineutrino detector located at the Kalinin Nuclear Power Plant. The main goal of the experiment is to search for reactor antineutrino oscillations into a hypothetical sterile neutrino state. DANSS has achieved the most stringent model-independent limits around Δ𝑚₁₄² ≈ 1 eV². The experiment searches for reactor antineutrino oscillations into a sterile state by analyzing the spectrum of positrons produced by antineutrinos in inverse 𝛽-decay (since almost all of the antineutrino energy is transferred to the positron in this reaction). Therefore, the accuracy of the detector's energy scale calibration is crucial.
The DANSS sensitive volume consists of 2,500 scintillation strips, each read by a separate silicon photomultiplier (SiPM). A group of 50 strips is also read by a single PMT. The SiPM response becomes nonlinear at high light signals due to a limited number of pixels. This nonlinearity can be described using the effective number of pixels. In this study, we explore the possibility of improving detector energy calibration by taking into account individual values of the effective pixel number for each SiPM determined using signals from muons crossing a scintillator strip at different angles. We use the full dataset accumulated over ten years of DANSS operation.

A new high-statistic analysis of the semileptonic decay mode of charged kaon to neutral pion, antimuon and muon neutrino $K^+ \to \pi^0 \mu^+ \nu_\mu$ in OKA experiment is presented. The study includes preliminary results of kaon decay form-factor measurements and constraints on the Type-II 2HDM parameters.

The ${}^{238}$U(n,f) reaction plays an important role in modern nuclear energy, so to date many measurements of the cross-section of this process as a function of incident neutron energy have been performed. In most works, the energy interval below 20 MeV, which is most relevant for modern reactor technologies, has been studied. At the same time, the 20–200 MeV region, which will be in demand in future technologies, has been studied somewhat less – see, for example, [1]. In particular, if the uncertainty of the evaluated ${}^{238}$U(n,f) cross-section in the 1–20 MeV region does not exceed 1.5%, then in the 30–50 MeV interval this uncertainty increases to 2–2.5%, and above 100 MeV it exceeds 4% [2].

It is important, however, to understand that experimental data on fission cross-sections can be obtained only for relatively stable isotopes of heavy elements irradiated by neutrons. But in nuclear facilities, short-lived isotopes, which also fission under neutron action, are produced in reactions of the type (n,2n) or (n,p). The fission cross-sections of such isotopes cannot be measured, but they can be estimated using model approaches. At the same time, a method based on such approaches can be developed only by calculating the fission cross-sections of relatively stable isotopes, such as ${}^{238}$U, and comparing the results with measured cross sections.

In this work, the energy dependence of the ${}^{238}$U(n,f) fission cross-section induced by neutrons in the range from 0.1 to 50 MeV has been modeled using the TALYS-2.2 code [3]. At the first stage, the results of calculations performed with default parameters (which, as a rule, are parameters from the RIPL-3 library [4]) were compared with experimental data from the EXFOR library [5]. Discrepancies between the calculated and measured cross-sections were revealed in a number of energy intervals. At the next stage, possibilities for minimizing the discrepancies were studied by adjusting the fission barrier parameters, using alternative approaches for calculating the level density of excited states, as well as for modeling pre-equilibrium processes. As a result, fission barrier and collective enhancement parameters for the nuclei ${}^{239-232}$U were determined, allowing the main features of the measured energy dependence of the ${}^{238}$U(n,f) cross-section to be reproduced. A high sensitivity of the cross-section to the parameters of rotational enhancement of the level density and to the shape of the nucleus at the fission barriers has also been established.

The DANSS experiment at the Kalinin NPP measures the reactor
antineutrino flux and spectrum in order to search for sterile neutrinos
and to address a range of fundamental and applied physics problems.
The readout of the detector's 1 m³ plastic scintillator array is
based on a hybrid system including photomultiplier tubes (PMTs)
and silicon photomultipliers (SiPMs).
High-precision Monte Carlo (MC) simulations, which
are essential for accurate energy reconstruction, require detailed
modeling of the PMT response. This work focuses on the
analysis of the single-photoelectron (SPE) signal characteristics in
these PMTs. To extract these characteristics, the photocathodes were
illuminated with low-intensity LED pulses of varying brightness. The
measured amplitude spectra were approximated using a convolution of a
Poisson distribution — accounting for electron emission statistics from
the photocathode and first dynode — and a Gaussian function representing
electronic noise. By analysis of the dependence of the fit parameters on
light intensity, we derived characteristics for each
individual PMT. The averaged key parameters of the readout system were
determined and successfully implemented into the DANSS MC simulation
framework.

The decoherence curve of muon bundles in extensive air showers is investigated in this work using the FANSY 2.0 package. Using the Monte Carlo method, the development of cascades in the atmosphere is simulated for different types of primary particles (protons and iron nuclei), a wide range of initial energies and zenith angles. The dependence of the spatial distribution of muons at the detector location on the characteristics of the primary cosmic radiation and the shower arrival angle is analyzed. It is shown how variations in the composition, energy, and direction of the primary particle affect the degree of muon-group decoherence and the shape of the distributions. Accounting for muon scattering in the overburden enables comparison of the simulation results with the decoherence curve measured in the LVD experiment (Gran Sasso, Italy). The obtained results allow a refined interpretation of data from underground experiments and an assessment of the sensitivity of the decoherence curve to parameters of the primary cosmic-ray flux.

CENNS-10 is a single phase liquid argon (LAr) scintillation detector deployed by the COHERENT collaboration at the Spallation Neutron Source located at the Oak Ridge National Laboratory in 2017. The detector was designed to study the Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) using the high-quality pion-decay-at-rest neutrino source. The collaboration reported the observation of CEνNS in LAr with CENNS-10 in 2020. After the science run, a series of studies of LAr scintillation properties were performed. LAr as a scintillator produces 128 nm VUV light that lies well outside the reasonable sensitivity region of the most PMTs. Therefore, wavelength shifters (WLS) are commonly used as a solution. CENNS-10 applies tetraphenyl-butadiene (TPB) coating on internal surfaces. It is known that xenon doping to LAr can act as a volume-distributed WLS. To study the scintillation properties of various xenon-argon mixtures a dedicated engineering run was conducted with different xenon concentrations. Current status of the analysis and preliminary results are discussed.

The performance of the Straw Tracker (ST) is one of the key factors determining the momentum resolution of the Spin Physics Detector (SPD) at the NICA collider. The quality of charged-particle track reconstruction depends not only on the detector geometry and event multiplicity but also on the parameters of the track-finding and track-fitting algorithms.

This work focuses on track reconstruction in the SPD ST and its impact on the relative transverse momentum resolution for different charged-track multiplicities. Monte Carlo simulations are used to reconstruct charged-particle trajectories in various light-to-moderate ion-ion collisions. Reconstructed tracks are matched to Monte Carlo “true tracks” via the fraction of common detector hits, which allows one to correctly account for mixed and incorrectly reconstructed track candidates. The transverse momentum resolution is studied using the relative residual, evaluated in different transverse-momentum intervals for different colliding ion species. Wrong hit associations with tracks at high multiplicities result in notable tails in the relative resolution. The choice of an appropriate fit function is also discussed.

The SuperFGD (Super Fine-Grained Detector) is a part of the ND280 near
detector complex for the T2K and Hyper-Kamiokande experiments. The
SuperFGD is a fully active and highly granular scintillator neutrino
detector. It consists of approximately 2 million scintillation cubes,
which allow for the reconstruction of particles traveling in all
directions. A good understanding of the SuperFGD response is crucial
for detailed Monte Carlo simulations and systematics estimation for
further physics analyses. This poster covers the selection of
atmospheric muons stopped inside the sensitive volume of the detector,
including their decays. Muons were selected by applying geometrical
constraints and searching for subsequent electrons or positrons. The
reconstructed spectrum of the Michel e-/e+ is useful as another source
of energy scale determination. Reconstruction of Compton electrons
following positron annihilation allows for the evaluation of the
SuperFGD effective low energy threshold

The reaction of $\pi$ -meson production in proton-proton collision is considered at an energy of 800 MeV. Two reaction mechanisms are taken into account to describe the process. One of them is the one-pion exchange mechanism.
The pion-nucleon interaction is described by an energy-dependent parameterization.

Also, the final state interaction between the two nucleons is included in the consideration. This mechanism is described by the NN wave function, which is obtained by the matrix inversion method. As a result, the reaction amplitude is determined, which allows calculating both the differential cross section and any polarization observables.

This work is devoted to the restoration of the KALIF-8 automated test bench for evaluating the characteristics of photomultiplier tubes of various sizes. During the work, cable lines were replaced, the electronics were updated, and the main components of the measurement system were calibrated. The software for centralized control of the test bench was configured.
During the experimental studies, the main parameters of the reference photomultiplier tube were measured, including gain, linearity range, timing and noise characteristics. To verify the reliability of the results, a comparison was carried out with measurements obtained using an independent test bench. The operability and metrological suitability of the developed system for large-scale calibration of photomultiplier tubes prior to their installation in detectors were demonstrated.

The interest of the scientific community on supernovae (SNe) has increased in the recent years for several reasons. Mostly they are the advances in the understanding of the SN phenomena obtained with the intensive study of nearby SNe, first of all SN 1987A, which have raised new more fundamental questions with regard to progenitor evolution, explosion mechanism and nucleosynthesis.
The Open Supernova Catalog (OSC) is an online dataset contains metadata and observational results for approximately $10^5$ supernovae.The preliminary results of OSC data analysis show that several peculiarities are presented in Ia supernovae redshift distribution. The deviation in the band 0.015 < z < 0.13 contain more faint supernovae. Two peculiarities also were found in the region 0.25 < z < 0.45 on data of this catalogue. One of its contain more faint events, other contain more bright supernovae. Also $faint_m$ and $bright_m$ supernovae areas could be separated by $m_{fb}$ ∼ 20 in distribution of object amount on apparent magnitude. The distribution of SNIa on apparent magnitudes and angular distance to host center also reveal two areas (faintdist and brightdist objects) and ratio between these regions populations is different for different subsamples in OSC (Pan-STARRS1 (PS1) Medium Deep Survey, ASASSN and so on). Also within one host galaxy apparent magnitudes of SNIa could differ for $Δm_{onehost}$ ∼ 2.5 (for example, in UGC03432). Two supernovae SN2016jdv and SN2018qp located in IC988 with redshift $z=0.0269 \pm 0.0002$ at angular distances to host center $\phi_{SN2016jdv}$ = 5.84 and $\phi_{SN2018qp}$ = 7.88 has $Δm_{onehost}$ ∼ 0.4. Moreover, the optical spectra of these supernovae are similar and show no absorption lines that would indicate the absorption of light from a fainter object; thus, the difference $Δm_{onehost}$ ∼ 0.4 for the galaxy IC988 is caused by some other effect.
The observed features and inhomogeneities cannot be explained by the differences between the single-degenerate and double-degenerate explosion scenarios for Type Ia supernovae based on standard nuclear reaction models. Furthermore, the hypotheses regarding a reduction in SN Ia flux due to interaction with the surrounding medium are unsupported by the absence of specific absorption lines in the energy spectra of the analyzed events. Consequently, the presence of such features is likely attributable to variations in the properties of the Metagalaxy at high redshifts or to unknown aspects of Type Ia SN explosion scenarios, leading to sample inhomogeneity. Moreover, the $H_0$ tension effect could be caused due differing ratios of faint to bright SNe Ia within the analyzed subsamples.

Heavy strongly interacting dark matter particles are excluded by data from several experiments (IMP-7/8, XQC, RRS, CRESST, CDMS, and others) within scenarios which assume a velocity-independent nuclear elastic scattering cross section. However, taking into account the location of the detectors avoids some of the constraints if energy loss leads to an increase in such cross section. Scenarios of the thermalization of 2-10 TeV particles were analyzed for several functions $\sigma = \sigma (v)$. The velocity and angular distributions for several penetration depths into the atmosphere and the upper layers of rock were calculated. The results are compared with existing constraints on SIMPs.

Neutron detection is based on the registration of secondary charged particles arising in nuclear reactions with the detector material. The efficiency is determined by the reaction probability and the linear dimensions/material of the detector.
For time-of-flight measurements, fast scintillators or gas detectors are usually used. A promising improvement is to replace part of the passive layers with active layers made of bismuth orthogermanate (Bi₄Ge₃O₁₂, BGO). BGO is characterized by high density ($\rho$ ≈ 7.13 g/cm³), low radiation length (~1.13 cm), radiation resistance, absence of afterglow, and a light yield of ~7000 photons/MeV. The absence of cleavage planes allows the crystals to be shaped into any form. Due to its higher density compared to NaI(Tl) and CsI(Tl) and other popular scintillators, BGO provides higher efficiency in detecting photons and neutrons for the same volume. However, the high density causes partial self-absorption of photons, reducing the signal amplitude, which is compensated for by modern electronics with a high signal-to-noise ratio.
A significant drawback of heavy scintillators is the long rise time of the signal (>100 ns), which makes their use for the time-of-flight method difficult. Nevertheless, the requirements for the neutron detector being developed include the possibility of using the time-of-flight (TOF) method.
This paper demonstrates the fundamental possibility of using BGO for the TOF method.

Majorana neutrino oscillations in a magnetic field are considered using the wave packets formalism. The dispersion relation for neutrinos with non-zero transition magnetic moments propagating in a magnetic field is found in the two flavour case. It is shown that for Majorana neutrinos propagating in a magnetic field the coherence length coincides with the coherence length for neutrino oscillations in vacuum when the vacuum frequency is much greater than the magnetic frequency, while it is proportional to the cube of the average neutrino momentum if. We show that the decoherence effect may appear during neutrino propagation in a magnetic field of supernova.

In recent years, the PHENIX experiment has observed collectivity in small collision systems. This behavior resembles what is seen in large systems where quark-gluon plasma (QGP) is produced. However, whether QGP actually forms in small systems is still being debated.
This work presents measurements of the neutral pion elliptic flow ($v_2$) coefficients as a function of $p_T$ for different centrality classes in p+Au, $^3$He+Au, and p+Al collisions at 200 GeV using the event plane method. In central collisions (0-5%) for $p_T$ from 1 to 3 GeV/c, the $v_2$ values in $^3$He+Au exceed those in p+Au and p+Al. Moreover, in all three collision systems, $v_2$ values rise from central to peripheral collisions, with larger values observed in the 40-60% centrality class.

The directed flow ($v_{1}$) of protons is one of the important observables sensitive to the Equation of State (EoS) of strongly interacting matter produced in relativistic heavy-ion collisions. Detailed differential measurements of protons have been obtained from the analysis of the first physics data of the BM@N experiment for Xe+Cs(I) collisions at a beam energy of 3.8A GeV. Because directed flow depends strongly on the collision geometry, the underlying impact parameter is routinely deduced from experimental data via centrality determination. In this work, we investigate the influence of the centrality determination method on the measurements of the directed flow of protons in the BM@N experiment.

Understanding the properties of strongly interacting matter, particularly the equation of state in the high net-baryon density regime, remains a central goal of relativistic heavy-ion collision physics. Directed flow serves as a powerful probe of the pressure gradients in the evolving system. Light clusters, such as deuterons, are expected to exhibit enhanced sensitivity compared to protons due to their composite nature. Moreover, the production mechanism of light nuclei (e.g., coalescence) and their sensitivity to nucleon dynamics may imprint distinct signatures on the observed flow signals .
In this talk, the results will be reported on the measurement of deuteron directed flow in Xe+Cs(I) collisions at a beam kinetic energy of 3.8A GeV, collected with the BM@N experiment at the Nuclotron/NICA facility. The directed flow will be presented as a function of rapidity in the center-of-mass system, transverse momentum, and collision centrality. The slope of v1 at mid-rapidity is extracted and compared with existing world data from lower and higher energies, including measurements from AGS and STAR.

High-baryonic-density strongly interacting matter is created in collisions of heavy ions, and its properties can be probed through the azimuthal anisotropy of produced particle momenta. This anisotropy is commonly quantified via the Fourier coefficients of the particle azimuthal angle distribution. However, the measured coefficients are susceptible to significant biases introduced by the detector setup. In my talk, I address this challenge by reviewing existing correction techniques and then proposing an upgraded approach based on Principal Component Analysis to account for non-uniformities in the detector azimuthal acceptance. The performance of this new correction is evaluated using high-statistics Monte-Carlo simulations of the BM@N experimental setup, processed through a full chain of data-like reconstruction.

Anisotropic flow is a fundamental observable in relativistic heavy-ion collisions that describes the anisotropy in the azimuthal distribution of emitted particles. It develops mainly due to pressure gradients generated during the early stages of the collision, which transform the spatial anisotropy of the initial overlap region into momentum anisotropy of the final-state particles. In the energy range of NICA complex, due to longer passge time, spectators can strongly influence the observed flow through interactions with emitted particles.
In this work, we study the influence of spectator matter on anisotropic flows in Ag+Ag, Au+Au, Xe+Xe, and U+U collisions at (\sqrt{s_{NN}}=2.4)–4.5 GeV using a modern transport model. Calculations with and without spectator propagation are compared for different particle species, collision energies, and centralities to estimate the spectator contribution to the directed (v1), elliptic (v2), triangular (v3), and quadrangular (v4) flow coefficients.

At the beginning of the 21st century, a new phase of strongly interacting matter,
known as the quark-gluon plasma (QGP), was established [1]. To study QGP formation in
heavy-ion collisions, the solution of system of relativistic hydrodynamics equations with
a specific equation of state (EoS) is typically employed. In light of difficulties for non-zero baryonic potentials within Lattice QCD, various holographic models based on the AdS/CFT duality have been proposed to obtain the QGP EoS from the thermodynamic properties of a corresponding black brane in AdS$_5$ [2].

In this work, we discuss possible phenomenological approach for incorporating not only
the baryon chemical potential but also the quantum numbers of strangeness and charge into holographic thermodynamics. The method proposed employs a phenomenological hypothesis inspired by the thermodynamic dependencies of the hadron gas model. The Thermal FIST [3] package helps us to find the definition for the full chemical potential, which behaves like a hadron gas in the characteristic temperature range. We apply machine learning methods to address regression and optimization problems during the calibration of the model's free parameters using LQCD results for quark masses that approximate the physical values [4]. For practical applications in heavy-ion collision studies, the holographic EoS with strangeness and charge is incorporated into the hydrodynamical packages MUSIC [5] and vHLLE [6].

To obtain final hadronic spectra, numerical simulations were conducted using the iEBE-MUSIC and SMASH-vHLLE frameworks. The various hadronic relations for charged pions, kaons and protons are studied using approach described.

The authors acknowledge Saint-Petersburg State University for a research project ID: 153212394

References

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[2] I. Aref’eva, K. Rannu, P. Slepov, Holographic anisotropic model for light quarks with
confinement-deconfinement phase transition, J. High Energ. Phys. 2021, 90 (2021).

[3] V. Vovchenko, H. Stoecker, Thermal-FIST: A package for heavy-ion collisions and hadronic
equation of state, Comput. Phys. Commun. 244, 295 (2019)

[4] M. Cheng et al., QCD equation of state with almost physical quark masses, Phys. Rev. D 77,
014511 (2008)

[5] B. Schenke, S. Jeon, C. Gale, (3+1)D hydrodynamic simulation of relativistic heavy-ion
collisions, Phys. Rev. C 82, 014903 (2010)

[6] Iu. Karpenko, P. Huovinen, M. Bleicher, A 3+1 dimensional viscous hydrodynamic code for
relativistic heavy ion collisions, Comput. Phys. Commun. 185 (2014), 3016

The MPD experiment will provide particle identification and broad coverage in transverse momentum and rapidity for neutral mesons decaying into photons, using different methodsbased on its electromagnetic calorimeter, tracking, and time-of-flight systems. The spectra and anisotropic flow of neutral mesons may help constrain the properties of the hot and dense nuclear matter created in heavy-ion collisions at NICA collider energies. Moreover, subtracting their contribution from inclusive photon spectra and anisotropic flow is necessary for direct-photon measurements.

We present the performance of inclusive photon, neutral pion, and eta meson spectra and anisotropic flow measurements with the MPD experiment at NICA in both collider (Bi+Bi @ 9.2 GeV) and fixed-target (Xe+W @ 2.87 GeV) regimes. The study was performed using the latest high-statistics simulations with the UrQMD event generator, an updated detector response, and improved reconstruction and analysis procedures, including the rejection of charged particles using the time-of-flight detector and machine-learning-based identification of converted photons.

Anisotropic flow serves as a sensitive probe of the equation of state (EOS) and transport properties of the strongly interacting matter. It is an important observable at intermediate beam energies, which current theoretical models associate with the high baryon density region of the QCD phase diagram. Despite extensive study, this region still requires additional experimental constraints. This work presents a feasibility study of differential anisotropic flow measurements for identified hadrons in the fixed-target mode of the MPD experiment at NICA, which explores the properties of strongly interacting matter at beam energies of 2.3–3.5 GeV. For the first time, results on the higher harmonic anisotropic flow of protons will be shown, specifically their transverse momentum ($p_{T}$) and rapidity ($y$) dependencies. In addition, the large statistics of the analysis enable double-differential $v_{1}$ and $v_{2}$ measurements as functions of $p_{T}$ and $y$, which will also be presented.

We propose a new method for computing approximate solutions of linear evolution equations with slowly varying coefficients. Using this method, we obtain an expansion of the heat kernel. We refer to this expansion as a derivative expansion because each subsequent term contains derivatives of the slowly varying coefficients of a higher order than the previous one does. We also propose a new operator approach for calculating the small-time asymptotic expansion of the heat kernel. It is possible to derive a non-diagonal small-time expansion up to an arbitrary order with this operator method. We explicitly obtain analytical expressions up to the second order in the time variable.

The classicality concept is formulated. It is used to derive Wigner inequalities dependent on three instants. The possibility of testing experimentally violations of these inequalities in pure and mixed flavor states of a pair of neutral pseudoscalar mesons is studied. Within the Werner background model, it is shown that a violation of time-dependentWigner inequalities may be observed even at a 50% fraction of background processes.

The cutting technique for Feynman diagrams is a powerful tool for extracting implications of unitarity. It is widely used and referred to in various areas of quantum field theory, including strong-field QED. However, to the best of our knowledge, no proof of the cutting technique in the presence of a classical background field has been published. In our presentation, we follow M. Veltman's original proof for self-acting scalar field theory and extend it to strong-field QED with a stable vacuum. We also demonstrate the cutting equation on the example of the second-order trident pair creation process and discuss prospects of it's future applications to non-perturbative strong-field QED.

We compute the NMHV form factors of two stress-tensor operators in N=4 SYM at tree and one-loop level using unitarity methods. At tree level, we analyze the general case using the BCFW recursion and identify dual conformal symmetry properties of such form factors. In addition, we calculate the three-point form factors by the CSW recursion and perform a numerical cross-check in Mathematica, finding agreement up to machine precision. At one-loop level, the three-point form factor is expressed in terms of triangle and box integrals. Our results expose dual conformal symmetry properties of such generalized form factors in planar N=4 SYM, which opens up the possibility for all loop analysis using integrability methods.

Monopoles and instantons play crucial roles in understanding quark confinement and chiral symmetry breaking in quantum chromodynamics. However, their relationship remains unclear. In this research, we perform Monte Carlo simulations in lattice gauge theory to identify signatures of monopoles under the influence of magnetic fields, for example, those generated in heavy-ion collision experiments.

In collaboration with a research group at the University of Pisa, we set the parameters for the quark masses to the physical pion mass and generate gauge field configurations with $N_{f}$ = 2 + 1 flavor quarks in SU(3). We apply a uniform external magnetic field to the configurations and vary its intensity.

In our previous study, we reported on the influence of the external magnetic field on monopoles, quark confinement, instantons, chiral symmetry breaking, and the eta-prime meson mass using these configurations.

In this study, we define three contributions — abelian, monopole, and photon — and construct three types of configurations of the gauge fields corresponding to these contributions by subjecting the configurations to Abelian projection after transforming the matrices under the condition of the maximal Abelian gauge. These configurations are prepared for both the quark confinement phase and the quark deconfinement phase.

We then calculate the low-lying eigenvalues and eigenvectors of overlap fermions using the configurations. The overlap fermion represents a quark formulation that preserves the exact chiral symmetry in lattice gauge theory.

Finally, we demonstrate that monopole dominance, that is, the numerical results of observables computed from the configurations of the monopole contribution, reasonably agree with the results computed from the normal configurations, which are not transformed under any gauge condition, even in the presence of external magnetic fields.

In my presentation, I will present the preliminary results.

The QCD phase diagram at high baryon density and moderate temperature is expected to exhibit a rich phase structure beyond the possible first-order transition. Inhomogeneous phases, i. e. phases characterized by spatially modulated condensates, is one of the most intriguing options. These phases, such as the chiral density wave or crystalline condensates are studied as a rule using model calculations, for example, in the framework of Nambu–Jona-Lasinio and quark-meson models. The studies indicate that the inhomogeneous region potentially covers the putative critical endpoint and connects the hadronic and quark-matter phases. Their presence can significantly alter the phase structure and its experimental implications. The status of inhomogeneous phases will be briefly reviewed and new results in quark matter with isospin and chiral imbalance will be discussed. The studies in effective models have their own problems. So the study of low-dimensional models is critical in this context owing to their relative simplicity and renormalizability. The inhomogeneous phases are thoroughly studied in (1+1)-dimensional models. The search for such phases in (2+1)-dimensional models is a recent endeavor, and current evidence suggests they are absent. We check this implication and then discuss (2+1)-dimensional models with one compactified spatial coordinate and study inhomogeneous phases in the crossover regime between these two low-dimensional models and found in what conditions the inhomogeneous phase is realized.

A tensor fermionic current is the part of the Pauli Lagrangian density describing the electromagnetic interaction of fermions through their anomalous magnetic moment (AMM) induced by New Physics. Two-point vector-tensor and tensor-tensor correlators of fermionic currents are calculated in a constant homogeneous electromagnetic field background. Under assumption that this interaction enters the effective QED Lagrangian, the contribution induced by AMM to the photon polarization operator is calculated and its impact is discussed.

We study adjoint Wilson loops in two-dimensional Yang--Mills theory for classical, exceptional, and $\mathfrak{osp}(1|2n)$ Lie (super)algebras. The Wilson loops are evaluated numerically using the Migdal representation-sum formula and compared across different Lie families within Vogel's parametrization. Our main goal is to investigate whether this observable admits a universal description on Vogel's plane, including its large-rank expansion. We find substantial agreement between different series at leading order in the algebra rank and obtain a common Vogel-based continuation that gives a good description of many exceptional-group results. Moreover, the subleading corrections for different series can be jointly parametrized by functions of the Vogel parameters. These results provide evidence for a nontrivial Vogel-universal structure of adjoint Wilson loops, at least in the large-rank limit.

The upgraded near neutrino detector of the T2K experiment is briefly described. The central part is the 3D scintillator fine-grained detector (SuperFGD). The detector comprised of about 2 million 1 × 1 × 1 cm3 plastic scintillator cubes with three orthogonal holes for wavelength shifting fiber readout. It is used as an active neutrino target to detect charged particles and photons. A combination of SuperFGD with the other subdetector systems in the ND280 detector provides a possibility to detect more neutrino events (due to an additional active target), as well as to increase the accuracy of the neutrino events reconstruction.

In charged-current muon-neutrino analysis, the outgoing muon is selected to reconstruct the neutrino energy. In SuperFGD, however, pions can be misidentified as muons, complicating this selection. This work uses a Graph Neural Network (GNN) to identify muons and pions. We present the efficiency and purity of the GNN-based classification of these particles and discuss its impact on event selections. The results are based on Monte Carlo simulations of neutrino interactions in the upgraded ND280 detector.

1. K. Abe et al. (T2K Collaboration), The T2K experiment, Nucl. Instrum. Meth. A 659 (2011) 106-135, DOI: 10.1016/j.nima.2011.06.067

2. Yu. Kudenko et al. (T2K Collaboration), The near neutrino detector of the T2K experiment, Nucl. Instrum. Meth. A 598 (2009) 289-295, DOI: 10.1016/j.nima.2008.08.029

3. Abe S. et al., The super fine-grained detector for the T2K neutrino oscillation experiment. Nucl.Instrum.Meth.A 1092 (2026) 171882

4. Abe K. [et al.]. T2K ND280 Upgrade – Technical Design Report, JINST 6. 2011. P12004 [arXiv:1901.03750 ] Jan. 11 2019, 196 p.

5. Shlomi, J., Battaglia, P., & Vlimant, J.-R. "Graph neural networks in particle physics." Machine Learning: Science and Technology 2.2 (2021): 021001.

Current work aims at the study of heavy neutral leptons, or heavy neutrinos (N), in the mass range $<493 \, \text{MeV}/c^2$ [1]. These particles can be produced in charged pion and kaon decays in the T2K standard neutrino beam: $M^\pm \rightarrow l^\pm_\alpha N$, where ($M=\pi,K; \, \alpha=e,\mu$). Then, heavy neutrinos can decay in ND280 via the following two- and three-body decay modes: $N \rightarrow l^\pm_\alpha \pi^\mp, \, N \rightarrow l^+_\alpha l^-_\beta \nu(\bar{\nu}$), where ($\alpha,\beta = e,\mu$). In order to reduce background from neutrino interactions, we search for heavy neutrino decays in the volume of the Time Projection Chambers (TPCs). The heavy neutrino mass range considered in the current work is wider compared to the previous T2K analysis [2, 3] due to the inclusion of pion decays. Moreover, additional statistics, new Monte Carlo model and updated TPC reconstruction algorithm are used in current analysis. Preliminary constraints on mixing elements between heavy and active neutrinos will be presented.

The work is supported by Russian Science Foundation (RSF) grant № 26-12-00495. Authors are grateful for the assistance given by Y. Kudenko, P. Litchfield and T2K collaboration members.

1. Asaka T. and Shaposhnikov M. "The MSM, dark matter and baryon asymmetry of the Universe". Physics Letters B, 620, 17-26 (2005).
2. Abe K., et al. "Search for heavy neutrinos with the T2K near detector ND280". Physical Review D 100.5 (2019): 052006
3. Antel C., et. al. "Feebly Interacting Particles: FIPs 2022 workshop report". arXiv.2305.01715, pp. 278-281

The T2K experiment uses a high-intensity muon neutrino beam produced at the J-PARC accelerator facility to study neutrino properties and search for physics beyond the Standard Model. Recently, the near detector ND280 was upgraded with a high-performance scintillator detector, the SuperFGD. Composed of approximately 2 million 1 cm³ scintillator cubes read out by wavelength-shifting (WLS) fibers in three dimensions, the SuperFGD enables improved 3D tracking of stopping protons and pions, enhanced electron/photon separation, and neutron detection. This makes the SuperFGD sensitive to feebly interacting exotic particles. In this study, we investigate the potential of the detector to observe millicharged particles (mCPs) with masses up to several GeV, as predicted by various hidden-sector models.

Previous studies have primarily focused on mCP production from neutral unflavoured mesons, while this work extends the production model to include additional hadronic channels. We evaluate the contribution of mCPs generated through charged pion-nucleon scattering and elastic proton-neutron scattering within the target material. These production mechanisms may constitute a non-negligible source of mCPs at T2K energies. Using realistic performance characteristics of the SuperFGD, we estimate the expected signal rates for the topology of double consecutive scatterings of mCPs on atomic electrons. The study will provide an assessment of how pion-nucleon and proton-neutron processes extend the detector's sensitivity in the (mass, millicharge) parameter space.

T2K (Tokai-to-Kamioka) [1] is a long-baseline accelerator experiment aimed at studying neutrino oscillations and searching for CP violation in the lepton sector. Reducing systematic uncertainties in the predicted event rates at the far detector Super-Kamiokande is essential for improving T2K’s sensitivity to the CP-violating phase. The ND280 near detector plays a key role in this task by constraining neutrino flux and interaction model parameters using pre-oscillation data. The time projection chambers (TPCs) [2] provide key information for particle identification (PID) and the reconstruction of charged particle kinematics in ND280. The ND280 upgrade [3] introduced two high-angle TPCs (HA-TPCs), which, together with the three existing vertical TPCs, provide an extended angular acceptance for charged particles.

The TPC PID algorithm [4] is based on measurements of the ionization energy loss of charged particles traversing the TPC gas. The performance of the algorithm and associated systematic uncertainties are evaluated using control samples of muons, protons, and electrons produced in neutrino interactions. The work focuses on the studies of the TPC PID before and after the ND280 upgrade, as well as on the impact of the results and evaluated systematics on muon-candidate selection using the ND280 near detector data. This work is supported by Russian Science Foundation grant No. 26-72-00042.

[1] K. Abe et al. (T2K Collab.). Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations, Nature 580 (2020) 339–344. 

[2] N. Abgrall et al. (T2K ND280 TPC Collab.). Time Projection Chambers for the T2K Near Detectors, Nucl. Instrum. Meth. A 637 (2011) 25–46.

[3] K. Abe et al. (T2K Collab.). T2K ND280 Upgrade — Technical Design Report, arXiv:1901.03750 [physics.ins-det] (2019).

[4] A. Dergacheva and A. Izmaylov. Evaluation of uncertainties associated with particle identification in the time projection chambers of the ND280 near detector of the T2K experiment, Physics of Atomic Nuclei 89, 4 (2026).

The Tokai-to-Kamioka (T2K) experiment is a long-baseline neutrino oscillation experiment in Japan. T2K is designed to precisely measure neutrino oscillation parameters and search for CP violation in the lepton sector using an intense muon (anti)neutrino beam. Measurements with the near detector, ND280, are essential for constraining neutrino interaction models and the initial neutrino flux, thereby reducing systematic uncertainties in the oscillation analysis. In 2024, ND280 was upgraded with the novel 3D-segmented SuperFGD detector at its core. This work presents the first analysis of muon neutrino interactions in the SuperFGD detector. The results establish the foundation for incorporating the upgraded ND280 into the T2K oscillation analysis, improving its overall precision and laying the groundwork for the next-generation Hyper-Kamiokande experiment at the J-PARC beamline.

The accuracy of extracted neutrino oscillation parameters in accelerator-based neutrino experiments depends on the precision of neutrino-nucleus scattering models implemented in neutrino event generators. The goal of this study is to asses the accuracy of the GENIE event generator with electron scattering data. To do this we carry out a comparison of the charged-current quasielastic CCQE reduced cross sections of the semi-exclusive (l,l'p) lepton scattering process calculated within the models employed in the GENIE event generator with data measured in electron scattering on oxygen targets. This comparison is based on the similarity of the reduced cross sections of neutrino and electron scattering up to Coulomb corrections. Irrespective of the type of interaction the reduced cross section identified with distorted nuclear spectral functions is determined mainly by intrinsic properties of the target and the ejected nucleon interaction with residual nucleus. This study includes GENIE's main models and Tokyo, NIKHEF electron data sets in energy range 0.3 GeV - 0.5 GeV. Persistent disagreements between the GENIE predictions and electron scattering data for reduced cross sections is observed.

An analysis of available experimental and observational data as well as some theoretical assumptions related to the masses and mixing angles and mixing phases of active and sterile neutrinos was conducted. Based on these experimental and theoretical results and the analysis, estimates of the masses and mixing parameters of active and sterile neutrinos were obtained. These estimates can be used in calculating the characteristics of neutrino processes.
At transition to models generalizing the Standard Model (especially with sterile neutrinos [1, 2]) the theory will depend on new constants, which will be in relations with the SM constants. The presence of such relations will indicate possible paths for further development of the theory [3]. Moreover the estimates of the masses and mixing parameters presented in this paper may have practical significance for the interpretation of neutrino experimental data.
1. V.V. Khruschov, S.V. Fomichev, O.A. Titov, Physics of Atomic Nuclei 79, 708 (2016).
2. A V . Yudin D K . Nadyozhin, V.V. Khruschov, S.V. Fomichev, Astron. Lett. 42, 800 (2016).
3. A.V. Borisov and A.P. Isaev, Phys. Part. Nuclei 55, 634 (2024).

Об оценках значений масс и параметров смешивания активных и стерильных нейтрино
Проведѐн анализ имеющихся экспериментальных результатов и наблюдательных данных, а также некоторых теоретических предположений, относящихся к значениям масс, углов и фаз смешивания активных и стерильных нейтрино. На основе экспериментальных и теоретических результатов с учетом проведенного анализа получены оценки значений масс и параметров смешивания активных и стерильных нейтрино. Эти оценки могут быть использованы при вычислениях характеристик нейтринных процессов.
При переходе к моделям, обобщающим Стандартную модель (особенно со стерильными нейтрино [1, 2]), теория будет зависеть от новых констант, которые будут связаны с константами СМ. Присутствие таких соотношений будет указывать возможные пути дальнейшего развития теории [3]. Более того, оценки масс и параметров смешивания, приведенные в этой работе, могут иметь практическое значение для интерпретации нейтринных экспериментальных данных.

Rapid technological advances pave the way for high-precision experiments, particularly in neutrino physics. Such enhanced precision offers new opportunities to search for new physics — physics beyond the Standard Model (BSM). In this context, neutrino scattering on matter is of particular interest, as it incorporates information regarding both the neutrino itself and the target matter.

From this perspective, deep inelastic neutrino scattering possesses a number of key advantages. The interest in neutrino scattering specifically stems from recent scientific discoveries indicating that neutrinos should have electromagnetic properties, which, in turn, explicitly point to BSM physics. However, at this level of precision, electroweak radiative corrections must also be taken into account.
The present study is devoted to the theoretical analysis of high-energy neutrino-matter scattering processes, taking into account the electromagnetic and weak properties of neutrinos alongside one-loop contributions, as well as to evaluating their impact on the interpretation of experimental data.

Within the framework of quantum field theory, one-loop electroweak radiative corrections to the neutrino-matter scattering cross-section formula were calculated, incorporating the electromagnetic properties of neutrinos via the theoretical formalism of the form-factor decomposition of the vertex function. In addition, the parameterization of neutrino form factors modifying neutral currents was performed. Finally, it is demonstrated how these effects alter the differential scattering cross sections with respect to momentum transfer.

Measurements of difference between vector and axial form factors $F_V-F_A$ in the decay $K^+\to\mu^+\nu\gamma$. Data acquired in 2012 and 2018 is used in the analysis. measurement using latter dataset is presented for the first time.

The high statistics search for structure dependent (SD) components of radiation in K+ -> e+ nu pi0 gamma decay is performed by the OKA collaboration. The 4-dimensional distribution of about 3000 events of the decay in the phase space area of E(gamma)>30 MeV, Theta(e-gamma)<20 degrees analysed. The total SD contribution to branching ratio (including interference) is measured to (3 +- 5.4)x10^-6.
As the measurement errors don't allow to claim the observation, we set the 90% CL upper limit of 10^-5. This is in agreement with the Chiral Perturbation Theory (ChPT) predictions and is 5 times lower than the current PDG limit.
For the first time the chiral axial anomaly (AA) contribution is measured separately to (0+-2.3)x10^-6, < 3x10^-6 90% CL.

Recent results on searches for rare and forbidden decays at the CMS experiment at the LHC are presented. The analyses use data collected in proton-proton collisions at center-of-mass energies of 13 and 13.6 TeV.

The connection between Standard Model (SM) particles and light dark matter (LDM) can be introduced via spin-0, spin-1, and spin-2 mediators. Moreover, in a mediator mass range from sub-MeV to sub-GeV, fixed-target facilities can potentially probe such particles of the hidden sector via missing energy signatures that are described by the bremsstrahlung-like process involving leptons. We also discuss current and prospect experimental reaches for hidden mediators of LDM, axion-like, and millicharged particles in the light of regarding fixed-target experiments.

The latest results on the search for light dark matter in the NA64 experiment are presented. Searches in electron, muon, and hadron beams are considered. The plans for modernization of the installation for operation in high-intensity beams are outlined.

In the talk I'll discuss the physics program for searching for new physics in the experiment of the recently proposed TiMoFey project, based at the Troitsk Meson Factory of the Institute for Nuclear Research of the Russian Academy of Sciences. The project involves the use of a high-intensity proton beam with an energy of 423 (1300) MeV during its first (second) stage. The project's capabilities for detecting signals from new light long-lived particles produced in collisions between the proton beam and the target will be discussed.

Recently [Phys. Rev. D 112 (2025) 035003; arXiv:2506.18595 [hep-ph]], we proposed an experimental project called the Cosmological Axion Sarov Haloscope (CASH), aimed at searching for dark-matter axions via their conversion into microwave photons in a magnetic field. The key feature of the experiment is the use of Josephson-junction single-photon detectors (JJ SPDs) operating at ultralow temperatures, where thermal noise is negligibly small. This allows us to probe the axion–photon coupling with ultrahigh precision, with sensitivity to gaγγ∼(10^{−14}–10^{−15}) GeV^{−1} for axion masses in the range 38–54 μeV, motivated by generic QCD axion models.

In this talk, we also describe the current preparation for the launch of the first stage of the experiment: measurements of the parameters of fabricated JJ SPDs and a high-quality-factor cavity. In addition, we discuss the design features of tunable cavities and existing prototypes.

A review and status of neutrino experiments measuring the fundamental properties of neutrinos will be presented. This will include oscillation results from both long and short baseline accelerator based programs. In addition, experiments designed to explore the absolute mass of neutrinos and if they are either Dirac or Majorana fermions will also be reviewed. An emphasis will be placed on recent results from running experiments. Finally the status plus plans of future experiments will also be discussed.

The primary goal of the Jiangmen Underground Neutrino Observatory (JUNO) is to determine the neutrino mass ordering (NMO) by measuring the fine structure of the reactor antineutrino oscillation spectrum, and to precisely measure the neutrino oscillation parameters, including $\sin^2 \theta_{12}$, $\Delta m_{21}^2$, and $\Delta m_{31}^2$.
Located in Guangdong, China, approximately 700 m underground and a baseline of 53 km from the reactor cores, the JUNO central detector consists of a 20 kton liquid scintillator target and a dual-calorimetry system based on two independent photodetection systems.
After over a decade of construction and commissioning, JUNO began physics data taking on August 26, 2025. Using only the first 59.1 days of data, the experiment has already delivered world-leading measurements of $\sin^2 \theta_{12}$ and $\Delta m_{21}^2$. This talk will present the overall detector performance of JUNO and its latest physics results.

Reactors are powerful sources of antineutrinos in the energy range of a few MeV,
producing about 2*10^20 antineutrinos per second per 1 GW of the thermal power. A lot of interesting studies at the forefront of modern physics can be carried out
with a detector placed in a vicinity of the reactor core. These studies include searches for the physics beyond the Standard model like sterile neutrinos, large extra dimensions, neutrino magnetic moment and millicharge. The talk will review new results in this area as well as coherent elastic neutrino-nucleus scattering, reactor monitoring using its antineutrino flux and the high energy tail of the neutrino spectrum.

In this talk, we present an overview of hot and dense matter study in heavy ion collisions from STAR experiment at Relativistic Heavy Ion Collider, which include recent highlights in QCD phase transition, critical point search, heavy flavor & jet, electromagnetic probe, global polarization in heavy ion collisions. The nucleon spin structure study with proton-proton collision will also be discussed.

The selection of new results of the LHC experiments on heavy-ion physics at the LHC will be presented.

High Intensity Heavy-ion Accelerator Facility (HIAF) is one of China's major scientific and technological infrastructure projects and one of the world's largest ion accelerators capable of accelerating all ions. HIAF is designed to deliver the intense pulsed heavy-ion beams, comprises a superconducting ion linear accelerator, a high-energy synchrotron booster, a high-energy radioactive isotope beam line, a spectrometer ring, and several advanced experimental platforms. After seven years of construction, HIAF completed its first oxygen beam commissioning in October 2025 and first bismuth beam commissioning in December 2025. HIAF features unprecedented intense ion beams from hydrogen through uranium, by which a large variety of exotic nuclear matters not existing on Earth can be produced, including super-heavy nuclides, short-lived extremely neutron-rich and proton-rich nuclides, finite nuclear matters in the Quantum Chromodynamics phase diagram, exotic nuclides containing hyperons and other hadrons, meson-nucleus bound systems, and highly-charged ions. Therefore, HIAF will be one of the world’s leading heavy-ion accelerator complexes in the envisaged future. As a scientific user facility, researchers from all over the world can approach the experimental limits and open new domains of physics research.

The study of the spin effects and polarization phenomena in hadronic reactions requires the development of high intensity polarized beams, polarized targets, beam and focal polarimetry, systems of the spin manipulation and control as for the current spin experiments at the fixed targets as well as for the planned SPD experiment in collider mode at the Nuclotron/NICA complex.
The main goals of the SPRINT@NICA project is to provide the spin transparency regime for polarized protons and deuterons over whole energy range of Nuclotron and NICA, further development of the Source of Polarized Ions with corresponding deuteron and proton beam polarimeters, development of the polarized 3He target and beam. The extension of the spin program to the search of axion-like particles, measurement of the EDM with beams of polarized protons and deuterons is planned. First line experiments on the deteron and proton spin manipulation are discussed.

We present cosmic muon flux measurements performed across two geomagnetically distinct environments with a novel concentric double-layer plastic scintillator telescope, developed and produced entirely in-house. The detector employs a nested geometry in which a cylindrical active core is coaxially enclosed by a cup-shaped outer scintillator, so that coincidence between the two optically isolated volumes provides active background rejection and wide-angle acceptance within a portable, two-channel package. Both volumes were cast from a custom epoxy-resin matrix doped with PPO and POPOP, a liquid-phase route that removes the need for geometry-specific glass moulds and permits complex shapes such as the outer cup, which would be difficult and costly to machine from commercial scintillator blocks. GEANT4 simulations give a geometric factor of 60.6 cm²sr, in agreement with the Sullivan analytical prediction to within 2% and approximately three times that of a conventional flat two-panel telescope built from the same detector diameters. The nested geometry exhibits no hard angular cut-off, and its coincidence efficiency is flat from 50 MeV to 50 GeV, so that soft muons below 1 GeV/c are registered without loss.

The system was deployed during the 10th Turkish Antarctic Expedition, with measurements taken at a mid-latitude baseline in Istanbul and at Horseshoe Island, Antarctica. After barometric correction the Antarctic flux exceeds the Istanbul baseline by approximately 41%, consistent with the reduced geomagnetic cut-off rigidity at polar latitudes and with an appreciable soft-component response, the latter independently supported by a barometric coefficient ratio of about 3.3 between the two sites. A Forbush decrease was also recorded in Istanbul, coinciding with a Kp ≈ 8 geomagnetic storm driven by a coronal mass ejection and corroborated by simultaneous neutron monitor data. Pre- and post-expedition fluxes agree within statistical uncertainty, indicating that intercontinental transport did not affect the detector response.

The talk additionally reports on the wider scintillator development programme from which this instrument emerged: the optical and scintillation characterisation of the epoxy-resin material against commercial scintillators, laboratory results on formulations engineered for pulse-shape discrimination including lithium-tetraborate nanoparticle loading for thermal-neutron sensitivity, and a Monte Carlo feasibility study of opaque plastic scintillators for muon tomography.

The neutron instrument complex "Neutron Beta Decay" is currently being manufactured to be located on the beam of polarized cold neutrons on the GEK-3 N0 channel. The facility is designed to measure the electron, neutrino, and electron-neutrino asymmetries of neutron beta decay. The experiment is necessary because the results of the most recent, most precise neutron decay experiments, conducted at an accuracy level of 10$^{−3}$, cannot be described within the Standard Model. The basis of the facility is a superconducting solenoid, which generates a uniform magnetic field of 0.35 T. Electrons and protons produced during neutron decay move in a magnetic field along magnetic field lines. To select a specific electron emission angle, a magnetic mirror effect is used by creating a region with a stronger magnetic field, with an induction of 0.88 T. The decay region is selected by protons, which are further accelerated by an electric field. This is achieved by using an electrostatic system that increases the voltage in the decay region to 30 kV. Detectors at the input and output of the neutron beam are used to record the electrons and protons. The aim of the experiment is to improve the accuracy of measuring correlation coefficients by ~3 times. Comprehensive simulation of the experiment was carried out.

New ultracold neutron source based on superfluid helium is being constructing at the PIK reactor for researches in the field of fundamental interactions physics. The use of superfluid helium will allow achieving an UCN density in the source chamber of 3400 cm-3, which is an order of magnitude higher than the current UCN density in sources around the world.
To create this UCN source some important technologies has been developed and implemented: obtaining and maintaining superfluid helium at low temperatures under conditions of heat influx from the reactor, manufacturing neutron guides with a high UCN reflection coefficient, developing heat exchangers for ultra-low temperatures and obtaining isotopically pure helium-4.
The UCN source neutron guide system is designed for four scientific stations. During the first stage of the source's operation, it is planned to install an EDM spectrometer with a measurement sensitivity of 1E-27 e∙cm/year and two experiments to measure the neutron lifetime with an accuracy of 0.1 seconds using gravitational and magnetic traps.

The fundamental process of coherent elastic neutrino-nucleus scattering (CEvNS) has been predicted based on the Standard Model of elementary particles and interactions more than 40 years ago. For heavy nuclei, the cross-section of this process exceeds (in more than two orders of magnitude) the cross-sections of other known low-energy neutrino interaction processes such as inverse beta decay and neutrino scattering off atomic shell electrons. This interaction channel plays a significant role in Universe processes accompanied by intensive neutrino fluxes and can be used to monitor the state of nuclear reactor cores enhancing nuclear power safety. The CEvNS process was first detected in an accelerator experiment in 2017 by the international COHERENT collaboration, in whose work some of the authors of this project participate. Detecting the CEvNS process for reactor neutrinos is a significantly more challenging task, as the energy release from elastic coherent scattering off heavy atomic nuclei does not exceed a few hundred eV. At the Inter-departmental Laboratory for Experimental Nuclear Physics of NRNU MEPhI the RED-100 cryogenic two-phase emission detector has been developed and constructed to study the CEvNS process for reactor electron antineutrinos. The detector is based on a technology first proposed at MEPhI approximately 50 years ago and currently used worldwide in experiments searching for dark matter particles in the Universe.
In 2020–2022 the RED-100 detector, utilizing ~200 kg of liquid xenon as working medium, underwent testing at the Kalinin Nuclear Power Plant. The experiment demonstrated that the reactor neutrino detection technology developed at NRNU MEPhI is capable of detecting the CEvNS effect in a nuclear power plant environment. This study provided the best current upper limit on the CEvNS cross-section for xenon nuclei, which is consistent with the Standard Model. Preparatory work has since been carried out for an experiment using a modified version of the RED-100 detector aimed at detecting reactor neutrinos via the CEvNS interactions with argon nuclei serving as the neutrino target.
An analysis of the results from the first experiment using liquid xenon as the working medium of the RED-100 (2020–2022), combined with laboratory tests of the RED-100 using liquid argon (2025–2026), has shown that using argon atoms as a target for reactor neutrinos will enable reliable observation of the CEvNS effect. To verify this conclusion, it is proposed to conduct the second test of the RED-100 setup with liquid argon working medium at the Kalinin NPP. This project aims to develop independent methods for the remote monitoring of the active core of NPP reactors.

The Multi-Purpose Detector (MPD) at NICA is primarily designed for collider experiments at $\sqrt{s_{NN}} = 4–11$ GeV. A recently proposed program of fixed-target experiments extends its research potential, allowing for the investigation of dense baryonic matter in ion collisions at lower center-of-mass energies $\sqrt{s_{NN}} = 2.4–3.5$ GeV. Running in the fixed-target mode requires a careful revision of the MPD efficiency for event triggering, as well as its performance in particle reconstruction and identification, momentum resolution and geometric acceptance.

In this report, we present a review of the physics performance of the MPD operating in the fixed-target mode, including the results of physics feasibility studies for measuring a wide range of physics observables in Xe+W collisions at $\sqrt{s_{NN}} = 2.87$ GeV. The reconstruction of identified charged and neutral light hadrons, strange mesons and baryons, short-lived resonances, and light nuclei is discussed. The obtained results demonstrate that the MPD in the fixed-target configuration preserves sufficient trigger efficiency and geometrical acceptance, offering a powerful means to advance our understanding of the QCD phase diagram at high net-baryon density.

Due to quantum statistical effects and final-state interactions, momentum correlations between two or more particles emitted with small relative velocities (or, equivalently, small relative momenta in their center-of-mass system) provide a sensitive tool for probing the spatiotemporal characteristics of particle-production processes at femtometer scales (10^−15 m). Kaons are particularly valuable for studying Bose–Einstein correlations because they are less affected by resonance decays than more abundantly produced pions and, therefore, provide a more direct probe of the properties of the primary particle-emitting source created in high-energy collisions. Combined with femtoscopic measurements of pions and protons, kaon correlations also offer important information about the collective dynamics and evolution of strongly interacting matter. We report on the results of the femtoscopic analysis of Bose–Einstein correlations of charged kaons in p–⁠Pb and Pb–Pb collisions at √sNN = 5.02 TeV with the ALICE detector. Both measurements show that the extracted source radii increase with charged-particle multiplicity and decrease with increasing pair transverse momentum. This behavior is characteristic of space–momentum correlations associated with collective expansion and can be described within hydrodynamic models. The time of maximum kaon emission is determined through a three-dimensional femtoscopic analysis for both collision systems. The value obtained in p-Pb collisions is comparable to that observed in highly peripheral Pb–Pb collisions, suggesting that the evolution of kaon emission is similar in p–Pb and peripheral Pb–Pb collisions. The EPOS-3 hadronic interaction model reproduces the measured source sizes in p–Pb collisions reasonably well, except for an underestimation of the source size in the most central collisions. For the Pb–Pb data, the integrated hydrokinetic model provides a good description of the transverse-momentum dependence of the source radii, except for the outward component in the longitudinally comoving system (LCMS).

Femtoscopic correlations of identical particles provide a powerful tool for probing the space-time structure and dynamical evolution of the particle-emitting source created in relativistic heavy-ion collisions. Measurements of femtoscopic radii constrain the characteristic homogeneity lengths of the expanding system and their dependence on collision geometry and particle momentum, thereby providing sensitivity to collective expansion and freeze-out dynamics. The intermediate collision-energy region is particularly important, as it bridges the high-energy, low-baryon-density regime and the baryon-rich matter produced at lower energies, offering an opportunity to study how the space-time evolution of the system changes with collision energy. Comparing different particle species, in particular pions and kaons, provides additional constraints because of their different masses, production mechanisms, and contributions from resonance decays.

We present a systematic femtoscopic study of identical charged pion and kaon pairs in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=14.6$ and $19.6$ GeV simulated with the EPOS4 model. Three-dimensional two-particle correlation functions are constructed in the Bertsch–Pratt decomposition of the relative momentum into the out, side, and long components. The femtoscopic parameters are extracted as functions of collision centrality and pair transverse momentum, $k_{\mathrm{T}}$, for both pion and kaon pairs. The centrality and $k_{\mathrm{T}}$ dependences of the extracted $R_{\mathrm{out}}$, $R_{\mathrm{side}}$, and $R_{\mathrm{long}}$ radii are compared between pions and kaons and between the two collision energies. These results characterize the space-time structure and momentum dependence of particle emission predicted by EPOS4 in the intermediate-energy regime and provide a baseline for comparisons with experimental femtoscopic measurements.

A.Zarchikov, G.A.Feofilov*

     Saint-Petersburg University, St. Petersburg State University, SPbSU,
    SPbU, 7/9 Universitetskaya nab., St. Petersburg, 199034 Russia.
    *e-mail: g.feofilov@spbsu.ru

High-order cumulants of event-by-event multiplicity distributions are widely used in the search for the QCD critical point in relativistic heavy-ion collisions. Their sensitivity to non-Gaussian fluctuations [1] makes them promising observables [2], but at the same time they can be strongly affected by non-critical background effects, in particular by volume fluctuations and by the procedure of centrality class selection[3].

In this work, we study these effects using a simple toy Monte Carlo model of nucleus-nucleus collisions. The collision geometry is described through the impact parameter and the corresponding number of participant nucleons. Particle multiplicity is generated as a superposition of elementary nucleon-nucleon sources. In the first version of the model, the elementary source is assumed to be Gaussian. We show that even in this case nonzero third- and fourth-order cumulants can appear after selecting events by final-state multiplicity, due to the admixture of events with different collision geometry and different effective volume.

The model is then extended to the inclusion of non-Gaussian elementary sources. This allows us to compare two different contributions to high-order cumulants: the intrinsic non-Gaussianity of particle production -- in case of proximity to the critical point, and trivial contribution caused by the volume fluctuations. Special attention is paid to the comparison of multiplicity-based event -by-event selection of narrow classes of participating nucleons (Npart).

The results demonstrate that the measured values of high-order cumulants may be significantly distorted by centrality and volume fluctuations even in the absence of critical dynamics. Therefore, careful control of the initial geometry and the use of narrow classes of the number of Npart and relevant reduced cumulants are essential for separating possible critical-point signals from the non-critical background contributions.

The authors acknowledge Saint-Petersburg State University for a research project ID: 153212394

References:
[1]. M. A. Stephanov, Phys. Rev. Lett. 102, 032301 (2009).

[2]. Hannah Elfner and Berndt Müller 2023, J. Phys. G: Nucl. Part. Phys. 50 103001.

[3]. G.Feofilov, Phys.Part and Nucl., 2026, vol.57, No.3, pp 401-406.

Higher-order multiplicity fluctuations can reveal features of particle production that are not accessible through variances and two-particle correlations alone. Their interpretation, however, is complicated by fluctuations in the number of particle-emitting sources. We develop a systematic construction of strongly intensive observables that remove this dependence within the independent-source model.

Starting from the relations between the joint cumulants of observed multiplicities, the emission properties of a single source, and the source-number distribution, we construct independent combinations at successive orders. We discuss their normalization relative to independent particle production, extending the approach used for the second-order quantities Sigma and Delta. Particular attention is paid to the fourth-order observable Upsilon and its relation to other independent combinations at the same order. The study establishes the conditions under which source-number fluctuations cancel and explores the additional information carried by higher-order strongly intensive observables.

The authors acknowledge Saint-Petersburg State University for a research project ID: 153212394

In heavy-ion collision, the global collectivity of final-state particles can be quantified by anisotropic flow coefficients ($v_n$). These coefficients carry information about the initial geometry of the system, the equation of state, and the expansion dynamics of strongly interacting matter. While $v_n$ studies have mainly focused on the large collision systems at the energies relevant to the NICA program ($\sqrt{s_{NN}}$ = 4.5-11 GeV), light and intermediate-size systems remain largely unexplored in this energy domain. O+O collisions at low energies represent an intermediate-size system, needed to establish system-size dependence of $v_n$ at high baryon density.

In this work, O+O collisions at $\sqrt{s_{NN}}$ = 6 GeV are simulated using the UrQMD model to study the directed, elliptic and triangular flow of charged hadrons, which may help to establish the limits of hydrodynamic-like behavior as a function of system size, and serve as a reference for future experimental studies at NICA.

Study of the strange particle production in nuclear collisions is one
of the most important items of the physics program of the BM@N and MPD
experiments at the NICA complex.

The BM@N Collaboration currently analyzes experimental data obtained
in interactions of Xe beam with CsI and Sn targets at different energies.
At the same time, recent MPD experiment simulations showed its ability to
run in the fixed-target mode at similar energies as BM@N. Some results of
both experiments on strangeness production study will be presented.

The Multi-Purpose Detector (MPD) at the NICA facility is designed to study heavy-ion collisions at $\sqrt{s_{NN}}$ = 4-11 GeV, providing access to the baryon-rich region of the QCD phase diagram. Measurements of strange particles and hyperons are important for studying particle production mechanisms and the properties of strongly interacting matter at high baryon density. In particular, the $\Sigma^{0}$ hyperon, reconstructed through its electromagnetic decay $\Sigma^{0} \rightarrow \gamma\Lambda$, provides a possibility to study hyperon production as well as the reconstruction of low-energy photons in the MPD experiment.

We present a feasibility study of $\Sigma^{0}$ reconstruction in Bi+Bi collisions at $\sqrt{s_{NN}}$ = 9.2 GeV using full MPD detector simulations. $\Lambda$ candidates are reconstructed through the $\Lambda \rightarrow p\pi^{-}$ decay channel, while photons are reconstructed using both the Photon Conversion Method (PCM) and the Electromagnetic Calorimeter (ECal). The reconstruction techniques and performance using PCM and ECal photons are discussed and compared. The results demonstrate the current performance of $\Sigma^{0}$ reconstruction in MPD, providing a basis for further optimization and future experimental data analysis.

The development of a Highly Granular Time-of-Flight Neutron Detector (HGND) for measuring neutron yields and flow in the 0.3-4 GeV kinetic energy range in nuclear collisions at the BM@N experiment is almost finished. To validate the concept of the full-scale HGND, a compact HGND prototype was tested in 3.8A GeV 124Xe collisions with a CsI target in the BM@N experiment in 2022. The prototype was positioned at an angle of 0 degrees to the undeflected beam axis in order to measure the yields of spectator neutrons resulting from hadronic interactions of nuclei, as well as the yields of neutrons resulting from electromagnetic dissociation (EMD) of projectile nuclei [2].

Despite the high neutron detection efficiency and relatively good time resolution of the HGND prototype of approximately 270 ps, it is insufficient for measuring high-energy neutrons. The measured neutron kinetic energy spectra, reconstructed using the time-of-flight method, are significantly smeared due to the contribution of the time resolution. In order to restore the true neutron kinetic energy spectrum from the distorted reconstructed spectrum, an unfolding procedure was used [3]. This method of spectrum reconstruction uses the measured kinetic energy spectrum as input data, as well as the detector response matrix and background estimations obtained through the detector response simulation in the complete geometry of the BM@N setup using the DCM-QGSM-SMM and UrQMD-AMC models as event generators. An intercomparison of the various unfolding methods implemented in the RooUnfold framework for reconstructing the neutron spectrum was conducted.

This approach allows the measurement of double-differential inclusive cross sections of forward neutron emission as a function of rapidity and solid angle even with limited time resolution. In order to validate the approach, measurements of neutrons from EMD were performed, as these neutrons are characterised by a very narrow energy distribution, centred around the projectile beam energy [4].

References

1. S. Morozov et al., Nucl. Instrum. Meth. A 1072, 170152 (2025).
2. A. Zubankov et al., Nucl. Sci. Tech. 36, 226 (2025).
3. L. Brenner et al., Int. J. Mod. Phys. A, 35 (24), 2050145 (2020).
4. I.A. Pshenichnov et al., Int. J. Mod. Phys. E 33, 2441007 (2024).

The Baryonic Matter at Nuclotron (BM@N) is a fixed-target experiment (JINR, Dubna) aimed at studying heavy ion collisions at beam energies up to 4 A GeV. To extend its capabilities, the Highly Granular Neutron Detector (HGND) [1] has been developed. This detector will enable unique measurements of neutrons in the kinetic energy range of 0.3–4.0 GeV. These measurements will make it possible to explore the isospin term of the equation of state (EOS) of baryonic matter. The HGND comprises two arms, each consisting of 8 layers of plastic scintillator with copper absorber plates in between. Each scintillation layer is assembled from an 11×11 matrix of individual cells, providing high spatial granularity and a time resolution of ~150 ps.

As an observable sensitive to the isospin-dependent term of the EOS, the ratio of neutron and proton spectra was proposed [2]. To determine the experimental sensitivity, Monte Carlo simulations of Xe+Cs collisions were performed. The simulations were done using the SMASH [3] model at a beam kinetic energy of 2.5 A GeV. A set of isospin symmetry potentials was used to study the difference in the spectra. The proton spectrum reconstruction procedure is already developed [4]. In this work, the neutron spectrum reconstruction procedure from HGND data is discussed. Special attention is paid to the neutron spectrum reconstruction using a plastic absorber for background removal.

References:
1. S. Morozov et al., Nucl. Instrum. Meth. A 1072, 170152 (2025)
2. Bao-An Li, C. M. Ko, Zhong-zhou Ren, Phys. Rev. Lett. 78 (1997), 1644
3. https://github.com/smash-transport/smash
4. BM@N Collaboration • S. Afanasiev (Dubna, JINR) et al., JHEP 08 (2025), 095

    The difference between the numbers of neutrons and protons in atomic nuclei defines the isospin asymmetry of nuclei. The squared relative difference between the local densities of neutrons and protons contributes to the density-dependent symmetry energy term in the equation of state of nuclear matter. In particular, this contribution makes the nuclei with a large neutron excess unstable and defines the parameters of neutron stars [1]. Comparative studies of nuclear reactions induced by projectiles with similar mass numbers but differing neutron and proton numbers on the same target allow for systematic investigations of isospin asymmetry effects [2]. As found in Ref. [2], the cross sections for the production of heavy isotopes are particularly sensitive to the isospin content of projectile nuclei.

    In this work, the Abrasion-Ablation Monte Carlo for Colliders model with pre-equilibrium clustering based on the Minimum Spanning Tree algorithm (AAMCC-MST) [3,4] was used to study the production of light spectator fragments. In AAMCC-MST, the Glauber Monte Carlo model [5] is used to calculate the numbers of participant and spectator nucleons. The latter are assumed to form spectator prefragments. In particular, in peripheral collisions such prefragments consist of multiple excited nuclear clusters defined by the MST clustering algorithm [3]. Depending on their excitation energy, the clusters undergo various secondary decays simulated with de-excitation models from the Geant4 library [6].

    Fragmentation of relativistic nuclei can be investigated using forward detectors in the Baryonic Matter at Nuclotron (BM@N) experiment [7] at the NICA accelerator complex. Specifically, light spectator fragments with charges Z = 1–5 from the fragmentation of 3.8A GeV $^{124}$Xe on a CsI target can be measured by the scintillation wall [8]. The potential use of a $^{136}$Xe beam is currently under discussion. Here, we present a comparative study of light spectator fragment emission in collisions of $^{124}$Xe and $^{136}$Xe with $^{130}$Xe representing the CsI target. Production cross sections for fragments with Z = 1–5 were calculated as a function of collision centrality. In addition, the relative yields of spectator protons, $^{2,3}$H, and $^{3,4}$He in the 10 % of most central collisions were calculated to probe the isospin content of the fragmenting systems.

References

1. Steiner A. W., Prakash M., Lattimer J. M., Ellis P. J. Isospin asymmetry in nuclei and neutron stars // Phys. Rep. 2005. Vol. 411. P. 325.
2. D. Henzlova, K.-H. Shmidt, M.V. Richardi et al, Experimental investigation of the residues produced in the 136Xe + Pb and 124Xe + Pb fragmentation reactions at 1A GeV // Phys. Rev. C 2008. Vol. 78. P. 044616.
3. Nepeivoda R., Svetlichnyi A., Kozyrev N., et al. Pre-Equilibrium Clustering in Production of Spectator Fragments in Collisions of Relativistic Nuclei // Particles. 2022. Vol. 5. P. 40.
4. Kozyrev N., Svetlichnyi A., Nepeivoda R., et al. Peeling away neutron skin in ultracentral collisions of relativistic nuclei // Eur. Phys. J. A. 2022. Vol. 58. P. 184.
5. Loizides C., Kamin J., d’Enterria D. Improved Monte Carlo Glauber predictions at present and future nuclear colliders // Phys. Rev. C. 2018. Vol. 97. P. 054910.
6. Allison J., Amako K., Apostolakis J., et al. Recent developments in Geant4 // Nucl. Instrum. Meth. A. 2016. Vol. 835. P. 186.
7. Kapishin M., et al. Studies of baryonic matter at the BM@N experiment (JINR) // Nucl. Phys. A. 2019. Vol. 982. P. 967.
8. Volkov V., Golubeva M., Guber F., et al. Performance of the scintillation wall in the BM@N experiment // Nucl. Instrum. Meth. A. 2025. Vol. 1077. P. 170529.

The opportunity of study light exotic states containing ssbar and ccbar quarks in hadron and ion collisions with Nuclotron deamss with the energies up to 12 GeV is discussed. It represents a good testing tool for the theories of strong interactions, i.e. QCD in both the perturbative and non-perturbative regimes, LQCD, potential models and phenomenological models. The analysis of light exotics containing ssbar and ccbar pair is given. The recent experimental data on such states are analyzed. Special attention was given to the low lying XYZ-particles. The attempts of their possible interpretation are considered. The results on physics simulations are obtained. Some of these states can be interpreted as tetraquarks with a hidden charm or strangeness. But much more data on different decay modes are needed before firmer conclusions can be made. These data can be derived from the experiments using the proton, deutron and ion beams with √S up to 4 GeV planned at Nuclotron facility of the NICA complex.

The Taishan Antineutrino Observatory (TAO), a satellite experiment of the JUNO project, is located at a short baseline from one of the reactor cores of the Taishan Nuclear Power Plant. Its primary objective is to achieve a high-statistics and high-energy resolution measurement of the reactor antineutrino energy spectrum. The detector contains a ton-scale liquid scintillator doped with gadolinium and operated at approximately −50 °C. Silicon photomultipliers provide a high-coverage light collection, enabling an energy resolution of about 2.8 % at 1 MeV. Data from the initial physics runs are analysed using a dedicated calibration programme and event reconstruction techniques, which allow precise characterisation of the detector’s energy response. Inverse beta decay candidates are identified via the prompt–delayed coincidence signature, while residual backgrounds are constrained using reactor-off data. A statistically significant reactor-correlated antineutrino signal is observed, and the measured prompt energy spectrum is consistent with the reference prediction within the current uncertainties. These results confirm the excellent performance of the TAO detector and provide a reference spectrum for the JUNO experiment, facilitate studies of fine spectral structures, and enable searches for light sterile neutrinos.

The DANSS reactor antineutrino spectrometer is located in close proximity to the power reactor of the Kalininskaya NPP (Russia). A lifting platform allows the detector position to be changed in the range of 11–13 m from the reactor core. More than 10 M neutrino events and the long-term experiment operation, covering 5 complete fuel campaigns, provide DANSS with rich experimental data, which is used for both fundamental and applied studies. Our results include:
the most stringent limit for sterile neutrinos at $\Delta m^2$∼1 eV$^2$,
new limits for Large Extra Dimensions,
a precise measurement of the 235U to 239Pu neutrino yield ratio,
the first precise monitoring of an industrial reactor’s power and fission fractions.

The DANSS detector recorded more than 10 million antineutrino events from a nuclear reactor in almost 10 years of continuous running. The data taking has stopped in February 2026 in order to perform a significant upgrade. The obtained data sample exceeds that of any other neutrino experiment in the world and features remarkably low contribution from the cosmic background below 2%. At the same time only moderate energy resolution limits the sensitivity of the experiment to the New Physics searches. The upgrade is aimed at the significant, more than 2 times, improvement of the energy resolution, along with the 70% increase of the sensitive volume. The talk will cover the details of the production and testing of the new scintillation counters for the sensitive volume, the anticipated changes in the DAQ system, the projected energy and coordinate resolution from the MC simulation, as well as the status and the schedule of the upgrade works.

We present measurements of the integral and spectral characteristics of the reactor electron antineutrino ($\bar{\nu}_e$) flux obtained with the iDREAM detector at Unit 3 of the Kalinin Nuclear Power Plant, which operates a VVER-1000 reactor. The measured positron spectrum from $\bar{\nu}_e$ interactions with protons in the iDREAM liquid scintillator is compared with a prediction based on the isotope-dependent $\bar{\nu}_e$ spectra of the KI model, a spatial model of the VVER-1000 reactor core, and a Monte Carlo simulation of the detector response. In the energy range of approximately $4$--$6~\mathrm{MeV}$, a local excess of the measured spectrum over the prediction is observed, confirming the presence of the reactor $\bar{\nu}_e$ spectral anomaly. The iDREAM data also confirm a decrease in the inverse beta-decay interaction rate normalized to the reactor thermal power as $^{235}\mathrm{U}$ is depleted and $^{239}\mathrm{Pu}$ accumulates in the reactor core during fuel burnup. Using the measured $\bar{\nu}_e$ interaction rate, the evolution of the $^{235}\mathrm{U}$ and $^{239}\mathrm{Pu}$ fission fractions is reconstructed while the contributions from $^{238}\mathrm{U}$ and $^{241}\mathrm{Pu}$ are kept fixed. These results are further used to obtain a model-dependent estimate of the relative change in the $^{239}\mathrm{Pu}$ mass in the reactor core over the course of the fuel cycle.

Most accurate antineutrino spectra from fission fragments of nuclear fuel fissile isotopes 235U,238U,239Pu,241Pu were obtained. These spectra were calculated when fitting experimental antineutrino spectrum by the calculated ones. As a result, high statistics experimental spectrum was described with the calculated one. New antineutrino spectra can predict inverse beta-decay cross section in reactor antineutrino flux with an accuracy of about 1%.

For the first time, the electron-antineutrino flux and energy spectrum of the BN-800 fast reactor are studied during fuel burnup for different core loading configurations. Three core configurations containing 16%, 50%, and 100% mixed-oxide (MOX) fuel are considered.The study of antineutrino emission from fast reactors with different fuel compositions is of interest both for understanding the formation of the reactor antineutrino signal and for developing non-invasive monitoring methods. An approximately 198-effective-day fuel cycle at a nominal thermal power of 2100 MW is simulated using the KIR-C software package. The calculated fission and neutron-capture reaction rates are used to study changes in the isotopic composition of the antineutrino signal, the integral flux, and the energy spectrum during fuel burnup. Increasing the MOX fuel fraction leads to a substantial redistribution of the fission contributions of uranium and plutonium isotopes; for the full-MOX core, approximately 82% of all fissions occur in 239Pu. The antineutrino flux and the shape of the energy spectrum depend on the core composition, while the differences relative to the VVER-1000 increase with increasing MOX fuel fraction. At the same time, the time evolution of the BN-800 antineutrino spectrum remains weak for all three configurations: changes in the spectral characteristics over the considered fuel cycle do not exceed a few percent.

The nature of isotopic anomalies in charge radii and atomic isomer shifts
at N=126 region.

I.N. Borzov, 1, 2, S.S. Pankratov, 1,3
1) National Research Centre”Kurchatov Institute”, Moscow, Russia
2) Bogolubov Laboratory of Theoretical Physics, JINR, Dubna, Russia
3) Moscow Institute of Physics and Technology, Dolgoprydny, Russia

The nuclear charge ms-radii and atomic isomer shift for the 211-219Bi isotopes are calculated within the self-consistent finite Fermi systems theory using the Fayans functional FaNDF0. A special attention is paid to the anomalous part of the functional. In contrast to our previous calculations [1], the full Hartree-Fock-Bogolubov (HFB) formalism is employed with the non-diagonal pairing.
The main impact on the kink in the isotopic dependence of radii at N=126, as well as on the isomer shifts comes from the occupancy factors of the neutron discrete and continuum quasiparticle states with principal quantum number n = 1, as well as the neutron pairing contribution to the proton central mean field potential. In contrast, in the RMF framework [2] the kink is determined exclusively by the contribution of the ν1i11/2 orbital assuming it is inverted with respect to the ν2g9/2 orbital which is not supported by the experiment. Importantly, our calculations successfully describe the unexpected negative isomer shift in 215Bi observed recently at ISOLDE (CERN) [3].

1. I.N. Borzov, S.V. Tolokonnikov, Physics of Atomic Nuclei 87, 423 (2024).
2. U. C. Perera , A. V. Afanasjev, and P. Ring. Phys.Rev. C 104, 064313 (2021).
3. M.D. Seliverstov, A. Barzakh, D. Fedorov, P. Molkanov, and V. Panteleev,
   Proceedings of the XXIV International Conference “Nucleus -2024”, 1–5 July (Dubna, 2024).

Inelastic nuclear collisions accompanied by gamma emission from excited nuclei serve as a valuable source of information regarding nuclear reaction mechanisms and the characteristics (energy, spin, parity) of nuclear levels. Notably, however, gamma radiation resulting from such collisions - occurring not only on the Sun but also on other stars - can be detected on Earth (see, e.g., [1]). The intensity of this radiation allows for an assessment of the concentration and energy of the colliding particles within stellar atmospheres. In principle, further information regarding the fluxes of colliding particles can be obtained, as the energy (frequency) of gamma quanta emitted in a specific direction depends on the trajectories of the colliding and outgoing particles. As a step toward acquiring such data, the characteristics of gamma radiation emitted at various angles relative to the reaction axis in the inelastic scattering of protons (with energies ranging from 5.44 to 25 MeV) by the ¹²C nucleus was calculated in [2] (the 2⁺ state 4.439 MeV was excited). The calculated gamma-line shapes (intensity versus energy) showed good agreement with the results of earlier measurements.

Evident expression for the differential cross section of the analogous 12C(n,n’γ) reaction—involving excitation of the same 4.439 MeV state—is presented in a recent study [3], alongside the results of measurements of this cross section. Using a more general approach to describing angular correlations—based on functions of three vectors that are independent of the choice of coordinate axes, as first described in [4]—we derived the double-differential cross sections for both the 12C(n,n’γ) reaction and the analogous 12C(p,p’γ). In our view, differential cross sections expressed in terms of such vector functions are better suited for calculating gamma-line shapes. This approach to describing triple angular correlations can be extended to other similar reactions, including those of astrophysical significance.

References
1. D.J. Forrest, R.J. Murphy. Solar Physics, 1988, v. 118, iss. 1, p. 123-135.
2. J. Kiener. Phys. Rev. C, 2019, v. 99, iss. 1, 014605.
3. P. Filonchik et al. Int. J. Mod. Phys. E, 2024, v. 33, iss. 12, 2441020.
4. L.C. Biedenharn. Pure and Applied Physics, v. 9 (Nuclear Spectroscopy, Edited by F.Ajzenberg-Selove), part B, 1960, section V, subsection C, p. 732 (Academic Press, New York and London).

Creation of transuranic nuclides in experimental pulsed neutron fluxes of high intensity (up to 10E+30 – 10E+31 n/cm2) is investigated in the kinetic model of the astrophysical r-process. The dynamics of the rapid nucleosynthesis (in the interval ~10E-6 s) is introduced when the process temperature decreases and is taken into account by correction of the cross sections at radiation capture of neutrons. In spite of the more lower fluxes and temperature compare to possible cosmological sites of superheavy isotope production (up tp 10E+40 n/cm2 and ~10E+9 K in case of binary star mergers, stripping matter in massive binary systems) an application of heavy (actinides) targets allows to ensure production of identifiable quantities of transuraniums up to 257Fm by multiple neutron capture (up to 19 neutrons for 238U targets). Subsequent correction of transuranium outputs after pulse termination is taken into account in beta-decays of neutron-excess nuclei.

The produced analytical analysis strongly indicated on the roughly linear dependence of the relation of isotope yields on the pulse neutron fluence. Agreement of calculated isotope relations with experiments is a criterion of possible fluence. Evaluation of the realized neutron fluence is the inverse problem. The task of yields modeling of neutron-rich isotopes (and inverse problem of the achieved fluence) during multiple neutron captures is solved in the developed ABM model, which takes into account the drop of the temperature during the expansion of matter with a linear velocity ~190 km/s. The model allowed to obtain good or satisfactory agreement with published US-experiment for pulse production of transuranic elements. In the simulation it was applied the 238U, 238Pa and 243Am targets according to declared results of the tests. It was proposed an algorithm for calculating dependence of isotope relations on fluence for complex targets. It was evaluated achieved fluences and obtained good agreement in isotope relation of seven large scale experiments.

[1] G. I. Bell. Phys. Rev. 139, B1207 (1965)..

[2] J. S. Ingley, Nucl. Phys. A 124, (1969) 130 (1969).

[3] V. I. Zagrebaev, A. V. Karpov, I. N. Mishustin, and W. Greiner, Phys. Rev. C 84, (2011) 044617.

[4] Yu. S. Lutostansky, and V. I. Lyashuk. Phys. At. Nucl. 88, 16 (2025)..

[5] V. I. Lyashuk, Results in Physics. Volume 56, (2024) 107234.

[6] V. I. Lyashuk, Physics of Particles and Nuclei Letters, 2025, Vol. 22, No. 2, (2025) 324.

Considered are different one-dimensional three-body systems in the universal
low-energy limit of zero-range two-body interactions.
Included are the two-component system with usual contact interactions and
three-component system with impenetrable particles.
Main attention is paid to the possibility to find analytical results and main
patterns of the dependencies of bound-state energies and scattering
characteristics on the parameters of systems (interaction strengths, masses
of particles, parity).

For a system with usual zero-range interaction, there are few known analytical results,
for example, for systems with infinite or zero strength of interaction
between identical particles and with equal mass particles or for one heavy
and two light particles [1].
In contrast, for a system with impenetrable particles due to correspondence
to the symmetrical case of usual zero-range model, it was possible to find
the bound-state solution in the diffraction-free (Bethe ansatz) form [2].
Moreover, this model for impenetrable particles is mathematically
identical to the problem of reflection and diffraction of the plane or
surface waves by an impedance wedge described in [3].
One more interesting problem to discuss is the scattering of dimer on a hard
wall [4] that corresponds to the three-body system in which
one particle has infinite mass.

[1] O.I. Kartavtsev, A.V.Malykh, S.A. Sofianos, ZhETF {\bf 135}, 419 (2009).

[2] O.I. Kartavtsev, A.V.Malykh, to be published.

[3] G. D. Maluzhinetz, Dokl. Akad. Nauk SSSR {\bf 121}, 436--439 (1958).

[4] X. Zhang, Sh. Tan, Phys. Rev. A {\bf 113}, 043312 (2026).

The angular momenta acquired by fission fragments are formed already at the stage of the compact dinuclear system. One of the sources of their excitation is collective rotational degrees of freedom associated with deviations of the fragments from the coaxial configuration. However, the transition from the collective motion of the system to the individual angular momenta of the fragments is not unambiguous: the result depends on the choice of coordinates used to describe the rotational motion and on which quantities are assumed to be conserved during such motion.
This issue is of particular importance for transverse oscillations, which are commonly identified with the bending degree of freedom. Geometrically, the corresponding motion can be represented as a change in the mutual orientation of the fragments with respect to the fission axis. However, such a description alone does not determine the distribution of angular momentum between the intrinsic rotation of the fragments and the rotation of the dinuclear system as a whole. This ambiguity leads to different effective moments of inertia used in fission models [1–4].
If the transverse motion is treated as an independent relative degree of freedom, conservation of the total angular momentum implies opposite directions of rotation of the fragments. The energy of such motion is characterized by the reduced moment of inertia constructed from the moments of inertia of the fragments themselves [1,2]. In this case, no additional orbital rotation of the dinuclear system is introduced, and the bending excitation is directly associated with oppositely directed angular momenta of the fragments.
An alternative approach to constructing the rotational degree of freedom arises when oscillations about the equilibrium rotational state of the dinuclear system are considered [3,4]. In this case, a change in the orientation of one of the fragments is accompanied by a rearrangement of the motion of the entire system. Consequently, part of the angular momentum associated with the excitation of the transverse motion is orbital. Depending on the scheme adopted, the rotation of either the light or the heavy fragment may be considered, compensated by a rotation of the remaining system.
From a physical point of view, this means that the same term, bending mode, may be used for motions having different angular-momentum structures. In the first case, the motion corresponds to pure relative rotation of the fragments, whereas in the second case, the excited degree of freedom contains an additional collective component. Therefore, a direct comparison of the results of different models based solely on the magnitude of the effective moment of inertia may be inappropriate. For the schemes considered in [3,4], it appears appropriate to use the term pseudo-bending motion, since the corresponding description includes a change in the orbital angular momentum.
This distinction manifests itself directly in the transition from collective dynamics to the observable spins of the fission fragments. In the statistical description of rotational degrees of freedom, the mean-square angular momentum is determined by the effective moment of inertia and the excitation temperature. Consequently, a change in the mechanical model of the bending motion, while keeping the other parameters of the system unchanged, leads to a change in the predicted fragment spins. At temperatures of the order of 1–2 MeV, the contribution of the considered degree of freedom may reach several units of ℏ, making it comparable with characteristic fragment-spin values.
In the present work, a systematic comparison of the effects of different descriptions of the rotational dynamics on the angular characteristics of fission products is performed. Within the framework of the cold-fission model, the reactions 238U(n,f) and 232Th(n,f), as well as the spontaneous fission of 252Cf, are considered. Different prescriptions for the moments of inertia of the fragments, corresponding to the hydrodynamic and superfluid limits, are employed. For each case, the quantities determining the formation of fragment spins and orbital angular momenta, as well as their correlations, are calculated.
The obtained results are compared with the calculations and experimental data presented in [5]. The analysis makes it possible to assess the extent to which the predictions of spin characteristics are determined by the properties of the fragments themselves and the extent to which they depend on the adopted description of the collective rotational degree of freedom. It is shown that the choice of the effective moment of inertia of the bending motion is not merely a formal element of the model and can lead to significant changes in the quantitative characteristics of the angular momenta of the fission fragments.
References
J. Randrup, R. Vogt, Phys. Rev. C 89, 044601 (2014).
J. R. Nix, W. J. Swiatecki, Nucl. Phys. 71, 1 (1965).
J. Randrup, T. Døssing, R. Vogt, Phys. Rev. C 106, 014609 (2022).
T. M. Shneidman et al., Phys. Rev. C 65, 064302 (2002).
J. N. Wilson et al., Nature 590, 566 (2021).

There exist a number of models for nuclear structures allowing for descriptions of various nuclear properties [1]. One of such models is based on the idea of nucleons inside a given nucleus lying in the folded Yukawa potential, accounting for the spin-orbit and the Coulomb interactions [2, 3]. The model can be adapted for different nuclei properties calculations [4].

The work presents calculated single particle nucleon energies of selected nuclei based on spherically symmetrical shape approximation for modified folded Yukawa potential. The proposed modification provides for a way of taking possible metastable single particle levels into account. Obtained energy levels are suitable to be used in combinatorial approaches of calculating level density of excited states of a nucleus in the frozen core approximation.

1. Ring P., Schuck P. The Nuclear Many-Body Problem. — New York : Springer, 1980. — (Texts and Monographs in Physics).
2. Bolsterli M., Fiset E. O., Nix J. R., Norton J. L. New Calculation of Fission Barriers for Heavy and Superheavy Nuclei // Physical Review C. — 1972. — v. 5, iss. 3. — p. 1050–1077.
3. Nix J. R. Calculation of Fission Barriers for Heavy and Superheavy Nuclei // Annual Review of Nuclear Science. — 1972. — v. 22, iss. 1. — p. 65–120.
4. Uhrenholt H., Åberg S., Dobrowolski A., Døssing T., Ichikawa T., Möller P. Combinatorial nuclear level-density model // Nuclear Physics A. — 2013. — v. 913. — p. 127–156.

Accurate knowledge of the magnetic field distribution is essential for precise momentum reconstruction of charged particles in the SPD experiment at NICA. Traditional interpolation of pre-computed field maps becomes computationally expensive for high-resolution grids and may be inaccurate in regions with sparse measurements.
A systematic comparative study of machine learning methods for approximating the three-dimensional magnetic field of the SPD detector is presented. The study covers a broad range of approaches, including neural networks and other algorithms. The magnetic field in this work was constructed using Monte Carlo simulation.
The results are presented and discussed, with recommendations for choosing a field approximation method depending on the available data and required precision.

The CEPC working point at the center of mass energy around 240 GeV corresponds to the largest cross section of the higgsstrahlung process and allows effective usage of the recoil mass technique for measurements of Higgs boson parameters. The interesting task is the search for invisible decays of the Higgs boson: H->ZZ*->4nu. The dijet final states of the process e+e-->ZH, where Z boson decays to quarks, have large branching fractions but quite large background contributions. In this work, a two-stage machine learning algorithm for separation of the invisible Higgs decay signal in dijet final states is presented. At the first stage, separate binary classifiers are trained on signal-background pairs for several dominating background channels. At the second stage, a combined classifier is trained using the outputs of the first-stage models as inputs. The study was done with full simulation and reconstruction of the signal and background processes by the CEPC software. The performance of the two-stage approach is compared with conventional kinematic selections, and its effect is discussed on the upper limit on the branching fraction of the Higgs boson invisible decay.

The Joint Institute for Nuclear Research (JINR) is approaching the commissioning and operational readiness of the NICA (Nuclotron-based Ion Collider fAcility) mega-science accelerator complex. One of its future detectors is the SPD (Spin Physics Detector), designed to study the spin structure of nucleons. The Range System (muon system) is an integral part of the detector, used for muon identification and coarse hadron calorimetry. This report is devoted to the simulation and reconstruction of events in the SPD Range System using the SpdRoot software framework. In particular, it provides an overview of machine learning algorithms, such as DBSCAN, BDT, and CNN, applied to clustering and particle classification tasks. These results provide the foundation for critical measurements, such as charmonium probing in the SPD experiment.

Fast calorimeter simulation requires accurate generative models and meaningful
measures of physical fidelity. We integrate physics-supervised distributional evaluation and residual regularization into our conditional diffusion pipeline for the first time. Shower generation is conditioned on particle entry coordinates and momentum, allowing the model to represent variations in detector response across incident-particle configurations.

The evaluation uses a Frechet Physics Distance - FPD - computed in a representation learned by a network trained to predict particle kinematics and shower-shape observables. Comparing the means and covariance matrices of reference and generated embeddings connects mathematical distributional assessment with physically relevant features, complementing PRD-based scores and KL-divergence diagnostics. Physics supervision guides feature learning towards quantities relevant to shower characterization, while the covariance comparison incorporates correlations between learned features. The diffusion model predicts clean shower maps in a logarithmic energy representation, with a timestep-weighted penalty on negative predictions added to its reconstruction objective. This introduces a soft nonnegativity constraint during training while retaining DDIM sampling without a physics solver.

On the validation sample, the revised pipeline achieves an FPD of $0.058$ after
clipping negative deposits, compared with $0.889$ under the same evaluation
protocol. Both Energy and Physical PRD AUC scores exceed $0.999$, with the latter
evaluated on events with finite shower-shape features. PRD is computed on raw outputs, preserving a separate assessment before clipping. Explicit audits additionally examine negative deposits, sparsity, and total deposited energy, identifying discrepancies not fully reflected in aggregate
scores. These checks help distinguish agreement in the selected feature spaces from physical admissibility of individual generated showers. The resulting framework supports systematic model comparison and targeted improvements to calorimeter simulation, with controlled ablations needed to isolate the contribution of residual regularization.

A Graph Attention Neural Network (GANN) for particle track clustering by events in time slices obtained at the Spin Physics Detector (SPD) of the Nuclotron-based Ion Collider fAcility (NICA) is presented. A novel approach is applied to time slice processing at high particle multiplicity and pile-up. The model is trained using a hierarchical approach and evaluated on time slices generated by the Monte Carlo technique according to the SPD experiment configuration as close as possible at the moment. The model architecture includes a graph encoder and an edge classifier, both of which use the message-passing principle and iteratively structured approach. The GANN exhibits high performance in track clustering by events for the SPD simulation, achieving 90% accuracy and 90% precision and recall.

Holographic QCD models describe strongly interacting matter through a five-dimensional gravitational background. In Einstein–Maxwell–Dilaton models, the warp factor A(z) deforms the AdS metric and affects QCD thermodynamics, the phase structure, and heavy-meson spectra. Such models are commonly calibrated using lattice-QCD data [1, 2] in contrast with employment on the experimental data.

In this work, we develop a differentiable-programming framework for the inverse reconstruction of the warp factor in AdS/QCD using PyTorch [3]. We consider parameterized families of phenomenological ansatz, in particular combinations of logarithms of polynomials. Their parameters are optimized with gradient-based methods, in particular Adam [4] and L-BFGS-B [5], while automatic differentiation provides gradients through the numerical pipeline without finite-difference approximations.

For each parameter set, we construct the holographic background and calculate the phase-transition curve in the temperature–baryon-chemical-potential coordinates. Its deviation from the chemical freeze-out line defines the thermodynamic loss; the method is tested using both an analytic freeze-out parameterization and experimental data from the relativistic nucleus-nucleus collisions [6]. Heavy-meson masses are calculated following [7] using the aforementioned ansatz'. The constraints on the meson masses are included through gaussian process emulator differentiable surrogate [8] that approximate the dependence of meson masses on the background parameters. The total loss combines information on the thermodynamics and meson spectroscopy along with regularization on the critical endpoint (CEP) position to achieve smooth and physically admissible warp factors. The procedure reconstructs families of warp factors compatible with chemical-freeze-out and spectroscopic constraints, allowing us to assess the stability and non-uniqueness of the inverse problem.

References

[1] X. Chen and M. Huang, “Flavor dependent critical endpoint from holographic QCD through machine learning,” arXiv:2405.06179 [hep-ph] (2024).

[2] M. T. Arun and R. Pal, “Learning holographic QCD with unflavored meson spectra,” J. High Energy Phys. 06 (2026) 226

[3] A. Paszke et al., “Automatic differentiation in PyTorch,” J. Mach. Learn. Res. 18 (2018) 1, arXiv:1701.06757 [cs.LG].

[4] D. P. Kingma and J. Ba, “Adam: A Method for Stochastic Optimization,” in 3rd International Conference on Learning Representations (ICLR 2015), San Diego, CA, USA, May 7-9, 2015, Conference Track Proceedings, 2015.

[5] D. C. Liu and J. Nocedal, “On the Limited Memory BFGS Method for Large Scale Optimization,” in Mathematical Programming, vol. 45, pp. 503–528, 1989.

[6] X. Luo and N. Xu, “Search for the QCD critical point with fluctuations of conserved quantities in relativistic heavy-ion collisions at RHIC: An overview,” Nucl. Sci. Tech. 28 (2017) 112

[7] B. Toniato, D. Dudal, S. Mahapatra, R. da Rocha, and S. S. Jena, “Holographic QCD model for heavy and exotic mesons at finite density: A self-consistent dynamical approach,” Phys. Rev. D 111, 126021 (2025)

[8] M. C. Kennedy and A. O'Hagan, “Bayesian calibration of computer models,” J. R. Stat. Soc. Ser. B Stat. Methodol. 63 (2001), no. 3, 425–464.

Focusing aerogel ring-imaging Cherenkov (FARICH) detectors require the reconstruction of sparse photon patterns in the presence of background caused by a photosensor dark count rate. We present the Track-Conditioned Ring Assignment Transformer (TCRAT), an attention-based model that simultaneously assigns photon hits, reconstructs the particle velocity, and performs particle identification in a FARICH detector.

Each event is represented as an unordered set of pixelized hits. A track-conditioned query identifies hits compatible with the charged-particle trajectory, while a separate background query models unassigned hits. The method does not impose a circular or elliptical ring shape on the photodetector plane, allowing it to account for angle-dependent distortions caused by refraction at the aerogel-air boundary.

The method was evaluated using simulated single-particle events in the FARICH detector concept for the future Super Charm-Tau Factory, including track and momentum measurement uncertainties and dark-count rates ranging from zero to 1 MHz/mm². When trained across the full background range without an explicit dark-count-rate input, TCRAT maintained an RMS90 β resolution of about $(4.6\times10^{-4})$ and a balanced particle-identification accuracy of about 94% across the studied noise conditions. Providing the dark-count rate explicitly did not improve the reconstruction quality, indicating that the model can infer the relevant background conditions directly from the event hit pattern.

The talk presents the first experience of applying deep neural networks to simulate the responses of microstrip GEM detectors used in the BM@N experiment at the NICA accelerator complex (JINR). The preparation of the training dataset based on data obtained using classical Monte-Carlo simulation methods implemented in the BMNROOT software is discussed. The advantages of the neural network approach are considered, particularly the reduction in detector response generation time compared to traditional methods. The quality of the generated responses is also compared with reference simulations.

GRB 221009A was a remarkable gamma-ray burst; it is sometimes referred to as “the brightest of all time” (BOAT). In this talk we consider two peculiar components of observable gamma-rays from GRB 221009A: 1) a high energy “echo” of the GRB
prompt emission phase produced by neutrons from photohadronic interactions inside the fireball with subsequent interaction of these neutrons with the material of the star forming region (SFR) and 2) external Compton (EC) radiation due to the scattering of the accelerated electrons on the radiation reflected from the SFR material. We show that both components are potentially observable. In addition, we discuss the shape of the primary (intrinsic) gamma-ray spectrum of GRB 221009A and the nature of the 300 TeV gamma-ray-like event detected by the Carpet-3 array in temporal and angular coincidence with GRB 221009A. Some details are available in astro-ph/2604.10378.

Some neutron stars are located in low-mass X-ray binaries (LMXBs), i.e. have low-mass companions. In these systems, matter from the companion is transferred via Roche-lobe overflow and accretes onto the neutron star. The accretion process can be either transient or persistent. During accretion, the previously accreted material is compressed under the weight of newly accreted matter. In the outer crust, the pressure is primarily determined by degenerate electrons; consequently, this compression leads to an increase in the electron chemical potential. Such an increase can drive electron capture reactions out of equilibrium. Previous studies investigating the nuclear evolution of accreted matter in the neutron star crust can be divided into two groups: (1) those that consider variable accretion rates but assume electron capture reactions occur instantaneously; and (2) those that account for finite reaction rates but assume a steady (stationary) accretion rate.

A recent study [1] examined non‑stationary accretion while accounting for finite electron capture rates. However, the capture rate was computed using the zero‑temperature approximation. Under this approximation, the reaction rate is exactly zero below the threshold density and increases sharply above it. Using this approach, the authors of [1] demonstrated that the crust structure is non‑stationary. During an accretion episode, the composition of the outer crust evolves away from beta equilibrium due to the accumulation of nuclei above the threshold. During a quiescent state, these accumulated nuclei are burnt out, which results in a nearly beta‑equilibrium composition restored before the next accretion episode begins. This leads to a cyclical pattern in the crust’s composition.

In this work, we investigate the dynamics of nuclear reactions under conditions of non‑stationary accretion, incorporating finite‑temperature reaction rates. We show that this approach substantially alters the physical picture. Due to thermal excitations, electron capture reactions become effective even below the nominal threshold density. At the same time, the reverse reaction is suppressed: it is inhibited by a subsequent electron capture on the daughter nuclei. This second capture is superthreshold because of nuclear pairing effects – the daughter nucleus is odd‑odd, so the threshold density is low. Furthermore, the dependence of the reaction rates on density becomes less pronounced. Consequently, the composition of the outer crust evolves more slowly compared to the model presented in [1]. As a result, the composition at the onset of an accretion episode depends on the long‑term accretion history of the system. In particular, this effect can lead to a substantial release of energy during a strong accretion episode as a result of burning of nuclei that accumulated in the crust during earlier accretion.

The work is supported by Russian Science Foundation (grant No. 22-12-00048-P).

[1] Suleiman, L., Zdunik, J. L., & Haensel, P. (2024). Layers of electron captures in the crust of accreting neutron stars. A&A, 690, A301.

Among the scenarios for the evolution of various astrophysical objects in which the conditions necessary for the r‑process to occur can be realized, the process of neutron star mergers in a close binary system is currently considered the main one [1]. This scenario largely depends on the masses of the objects included in the system and can develop in different ways: 1) If neutron stars have approximately the same mass, a merger occurs, accompanied by the ejection of neutron‑rich matter in the equatorial plane and in the wind from the hot, massive neutron star [2]; 2) If the masses of the neutron stars differ significantly, the evolution of the neutron star system follows a stripping scenario [3], in which, in particular, the nucleosynthesis of heavy elements proceeds differently [4,5].
The first ideas about the merger of a neutron star (NS) and a black hole associated with short gamma-ray bursts (GRB) were put forward by Lattimer and Schramm [6]. The scenario of the merger of two neutron stars was developed by Clark and Eardley [3]. In the last paper not only the merging of two neutron stars was discussed, but also proposed a stripping scenario involving the loss of mass by a minimum mass star.
In both scenarios, two neutron stars orbiting each other must come closer due to the loss of angular momentum caused by the emission of gravitational waves. What is the difference between the merger and tidal disruption mechanisms? The merger mechanism is as follows: having approached each other to a sufficient distance, the neutron stars merge into a single object — a black hole or a rapidly rotating neutron star — over several orbits. At the same time, part of the matter may be ejected from the system due to tidal interaction. Furthermore, due to the extreme acceleration of the rotation of the matter and its heating, a highly collimated ejection of matter can form — a jet — and part of the matter of the merged neutron star can evaporate in the form of a wind. This picture of neutron star mergers is currently generally accepted, although many of its details remain unclear.
The fundamental difference between the stripping mechanism and a rapid merger lies in the prolonged (many orbits of the binary system) transfer of matter from one star to the other. Note that for this scenario to be realized, a sufficient asymmetry in the masses of the components of the binary system is required. As the neutron stars approaches, the component with the smaller mass first fills its Roche lobe, since it has a larger radius, and begins to transfer mass to the more massive companion through the inner Lagrange point. The asymmetry of the system increases, and the distance between the stars increases due to the approximate conservation of the system’s angular momentum. However, the transfer does not stop (it is stable) due to the loss of angular momentum through the emission of gravitational waves and the increase in the radius of the NS with the smaller mass.
As a result of the exchange, the mass of the heavier star (M1) increases, while its radius remains approximately constant or decreases, and the mass of the lighter NS (M2) decreases while its radius increases. When M2 reaches the value corresponding to the minimum possible mass of the NS (about 0.1 solar masses), an explosion occurs, which leads to the destruction of the low‑mass NS.
This report examines the nucleosynthesis of heavy nuclei under the influence of neutrons (the r‑process) in the inner crust of a low‑mass neutron star (LMSN), which loses mass due to the transfer of matter onto a more massive companion neutron star (the stripping scenario) and explodes upon reaching a hydrodynamically unstable configuration [7].
It has been shown that the schock wave generated during the destruction of the MMNZ heats the outer shell of the inner core to high temperatures, and the r‑process transforms into explosive nucleosynthesis. Since the cross‑sections of induced fission increase by orders of magnitude when the temperature rises to values of T9>5, and given the persistently high neutron density, an instantaneous (t~3–5 ms) fission flash of the actinides formed in the r‑process occurs. The composition of the resulting fission product nuclei largely depends on the model of the mass distribution of fission products and represents a new initial composition for the r‑process, which resumes after further expansion of the matter and a drop in temperature.
The work was carried out as part of fulfilling the state assignment of the National Research Center “Kurchatov Institute”.
LITERATURE
1. J. J. Cowan, et al. // Rev. Mod. Phys. 2021. V. 93. id. 15002.
2. S. Rosswog, Philosophical Transactions of the Royal Society A. 2013, V. 371, № 1992, 20120272.
3. J. P. A. Clark and D. M. Eardley // Astrophys. J. 1977. V. 215. P. 311.
4. I.V. Panov, A.V. Yudin // Astronomy Letters. 2020. V. 46. P. 518.
5. A. Yudin, N. Kramarev, I. Panov, A. Ignatovskiy // Particles. 2023. V. 6. P. 784.
6. J.M. Lattimer, D.N. Schramm // Astrophys. Lett. 1974. V. 192. P. 145.
7. S. I. Blinnikov, D. K. Nadyozhin, N. I. Kramarev, A. V. Yudin // Astronomy Reports. 2021. V. 65. P. 385.

Axion-like particles (ALPs) are a class of hypothetical bosons beyond the standard model of particle physis, which are
very weakly-interacting and long- lived. Since many ALPs may be produced in hot plasma in supernovae (SNe), a nearby
SNe Ia can be used as a probe of ALPs. It is desirable to predict the ALP emission from SNe Ia to discuss a possible
constraint that can be obtained from the event. ALPs may convert into photons and back in the magnetic field in the
intergalactic space and galaxies. It is hence possible to constrain the ALP parameters by γ-ray observations of a nearby
astronomical object which emits a lot of ALPs. Here, we calculate the ALP emission from type Ia SNe and take into the
account the light range of ALPs mass. Using the SN Ia model, we consider the issue of detection a photon flash from
SNe Ia

Abstract: The paper theoretically investigates the equilibrium structure of neutron stars consisting of degenerate relativistic neutron gas, based on the equation of radial mass distribution. The thermodynamic properties of a relativistic Fermi gas are studied, and a relationship between the compressibility coefficient and the particle concentration is established without taking nuclear forces into account. The mass distribution equation is numerically solved for the pulsar PSR J0740+6620, and its radius, as well as the radial distributions of density, pressure, and Fermi energy, are determined. A comparison of relativistic and non‑relativistic models was carried out, showing that taking relativistic effects into account leads to a denser star with a smaller radius. Based on numerical calculations, the Oppenheimer–Volkoff limit was estimated.

Keywords: neutron star, degenerate relativistic neutron gas, radial distribution of the star’s mass.

Neutron stars are giant cores consisting of degenerate neutron gas, primarily bound by gravitational forces. The density distribution of stellar matter is examined using the example of the pulsar PSR J0740+6620, whose mass is (2.08  0.07) times the mass of the Sun [1].
The radial mass distribution function m(r) of an adiabatic star in the absence of rotation obeys the equation [2]:
m^{″}-\frac{2}{r}m^{\prime }+\frac{G}{4\pi }\kappa {\left(\frac{m^{\prime }}{r^{2}}\right)}^{2}m=0, (1)
where κ is the compressibility of the substance, G is the gravitational constant. It satisfies the boundary conditions: m(0)=0 and m(R)=M , where M is the mass of the star, and R is its radius. The compressibility of a degenerate relativistic neutron gas is expressed as [3]:
\kappa =\frac{9}{\pi }\cdot \frac{(ch)^{3}}{8E_{0}^{4}}\cdot \frac{(1+x^{2})^{1/2}}{x^{5}}, где x=\frac{hc}{2E_{0}}{\left(\frac{3n}{\pi }\right)}^{1/3}. (2)
Here, n is the particle concentration; E0 is the rest energy of the neutron; h is Planck’s constant; c is the speed of light. In the non‑relativistic approximation x<<1.
The numerical solution of equation (1), taking into account (2), under the given boundary conditions, allows one to calculate the density distribution
\rho (r)=\frac{m^{\prime }}{(4\pi r^{2})} and other parameters of the star. The figure 1 shows the density distribution curves for PSR J0740+6620 in the relativistic (red solid line) and non‑relativistic (blue dashed line) models.

Fig 1. The dependence of density (kg/m³) on the radial variable (km).

In the non‑relativistic model of PSR J0740+6620, the radius is 11.8 km, and in the relativistic model – 10.3 km, which is quite comparable to the gravitational radius of the star in \frac{2GM}{c^{2}}=6.14 km. This indicates that a star with a mass of 2.8 M☉ is quite close to gravitational collapse.

Literature

1. Fonseca, E.; Cromartie, H. T.; Pennucci, T. T.; Ray, P. S.; Kirichenko, A. Yu; Ransom, S. M.; Demorest, P. B.; Stairs, I. H.; Arzoumanian, Z.; Guillemot, L.; Parthasarathy, A. (1 July 2021). Refined Mass and Geometric Measurements of the High-mass PSR J0740+6620. The Astrophysical Journal Letters. 915 (1): L12. arXiv: 2104.00880. doi:10.3847/2041-8213/ac03b8.
2. Джалмухамбетов А.У. Уравнение радиального распределения вещества звезд и планет //Тез.докл. конф-ции «Геометрия. Управление. Экономика» (г.Астрахань, 15-26 августа 2011г.).– М.: ИПУ РАН, 2011.– С. 13.
3. Шмакова А.М., Джалмухамбетов А. У. Термодинамические свойства вырожденного релятивистского ферми-газа //сб.научн.статей «Перспектива».– Астрахань: Астраханский гос.ун-т», 2023.– С. 15 – 18.

While Standard Model extensions such as Supersymmetry have long provided promising candidates, the absence of supersymmetric particle signals at the LHC and contradictory results from direct detection experiments motivate exploration of alternative scenarios. The hypothesis of composite dark atoms — electrically neutral atom-like bound states formed by stable doubly negatively charged particles with primordial helium nuclei — offers a promising framework to address the challenges in direct dark matter detection. We present self-consistent quantum-mechanical numerical model for describing the three-body interaction between X-helium (XHe) dark atoms and nuclei of ordinary matter, bridging cosmoparticle physics, nuclear physics, and experimental dark matter searches. The methodology incorporates nuclear, Coulomb, centrifugal, and Stark interaction potentials, enabling precise reconstruction of the effective interaction potential for XHe with sodium and iodine nuclei. Our results reveal a crucial selectivity: while the effective potential for sodium supports the radiative capture of the sodium nucleus by the dark atom into a single low-energy bound state with binding energy in the 1–6 keV range, consistent with the DAMA/LIBRA annual modulation signal, the corresponding radiative capture rates for iodine are substantially suppressed. This selectivity of modulation signal generation in the detector depending on the target nucleus naturally explains the observed signal in NaI detectors and its absence in experiments using heavier target nuclei, while satisfying experimental constraints on high-energy gamma emission. The results obtained validate the dark atom hypothesis as a coherent resolution to long-standing puzzles in dark matter direct searches. The developed model establishes a framework for interpreting experimental results and for future investigations of composite dark matter candidates.

The process of double Compton scattering, $e \gamma \to e \gamma \gamma$, in the presence of a strongly magnetized, both charge-asymmetric and charge-symmetric electron plasma is considered. The amplitude of the process is written out and
the selection rules for photon polarizations are found.By solving the kinetic equation, an estimate of the efficiency of polarized photon production is obtained.

This paper discusses the historical evidence for the light jets from the central Super Massive Black Hole of Galaxy in the 4th and 14th centuries. We suggest that the apparitions of a "lightening cross" recorded in 312, 351, 1317 and 1377 years were caused by the line of two jets beamed back-to-back from the center of Milky Way (MW), which is crossing the visible projection of the Galaxy disk. All historical accounts give precise time and geographical locations, where from X-crosses was seen: in the vicinity of Rome, in Jerusalem, in Tver' (the vicinity of Moscow) and in night sky over Moscow, respectively). The positions of the Sun (or the Moon) were also mentioned in the Middle Age manuscripts. These positions coincide with the location of the MW center on the sky map in these specific places and dates, as it is shown with the help of Wolfram Astronomy visualization instruments.As it was recently found from media, another memorial for MW jet of 4th century might be geoglyph on the rocky cliff, which is situated in shores of Paracas Bay in Peru. We suggest that the gap between jet activity events is about thousand years. The X cross in the sky was mentioned by Plato in {\it Timaeus}, but he can not be eyewitness and could only take this from the narratives of older ancient sages. The X cross pictures are multiply stamped on Roman coins. The processes in Galaxy are often periodic because of multiple orbital movements, so we should consider the millennium periods in the climate changes as well. There are specific variations that are repeated every thousand years. Variations in temperatures that are described in this work can be explained with reactions of Sun on the waves of astropaticles from Galaxy center: HE protons, light mass particles, neutral Baryonium Dark Matter (BDM) or absence of any radiation.The most dangerous periods of BDM conglomerates arrivals, which suppressed the Sun activity, happened at approximately 6th and 16th centuries and were named Little Ice Ages. Now, due to our hypothesis, the Earth is living at the same hottest period as it were in the beginning of 1st or 11th centuries. But the continuation of periods should not be repeated precisely, because the QCD interactions are the subject of strong fluctuations.

The QCD analysis of the available data of KEDR, BESIII and CLEO Collaborations
for the e^+e^ to hadrons total cross-sections in different orders of perturbation theory is analysed. The existence of the tension between KEDR and BESIII data is emphasized with the preference to KEDR Collaboration data . The obtained values of QCD coupling constant are compared to other world average extractions . The
material is based in part on the results of the recent work A.~L.~Kataev and K.~Y.~Todyshev,``Perturbative QCD fitting of KEDR and BESIII $e^+e^-$ data for R(s) and $α_s$ determination,'' Natural Sci. Rev. \textbf{3} (2026), 100801
[arXiv:2603.29803 [hep-ph]].

Multiparticle production still attracts our attention. Simulation by using Monte Carlo event generators is performed before planning any experiment. But it often overestimates (or underestimates) experimental data.
Of all multiparticle processes, $e^+e^-$ annihilation is the theoretically cleanest, proceeding via an intermediate virtual photon or $Z^0$-boson followed by $q\bar q$ pair creation. QCD describes well the development of
$q\bar q$ cascade as marcovian branching process.
The transformation of quarks and gluons into observable hadrons occurs at hadronization, to which perturbation theory is no longer applicable. The choice of a scheme for it is based on experimental data. Convolution of cascade and hadronization allowed us to describe the multiplicity. This model is called the gluon dominance model.
Several decades have passed since a series of e+e− annihilation experiments were
carried out. The hadron and heavy ion research revealed many new results.
That is why it appeared necessary to analyze multiplicity n e+e−-annihilation again

We investigate a model with a gauge boson of the baryonic U(1)_B group.

Relevance: Problems of dark matter and baryon asymmetry of the Universe

Objectives:
-Construction of the Lagrangian for baryon‑photon interactions with hadrons at energy scales typical of current detectors.
-Calculation of the baryon‑photon production cross section in the main channels.
-Estimation of the parameters of visible decays.
-Estimation of the sensitivity of current detectors.

Methods:
-We derive the mixing form factors of the baryon‑photon with vector mesons from the chiral sigma model.
-Low‑energy theory (TiMoFey detector): within chiral theory, we take into account resonances that contribute at the characteristic energy scale. We calculate the baryon‑photon production cross section in the main channels (πN and NN collisions).
-High‑energy theory: to calculate the production cross section in pp collisions at a higher energy scale, we use the tensor pomeron exchange notation.

Results:
-We determine the sensitivity of the TiMoFey detector.
-Also we consider general vector and axial vector particle (coresponding to arbitrary U(1) group, but not only baryon). We obtained decay channels and nucleon vertexes for such models.

Plans:
-The sensitivity of high-energy detectors will be determined in the near future with the approach of the interference exchange.

In this talk an overview is presented of a method based on the use of exact axial anomaly relations for investigating transition form factors $\pi^0,\eta,\eta'\rightarrow\gamma\gamma^{(*)}$ in the both space- and time-like regions. This method allows to examine the nonperturbative gluon matrix element $\langle 0 |G\tilde{G}|\gamma\gamma^{(*)} \rangle$ and obtain and describe main features of this matrix element. This method can be applied to study another processes, like $\pi^{0},\eta\rightarrow \nu \bar{\nu} \gamma$ Dalitz decays.

A brief review of the z-scaling concept for the analysis of hadron production over a wide range of hadron and nuclear collision energies is given. The concept is based on the fundamental principles of self-similarity, locality, and the fractality of hadron interactions. The notion of the fractal dimension of hadrons and nuclei, which is an important ingredient of the z-scaling concept, is discussed in the context of searching for new physics at small scales. In the z-scaling approach, the hadron spectrum is described by the scaling function Ψ(z) as a function of the self-similarity variable z. This variable is expressed via the momentum fractions of colliding particles and scattered constituents fragmented to produce inclusive particles, the structural and fragmentation fractal dimensions, the multiplicity density of negative particles, and a model parameter interpreted as the specific heat of the produced medium. Properties of Ψ(z) including its energy, angular, multiplicity, and flavor independence, are discussed. The shape of the scaling function reveals a power law at low and high z. A microscopic scenario of hadron production in terms of fractalons was given. The z-scaling scheme is used to study the dependence of momentum fractions and recoil mass on the collision energy, transverse momentum, and mass of the produced inclusive particle.

A brief overview of QCD analytic coupling is presented, mainly
following the recent results. An application to the pion-photon
transition form factor is demonstrated.

We construct simple analytical solutions of RG equations for the running couplings $\alpha_s$ and $y_{top}$ in the asymptotic regime. These solutions have explicit form, contain only logarithms and no special functions and subsequently sum up the leading, subleading, etc logarithms in all orders of PT. While the effect of $y_{top}$ on the running of $\alpha_s$ happens to be negligible, the role of $\alpha_s$ on the running of $y_{top}$ is essential, the account of higher orders gives a noticeable contribution.

The formation of spectral-spatial distortions of cosmic microwave background radiation near primordial black holes at redshifts 100-1000 is considered. After hydrogen recombination, the radiation from these objects leads to the significant increase in the population of the hydrogen subordinate levels in their surrounding environment. Consequently, this allows for the observation of a Fraunhofer-like absorption spectrum in the cosmic microwave background. These subordinate hydrogen lines currently lie in the radio wavelength range. Оne should observe circular absorption or emission features around the objects with small angular sizes.

Primordial black hole (PBH) production is investigated in a chaotic inflation model with a massive inflaton whose potential $V_0 + m^2\varphi^2/2$ contains a localized bump. The presence of the bump temporarily slows down the inflaton motion and leads to high, narrow peaks in the density perturbation spectrum. The density perturbation spectrum and the resulting PBH mass function are calculated numerically, showing that the model can produce PBHs with characteristic masses around $10^{20}$ g.

Constraints on the PBH abundance arising from Hawking radiation and its heating of interstellar dust are further studied. The obtained PBH mass spectrum is approximated by a parabolic distribution, allowing the dependence of the constraints on the width of the mass function to be investigated. Both a homogeneous cosmological PBH distribution and a Navarro–Frenk–White Galactic halo distribution are considered. The resulting constraints are found to depend strongly on the width of the PBH mass function: broader mass functions are subject to substantially stronger constraints, while narrow mass functions around $10^{20}$ g can still allow a significant PBH contribution to dark matter.

Black holes formed in the early Universe (primordial black holes, PBHs) may simultaneously explain several astrophysical anomalies. These include, for example, the existence of supermassive black holes in the young Universe ($z>6$, Mazzucchelli C. et al., (2017, ApJ)) and black holes with masses of $\sim30 M_\odot$ detected by gravitational-wave observatories (LVK Scientific Collaboration et al. 2025) that fall into the “forbidden” mass gap for remnants of stellar collapse (Abbott R. et al. (2020b, Phys. Rev. Lett.)). PBHs may also contribute a fraction of the dark matter (DM), although for solar mass range it is already constrained by $\leq 10\%$ (P. Mroz et al. (2024, Nature)).

In the basic scenario, it is assumed that PBHs are spatially uncorrelated. However, if PBHs are derived from large non-Gaussian tails of density contrast, they can be spatially clustered at birth (Animali et al., (2024, JCAP)). There are other models that lead to clustering such as the modified Affleck-Dine mechanism (Kawasaki et al., (2021, JCAP)). The clustering of PBHs would change the merger history of PBHs, therefore it is important to study such systems.

We present a numerical study of dynamical evolution of isolated primordial black hole clusters. We use mass distribution of PBHs derived from LIGO-Virgo-Kagra data fit (Dolgov et al., (2020, JCAP); Andres-Carcasona et al. (2024, Phys. Rev. D.)). The evolution of clusters was computed using the direct N-body code $\textbf{NBODY6++GPU}$ and takes into account orbit-averaged gravitational wave emission. We explore how the parameters of such clusters affect the merger rate and masses of merging binaries.

This work examines the impact of primordial black hole clustering on the dynamics of their mergers. Gravitational perturbations from neighboring black holes within a cluster perturb the orbital parameters of binary systems, effectively excluding them from the population of merging binaries. This, in turn, characteristically alters the merger history compared to the non-clustered case, which manifests both in the redshift evolution of the merger rate and in the spectrum of the stochastic gravitational-wave background. We discuss how these effects can be tested by future gravitational-wave observations.

One possible mechanism for the formation of primordial black holes (PBHs)
is the collapse of domain walls. Previous theoretical models considered PBH
formation in the spherical approximation, whereas full field-theoretic
simulations of non-spherical domain walls clusters are too computationally
demanding to accumulate sufficient statistics.

In this work, we derive the equations of motion of a domain wall in the
thin-wall approximation and propose a numerical method for evolving the
wall surface using triangular mesh algorithms. For prescribed field configurations of a cluster, the method yields the differential mass spectrum of the resulting PBHs.

Based on a Monte Carlo ensemble, we obtain $dN/dM \propto M^{-\alpha}$
with $\alpha = 2.31^{+0.01}_{-0.02}$, significantly larger than the
theoretical value $\alpha \approx 1.75$ for spherical-wall collapse,
indicating a larger fraction of low-mass PBHs. This deviation is
presumably due to the fragmentation of walls with complex geometry, which is absent
in the spherical approximation.

The interaction of primordial plasma with a closed domain wall during the radiation-dominated stage of the Universe is considered. When the plasma temperature drops below a threshold value determined by the parameters of the wall potential, the wall becomes opaque to particles, and the plasma becomes locked inside. The subsequent evolution of the bubble is studied using relativistic hydrodynamical simulations of the enclosed plasma and its influence on the collapsing wall. The influence of the radiated energy on the BBN is estimated.

High-precision measurements of pulsar timing arrays (PTA) allow us to probe stochastic gravitational wave background (GWB), which is generated by various processes in the Universe. Domain walls (DWs) that emerged in the early Universe could be one of the hypothetical sources of such GWB. In this work, two different models of DWs are considered. Such objects produce GWB with a distinctive power spectrum. In this work we develop an algorithm to search for such signals in PTA datasets. The algorithm has been validated on a simulated pulsar timing data. We apply the analysis scheme on the latest data release of the European Pulsar Timing Array collaboration (EPTA). We present obtained estimates and constraints on physical parameters, which describe the evolution of melting DWs and biased DWs.

TBA

TBA

Spontaneous breaking of charge symmetry in elementary particle interactions, which could lead to the
universe equally populated by matter and antimatter, is critically discussed. It is argued that our model
of PBH formation of 1993, predicts noticeable population of galaxies with antimatter. Observational data
supporting this prediction are presented. Some new effects induced by antimatter presence in the Milky
Way are considered.

In this work, we investigate the cosmic expansion history and address the Hubble tension within a bulk-viscous cosmological model in 𝑓(𝑅,𝐿𝑚) modified gravity. Considering the specific functional form 𝑓(𝑅,𝐿𝑚) = αR + β𝐿𝑚, we derive the modified field equations using a flat Friedmann-Lemaitre-Robertson-Walker (FLRW) metric in a matter-dominated era with bulk viscosity 𝛱 = −3 𝜁 𝐻. We utilize recent independent observational datasets, including Cosmic Chronometers (CC), Pantheon+SH0ES Type Ia Supernovae, and DESI Baryon Acoustic Oscillations (BAO), to perform a robust Bayesian learning analysis via the PyMC3 library. The dynamical features of the model—including the effective energy density, cosmic pressure, effective equation of state (EOS) parameter, and deceleration parameter—are reconstructed using the extracted best-fit parameters. Our findings show a smooth transition from a decelerating phase (𝑞 > 0) to an accelerating phase (𝑞 < 0), yielding a transition redshift of 𝑧𝑡 = 0.725 for the DESI dataset and 𝑧𝑡 = 0.898 for the joint compilation. Finally, the physical viability of the model is confirmed by verifying the energy conditions, where the Strong Energy Condition (SEC) is characteristically violated at late times, matching experimental limits.

Neutrino oscillations, baryon asymmetry of the Universe and dark matter phenomena can be explained by introducing just three new majorana fermions to the Standard Model. Here we discuss the sterile neutrino dark matter: production mechanisms in the early Universe suggested by minimalistic models, searches by X-ray telescopes of peaks due to neutrino radiative decays, specific impacts on the formation of cosmic large scale structure. Recent studies indicate that the most effective production requires large flavor lepton asymmetries in the primordial plasma which can be accompanied by pion condensate and thus modify the standard picture of the QCD transition.

Neutrino telescopes have become a mature tool for exploring the high-energy Universe. This talk will give a concise overview of the basic principles of neutrino detection at large-volume Cherenkov detectors, their main scientific goals, and the current experimental landscape. Selected recent results from operating neutrino telescopes will be discussed, together with the status of ongoing experiments and plans for the next generation of detectors. Particular attention will be given to the role of neutrino telescopes in identifying cosmic accelerators and in multimessenger studies of the Universe.

Over the past decade, small satellite platforms — especially CubeSat nanosatellites and microsatellites with masses of up to several tens of kilograms — have undergone a profound transformation from educational tools into fully fledged scientific platforms. This shift is particularly pronounced in astrophysics and cosmic-ray physics. Compact detectors based on various types of scintillators coupled with silicon photomultipliers, as well as lightweight silicon microstrip and pixel detectors, are now operating in orbit. Space companies, together with scientists, students, and even schoolchildren, are developing concepts for constellations of satellites carrying small scientific instruments, which enable monitoring of various objects — for example, tracking gamma-ray bursts, observing solar flares and energetic particles, and solving many other problems. This review examines both flown and in-development missions, including GRBAlpha, VZLUSAT-2, GRBBeta, BurstCube, AGILE, NATALIA and others, their scientific goals, technical solutions, and observational results. The analysis shows that small satellites have already provided the detection of about 360 gamma-ray transients, low-latency response to extreme events such as GRB 221009A, and measurements of cosmic-ray flux characteristics. The review concludes by discussing the prospects for next-generation constellations such as COMCUBE-S and argues that small satellites are transitioning from "technology demonstration" to "scientific contribution," becoming indispensable for solving many problems of modern astronomy and astrophysics.

We discuss neural networks for cosmic ray classification at the Carpet-3 experiment. We improve gamma ray sensitivity and obtain new limits on the isotropic diffuse gamma ray flux from Carpet-3 data, improving previously obtained results. We also study the possibility of measuring the cosmic ray mass composition at the knee region at the Carpet-3 experiment, comparing standard reconstruction methods to machine learning analysis. We address the domain shift between Monte Carlo simulations and real-world data by with domain adaptation and study its effects on the neural network performance.

Baikal-GVD is a deep underwater Cherenkov telescope at the bottom of Lake Baikal, built to detect high-energy astrophysical neutrinos. The energy of the neutrino is one of the key parameters of a recorded event, which makes its accurate measurement an important task of the experiment.

We apply transformer neural networks to the reconstruction of the energy of a muon produced by a muon neutrino, in events confined to a single cluster of the telescope. The energy is reconstructed at the point of the muon track where it enters the sensitive volume of that cluster. The input of the network is the sequence of optical module hits recorded in the event, and the network is trained on Monte Carlo simulation.

Training uses unsupervised domain adaptation of the DANN type, which prevents the network from distinguishing simulation from experimental data. The loss function includes a negative log-likelihood term (beta-NLL), so that the network predicts not only the energy but also its own uncertainty for each event. Extension to the joint reconstruction of energy and muon track is planned.

The aim of this work is to forecast the onset time of the second maximum of proton enhancements associated with the transport of particles by solar-wind structures. The "zeroth-order" forecast is based on the kinematic parameters of the solar wind measured at the L1 Lagrange point, and is subsequently refined by machine-learning methods. The difficulty of this problem lies in the nonlinear, non-stationary relationships between proton-flux and solar-wind parameters, on the one hand, and the lack of a training base large enough to build a conventional regression or neural-network model, on the other. We therefore used a quantum regression model, RQNN, in which the input heliophysical parameters are encoded as phase shifts of the wavefunctions of emulated qubits. As an example, consider the prediction of the second maximum in the proton event of 10–11 May 2024, which involved the catch-up (cannibalization) of a slower CME (≈628 km/s, launched on 8 May at 22:24 UT) by a faster one (≈1711 km/s, launched on 9 May at 09:24 UT) at a distance of ≈0.31 AU. Advection of the merged structure to Earth at the OMNI solar-wind speed (684 km/s) predicts the onset of the second proton-flux maximum at about 09:33 UT on 11 May, whereas the actual (GOES-cross-validated ART-XC/Spektr-RG) maximum is observed at 07:33 UT on 11 May, i.e., about 2 hours earlier. RQNN, in turn, predicts the second maximum at 06:58 UT on 11 May, which is about 1 h 25 min (1.4 h) closer to the actual value, reducing the residual from ≈2.0 h to ≈0.6 h.

In order to improve the circulation purification efficiency of the PandaX-xT dark matter detector and efficiently achieve the ultra-trace background required by the detector through flow field optimization, this study conducts CFD numerical simulations of the xenon flow field based on the structure of the PandaX-4T detector. The multi-variable simulation results are introduced into an artificial intelligence (AI) framework, to establish a mapping relationship between the parameters and performance metrics for investigating the flow field characteristics, and completing the structural optimization of the detector. Finally, the flow field simulation is updated based on the optimized parameters. The effectiveness of the optimization scheme in improving flow uniformity and reducing impurity accumulation are analyzed, which could provide guidance and optimization directions for the performance enhancement of large-scale liquid xenon dark matter detectors.

Two main types of ground-based experimental facilities are used to register EAS: atmospheric Cherenkov telescopes and arrays of Cherenkov detectors. The unique TAIGA scientific facility includes both types of installations. The joint analysis of the data coming from these installations should improve the quality of the reconstructed EAS parameters compared to traditional methods that analyze the data separately.

For such a combined multimodal analysis, it is proposed to use a method based on extracting essential features from experimental data using autoencoder type neural networks that do not require pre-marking the data for training. The main advantage of the proposed method over the traditional one is that data from various installations are naturally and easy aggregated at the level of essential features and further analyzed using classical deep neural networks to extract the physical parameters of the EAS.

Using the example of simulated Monte Carlo data for atmospheric Cherenkov telescopes and the Cherenkov detector array HiSCORE of the TAIGA installation, it is shown that this approach allows obtaining the parameters of the EAS in some cases significantly better than traditional analysis methods.

Baikal-GVD neutrino telescope is located in the Southern basin of Lake Baikal with the instrumented depth ranging from 730 to 1275 m. The measured noise rates of the detector channels range from ten to hundreds of kilohertz, depending on season and the depth of the installed photomultiplier. We present an evolution of the method currently employed for muon track event reconstruction in Baikal-GVD. Like in the previous approach, it represents events as graphs, with vertices corresponding to photomultiplier hits and edges corresponding to a causality condition imposed by the Cherenkov cone. However, instead of identifying the vertices of fully connected subgraphs with Cherenkov photons, we use the graph's spectral properties to identify noise hits and provide an initial estimate of the muon direction. This increases collection efficiency for delayed photons from cascades along the track which become dominant at higher energies. The proposed approach provides a 20% increase in Cherenkov hit collection efficiency for an astrophysical neutrino sample and a reduction in processing time, while maintaining a noise rejection rate comparable to that of the previous method.

We present an overview of the deep learning pipeline developed for data processing at the Baikal-GVD experiment. The pipeline covers the complete data analysis chain, from noise hit suppression to the reconstruction of neutrino arrival directions and energies. By capturing spatial and temporal correlations across optical modules, Transformer and Graph Neural Network (GNN) architectures consistently outperform conventional algorithmic reconstruction across all tasks. Furthermore, we discuss architectural enhancements — such as master nodes, fully connected output layers, and loop structures — that boost overall reconstruction performance.

We review applications of large language models in astrophysics and astroparticle physics, including literature retrieval, scientific programming, observational data analysis, and computational experiments. We compare three complementary approaches: domain adaptation, retrieval-augmented generation, and agents that use external tools. Building on this comparison, we propose an architecture for a research assistant for Baikal-GVD and TAIGA. Particular attention is given to GigaChat as a promising foundation for a Russian-language scientific assistant. Its Russian-language specialization and the availability of open weights provide opportunities for adaptation to collaboration documentation and deployment within collaboration computing infrastructure. We propose three pilot use cases: extracting information from astronomical alerts, reproducing a selected analysis, and answering questions about technical documentation. We formulate a protocol for domain-specific evaluation using AstroMLab-1 and collaboration tasks. Integration with scientific tools, computational reproducibility, and validation of physical results are discussed as requirements for developing a GigaChat-based assistant.

A dynamical mechanism for vacuum energy compensation in both de Sitter (dS) and anti-de Sitter (AdS) space-times is discussed. The proposed cosmological model relies on a non-minimal coupling between a scalar field and the curvature scalar. We demonstrate that this mechanism efficiently eliminates huge initial vacuum energies (both positive and negative), dynamically driving the curvature scalar down to zero. In both cases, the universe enters a power-law expansion regime typical for a cosmology dominated by relativistic matter.

Possible corrections to cosmological inflation models based on scalar-tensor gravity are considered. The influence of non-minimal coupling between a scalar field and curvature on cosmological dynamics and parameters of cosmological perturbations is examined, with particular emphasis on corrections arising from a specific parametrization of this coupling.

Cosmological models based on physically motivated scalar field potentials are analyzed for various non-minimal coupling functions, encompassing cases in which the influence of the coupling on both the cosmological dynamics and the evolution of the scalar field is either significant or negligible.

Special attention is devoted to estimating deviations of scalar-tensor gravity models from the Einstein gravity case. These deviations are assessed by applying modern constraints on the parameters of cosmological perturbations. To provide a model-independent analysis of the corrections induced by non-minimal coupling, a classification of inflationary scenarios is introduced. This classification is based on the series expansion of the tensor-to-scalar ratio as a function of the spectral index of scalar perturbations. It is shown that the proposed approach incorporates well-known inflationary models as special cases.

We propose new versions of the slow-roll approximation for inflationary models with nonminimally coupled scalar fields. We derive more precise expressions for the standard slow-roll parameters as functions of the scalar field. To verify the accuracy of the proposed approximations, we consider inflationary models with the induced gravity term and the fourth-order monomial potential. For specific values of the model parameters, this model is the well-known Higgs-driven inflationary model. We investigate the inflationary dynamics in the Jordan frame and come to the conclusion that the proposed versions of the slow-roll approximation are not only more accurate at the end of inflation, but also give essentially more precise estimations for the tensor-to-scalar ratio r and the amplitude of scalar perturbations As.

Ricci–Gauss–Bonnet–Weyl (RGW) gravity, based on a pure geometric Lagrangian defined by a specific combination of the Ricci (R), Gauss–Bonnet (G), and Weyl (W) scalars, is proposed and discussed as a potentially viable generalization of General Relativity (GR) for cosmology, astrophysics, and the Solar System. In this RGW gravity, there are no ghosts or unstable perturbations. Within the Parameterized Post-Newtonian (PPN) formalism, it is shown that RGW gravity has the same PPN parameter values as GR. Without the need for a cosmological constant or dark matter, this RGW gravity agrees well with Solar System data, cosmological data, and the latest data for the scalar spectral index and tensor-to-scalar ratio determined by the evolution of random metric fluctuations during the inflationary stage of the primordial Universe. The physics of the gravitational field arising from RGW gravity is considered in the contexts of all cosmological stages, black holes, supernovae, neutron stars, compact binary systems, galaxy rotation curves, and weak-field gravity. Finally, RGW gravity is discussed in the context of predictions for possible new experiments.

We investigate primordial correlation functions in a broad class of cosmological models within Horndeski gravity whose background evolution admits a controlled slow-roll expansion. Using the Schwinger–Keldysh (in-in) formalism, we derive the primordial three-point correlation functions in the tensor and mixed scalar–tensor sectors, including slow-roll corrections beyond the leading-order approximation. In particular, to the best of our knowledge, our results provide the first general derivation of the mixed scalar–tensor bispectra beyond leading order in the full Horndeski theory. We further obtain the corresponding non-linearity parameters and spectral indices, thereby providing a systematic characterization of primordial non-Gaussianity in this broad class of theories. We also verify the relevant Maldacena consistency relations in the squeezed limits of the mixed correlators. Besides serving as a nontrivial check of the calculations, this verification establishes that the resulting bispectra satisfy the soft-limit constraints implied by residual diffeomorphism invariance and adiabatic single-clock dynamics. As an application, we consider a non-singular cosmological model describing a bouncing Universe and evaluate the associated non-linearity parameters. The resulting predictions connect the primordial dynamics of non-singular cosmology with potentially observable signatures of non-Gaussianity that may be tested by future cosmological observations.

Constructing physically viable models within Horndeski and Beyond Horndeski theories requires strict checks to avoid ghost and gradient instabilities, yet the corresponding stability constraints for dynamical spherically symmetric backgrounds remain incomplete. Previous studies of perturbations over such backgrounds focused exclusively on the odd-parity sector, which yields stability conditions solely for the tensor (gravitational) mode. Consequently, the behavior of the scalar degree of freedom remained unconstrained.

In this work, we address this gap by investigating the even-parity sector of perturbations in both Horndeski and Beyond Horndeski gravity over a general time-dependent, spherically symmetric background. By utilizing the Regge-Wheeler formalism and focusing on monopole ($\ell=0$) perturbations, we isolate the dynamics of the scalar degree of freedom. We successfully integrate out non-dynamical fields and derive the explicit quadratic action for the remaining physical scalar mode.

As a main result, we obtain exact no-ghost and gradient stability conditions, as well as the expression for the radial propagation speed of the scalar mode. These novel constraints strictly limit the scalar sector and complement the previously known tensor-mode conditions from the odd sector. Together, they establish a stringent theoretical framework for the parameter space of Horndeski and Beyond Horndeski theories, which is essential for building physically consistent astrophysical and cosmological models.

Bouncing cosmologies and Galilean Genesis provide alternative scenarios to the standard inflationary paradigm. An important question for such models is whether their characteristic cosmological backgrounds exhibit dynamical attractor behaviour, making their evolution insensitive to a broad class of initial conditions. In this talk, I will discuss the attractor properties of bouncing and Galilean Genesis scenarios and examine the conditions under which the corresponding cosmological solutions can be regarded as dynamically robust.

We develop a manifestly conformal-frame-independent approach to assessing perturbative unitarity and apply it to modified Genesis in a $G_2+G_3$ Horndeski model. The construction uses an effective metric determined by the tensor quadratic action, its associated conformal time, and canonically normalized scalar perturbations. We determine the quadratic coefficients and scalar sound speed, analyze linear stability, and express the scalar cubic action in frame-invariant variables, retaining interactions generated by time-dependent canonical normalization. Power counting identifies potentially restrictive interactions and estimates their characteristic scales relative to the background evolution scale in the asymptotic past.

We then compute the tree-level scalar-exchange contribution to $2 \rightarrow 2$ scattering in a local high-energy approximation. Explicit cancellations among the nominally leading interactions demonstrate the limitations of estimates based on individual operators. The retained leading exchange amplitude contains only the $\ell=0$ and $\ell=2$ partial waves, and we evaluate these projections to estimate the perturbative validity range and its dependence on the scalar sound speed.

As a complementary description of the scalar sector, we derive the cubic Goldstone action for the relevant unitary-gauge effective-field-theory operators on a fixed FLRW background, retaining the time dependence of their coefficients and the interactions generated by restoring time diffeomorphisms.

This work investigates the physical stability of cosmological bounce scenarios. As a starting point, we consider a previously proposed bounce solution for a homogeneous and isotropic background within a subclass of Horndeski theory. In this model, the scalar perturbation mode is non-dynamical ("frozen"), which allows the system to formally evade standard no-go theorems limiting the construction of stable bounces.

In this paper, we investigate the stability of this solution against small spatial inhomogeneities. To this end, we introduce a spherically symmetric dynamical metric and a scalar field with small inhomogeneous perturbations. Based on the derived equations of motion, we verify the stability conditions (i.e., the absence of ghosts and gradient instabilities) using a newly formulated no-go theorem extended to inhomogeneous dynamical metrics.

Our numerical analysis demonstrates that introducing even arbitrarily small spatial inhomogeneities leads to the violation of these stability conditions. We show that the scalar mode, which remains stable and "frozen" in the strictly homogeneous case, acquires dynamics upon deformation of the bounce, inevitably triggering the development of instabilities. Consequently, the mechanism for evading the no-go theorem in a homogeneous background proves to be unstable against spatial fluctuations.

The study of nuclear matter formed in relativistic heavy-ion collisions is one of the key tasks in high-energy physics. In addition to the quark-gluon plasma produced in such colliding systems, the hadron gas phase that represents the final stage of the collision is of particular interest. Investigation of resonance production in relativistic heavy-ion collisions serves as a primary tool for analyzing this hadronic phase. Due to their short lifetimes, resonances act as indicators of the dynamic equilibrium between rescattering and regeneration processes. Furthermore, their production allows for the investigation of a wide range of physical effects, such as the possible restoration of chiral symmetry, strangeness enhancement, baryon anomaly at intermediate transverse momenta, flavor dependence of parton energy loss at high momenta, and others. Currently, the most intriguing region of the QCD matter phase diagram, where the critical point and a first-order phase transition are expected to be discovered, lies within the area of high net-baryon densities and moderate temperatures (at √sNN = 2-15 GeV). The Nuclotron-based Ion Collider fAcility (NICA), a superconducting proton and heavy-ion collider under construction at JINR (Dubna), along with the Multi-Purpose Detector (MPD) experiment, is specifically aimed at exploring this region by studying the nuclear medium formed in relativistic heavy-ion collisions at low temperatures and high net-baryon densities. According to the current schedule, some of the first runs at the NICA accelerator complex will involve xenon nucleus (Xe) collisions with a fixed tungsten (W) target at an incident beam kinetic energy of Ekin = 2.5A GeV. In this work, the feasibility of the MPD detector operating in the fixed-target mode to measure the characteristics of meson resonances was investigated. The study was performed for Xe+W collisions at an energy of 2.5 GeV/nucleon. Since the MPD detector is currently in its preparation phase for commissioning, all processes from the initial nuclear collision to the detector response were reproduced using Monte Carlo simulations. Based on the results of this work, the acceptance regions in rapidity, transverse momentum, and event centrality accessible for physics analysis were determined.

We acknowledge support from Russian Ministry of Education and Science, state assignment for fundamental research (code FSEG-2025-0009)

In 2025, data on $^{16}$O–$^{16}$O and $^{20}$Ne–$^{20}$Ne collisions were collected at the LHC for the first time. Unlike in the LHC runs with $^{208}$Pb beams conducted since 2010, a significant fraction of spectator fragments emitted in collisions of light isospin-symmetric nuclei, such as $^{16}$O and $^{20}$Ne, also have equal numbers of neutrons and protons. Consequently, these fragments exhibit magnetic rigidity similar to that of beam nuclei. As the transverse momenta of spectator fragments are expected to be close to the nominal beam momentum, such $2Z=A$ secondary nuclei may circulate in the LHC. This poses a challenge for tuning the collider beam optics to suppress the circulation of $2Z=A$ fragments, in order to prevent their collisions with beam nuclei and reduce contamination of the $^{16}$O–$^{16}$O and $^{20}$Ne–$^{20}$Ne data due to beam transmutation [1].

The cross sections of production of $^2$H, $^4$He, $^{6}$Li, $^{10}$B, $^{12}$C, and $^{14}$N spectator fragments in $^{16}$O–$^{16}$O were estimated [2] with the Abrasion-Ablation Monte Carlo for Colliders model with pre-equlibrium Minimum Spanning Tree clustering (AAMCC-MST) [3]. While contamination of $^{16}$O–$^{16}$O data is considered negligible based on recently collected data [4], this has not yet confirmed for $^{20}$Ne–$^{20}$Ne collisions.

We report the results of AAMCC-MST modelling of the production of spectator neutrons, protons, as well as $^2$H, $^4$He, $^{6}$Li, $^{10}$B, $^{12}$C, $^{14}$N, $^{16}$O, and $^{18}$F fragments in $^{20}$Ne–$^{20}$Ne collisions at $\sqrt{s_{NN}}=5.36$ TeV. Prior to simulating $^{20}$Ne fragmentation at the LHC, we validated AAMCC-MST using data on fragmentation of $\sim 0.4A$–5$A$ GeV $^{20}$Ne and $^{22}$Ne projectiles in nuclear emulsion and on elemental targets [5,6]. Three density profiles for $^{20}$Ne and $^{22}$Ne were employed: a deformed Woods–Saxon, a five–$\alpha$ bi-pyramidal configuration, and a spherical profile for $^{20}$Ne. Calculations were also performed with and without MST clustering. Comparisons of results obtained with different calculation options demonstrate the sensitivity to both the details of the nuclear structure of $^{20,22}$Ne and the fragmentation modelling.

In all previous studies of neon fragmentation, neither protons nor neutrons were registered. The data on spectator neutrons and protons from $^{20}$Ne–$^{20}$Ne collisions collected by the ALICE Zero Degree Calorimeters (ZDC) [7] will provide a unique opportunity to study fragmentation of isospin-symmetric $^{20}$Ne. Following validation of fragmentation models with these new data, new methods of luminosity monitoring and centrality determination for collisions of light nuclei can be developed with involving both neutron and proton ZDCs.

References

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Momentum distributions of light fragments produced in asymmetric fission in heavy ion collisions provide information on reaction dynamics and breakup mechanisms of spectator systems. At small emission angles relative to the beam direction and with high momentum resolution, energy spectra of light fragments exhibit a double-humped structure contrary to the Gaussian profile expected in usually accepted statistical approach. This effect has been seen in two experiments only [1,2]. This report presents results on the fragmentation of iron nuclei into light fragments at the energy of 230 MeV/nucleon measured in the FRAGM experiment at the TWAC heavy ion accelerator complex [1,3]. It is shown that the measured momentum spectra exhibit this effect and it is most pronounced for protons and tends to diminish for heavier fragments. Furthermore, it is demonstrated that the observation of this effect in both mentioned above experiments can be explained within the framework of certain nucleus-nucleus interaction models which take into account the Coulomb interaction.

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A.T. D’yachenko$^{1,2}$

$^1$B.P. Konstantinov Petersburg Nuclear Physics Institute, National Research Center "Kurchatov Institute", Gatchina, Russia

$^2$Emperor Alexander I Petersburg State Transport University, St. Petersburg, Russia

Based on the effective Klein–Fock–Gordon equation [1], a description is given of the emission of cumulative protons, pions, and fragments (p, π, K, d, t) in heavy-ion collisions at energies of the U-70 accelerator (IHEP, Protvino) [2,3], КI (Moscow) [4,5], and the BM@N collaboration (JINR, Dubna) [6-8]. The advantage of this approach in describing the experimental data of IHEP and KI for the emission of protons, pions, kaons, and fragments of H, $^2$H, $^3$H, $^3$He, $^4$He, $^6$Li, $^7$Li, compared to other theoretical models, is shown.

An explanation for the splitting effect in the momentum spectra of protons and light fragments in the (230 MeV/A)$^{56}$Fe+$^9$Be→f+X reaction in the FRAGM (KI) experiment [9] is provided. This splitting is explained by the nucleon potential, which depends quadratically on the distance from the particle emission center. The spectrum splitting disappears with increasing ion collision energy and upon transition to heavier fragments.

When describing the available experimental data, it is essential to identify the resulting hot spot, which is compatible with the hydrodynamic model of hot jet separation in heavy-ion collisions [10], and which has recently been developed in elementary particle physics [11].

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The Multi-Purpose Detector (MPD) at the NICA complex in Dubna is designed to investigate the strongly interacting matter in the vicinity of the QCD critical point. The properties of the medium created in heavy-ion collisions can be determined from the analysis of the hadron spectra. We present reconstructed invariant transverse-momentum spectra of the light hadrons ($\pi^\pm$, $K^\pm$, $p$) produced in simulated Xe+W collisions at $E_{kin}$ = 2.5 GeV in the fixed-target mode of the MPD experiment. A good agreement between the reconstructed and generated data is observed. Preliminary estimates of the medium parameters can obtained from a simultaneous Blast-Wave fit to the spectra of positively charged particles.

Hadron transverse momentum ($p_{T}$) spectra serve as a sensitive probe of matter produced in relativistic nuclear collisions, with statistical frameworks being widely used to extract its thermodynamic parameters. Despite extensive research into particle production across a wide range of collision energies, of particular interest is a detailed analysis of $p_{T}$ spectra under the conditions of the Spin Physics Detector (SPD) experiment at the NICA collider. To address this, the current study presents generator-level results on hadron $p_{T}$ spectra in O+O, Kr+Kr, and Xe+Xe collisions at $\sqrt{s_{NN}} = 6$ GeV. Events are simulated using two transport approaches: the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) and the Simulating Many Accelerating Strongly-interacting Hadrons (SMASH) models. The calculated $p_{T}$ distributions are analyzed within the framework of non-extensive Tsallis statistics. The phenomenological Tsallis distribution is fitted to the charged hadron spectra from both generators. Furthermore, the analysis of the UrQMD events is extended to include identified hadron spectra, for which the fit is performed using the exact $p_{T}$ distribution of the Tsallis-3 statistics. The study provides a comparison of the results on charged hadron spectra between the UrQMD and SMASH models. The dependence of the extracted parameters on centrality and system size is presented for both charged and identified hadrons. For the identified particles, the parameters are further examined across different species. The obtained results may be relevant for future experimental measurements at the NICA collider.

The search for extreme states associated with changes in the phase of nuclear matter is one of the key tasks of high-energy heavy-ion physics. It is known that systems exhibit fractal behavior near phase transitions. The fractality (intermittency) of identified charged hadrons in the pseudorapidity range |η| < 0.5 and the transverse momentum range 0.2 < pT < 2.0 GeV/c was studied in the STAR experiment at RHIC in Au+Au interactions at energies √sNN = 7.7-200 GeV [1]. In the present work, the effect of the string melting scenario on the characteristics of fractal and non-fractal events is studied. Au+Au events at the energy √sNN = 200 GeV were obtained by using a Multi-Phase Transport (AMPT) generator [2,3]. Events of several centrality classes (0–5%, 5–10%, 10–20%, and 30–40%) were analyzed. An event-by-event fractal analysis carried out by using the SePaC method [4-7] allowed us to divide the events into fractal and non-fractal ones. It was established that the pT-spectrum of fractal events has a kink, whereas that of non-fractal events is fitted with an exponent at pT > 2.0 GeV/c. The slope of the non-fractal pT-spectra depends on the string melting scenario. The kink position of the fractal pT-spectra and the behavior of the fractal dimension (DF) spectra depend on the event centrality. The established patterns are applicable for comparison with experimental data.

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We present a comparison of Monte Carlo modified Glauber model predictions with recent measurements of the centrality dependence of total charged-particle yields in ¹⁶O+¹⁶O and ²⁰Ne+²⁰Ne collisions at the LHC. The model extends the Standard Glauber approach by introducing a single parameter, k, the mean fractional momentum loss per inelastic nucleon-nucleon collision due to multiparticle production; this reduces the inelastic cross section and multiplicity in subsequent nucleon collisions. The parameter k was fixed from the previously successful description of the non-linear centrality dependence of charged-particle yields measured by ALICE in Pb+Pb collisions, and the resulting predictions are confronted here with the newly available data for the light collision systems.

The authors acknowledge Saint-Petersburg State University for a research project ID: 153212394

We present an extended analysis of the transverse energy density ⟨dE_T/dy⟩ at midratpiidty and relevant values of multiplicity density ⟨dN/dy⟩ and mean transverse momenta ⟨p_T⟩ for identified strange particles produced in the most central A+A collisions at high energies. The study is based on published experimental data on transverse momentum distributions and particle yields obtained in Au+Au, Pb+Pb, and Xe+Xe collisions in the energy range √(S_NN) from 39 GeV to 5.44 TeV .
Particular attention is paid to the quantities entering the calculation of ⟨dE_T/dy⟩: the particle rapidity density ⟨dN/dy⟩ and the mean transverse momentum ⟨p_T⟩ measured at midrapidity . We investigate their dependence on the collision energy √(S_NN ) for different strange-particle species and compare the power-law fits of the corresponding excitation functions.
The obtained energy dependences of ⟨dN/dy⟩, ⟨p_T⟩, and ⟨dE_T/dy⟩ are analyzed to test the hypothesis of a common production mechanism for particles with different strange-quark content. The results are discussed within the Multipomeron exchange model and the Bjorken approach to energy density estimation in relativistic heavy-ion collisions.
The authors acknowledge Saint-Petersburg State University for a research project ID: 153212394

The Multi-Purpose Detector (MPD) experiment is a flagship heavy-ion experiment of the NICA facility at JINR, Dubna, currently under commissioning. The experiment will operate in the energy range $\sqrt{s_{NN}}$ = 4-11 GeV in collider mode and $\sqrt{s_{NN}}$ = 2.4-3.5 GeV in fixed-target mode, together covering the high net-baryon density region of the QCD phase diagram. Dielectron measurements in heavy-ion collisions probe the temperature of the fireball as well as in-medium modification of the vector meson spectral function.

The MPD experiment offers excellent track reconstruction and electron identification capabilities, making it well suited for the measurements of dielectrons. In this presentation, after briefly reporting the current status of the NICA facility and the MPD experiment, we present the dielectron analysis methodology developed for the MPD experiment as established and validated in the collider-mode. We will further present preliminary performance results of MPD in dielectron measurements in the fixed-target configuration.

The program is aimed at the experimental search for and study of new phenomena and the development of new approaches to solving pressing problems of relativistic nuclear physics, such as the issues of deconfinement and phase transition at low temperatures and high densities, the properties of diquarks, light exotic states, and polarization anomalies at large transverse momenta. To address these problems, it is planned to create a multi-purpose facility at the extracted beams of the Nuclotron, capable of operating at the maximum achievable intensities of extracted proton and light-nucleus beams. An intense proton or light-nucleus beam and a large acceptance will make it possible to study rare processes in which at least one of the secondary particles has the maximum transverse momentum achievable at Nuclotron energies. In such interactions, it is intended to perform, alongside with inclusive measurements, correlation (including femtoscopy) and exclusive measurements. The organization of a staged development of the program is considered, from preliminary experiments and techniques development to a full-scale facility with a large acceptance.

The second Short-Range Correlations (SRC) experiment at JINR, performed in 2022, used a 44.8 GeV/c $^{12}C$ beam incident on a liquid-hydrogen target to study hard proton knockout from $^{12}C$ in inverse kinematics. The reaction products were detected with a modified BM@N spectrometer. The experimental setup was optimized for proton–proton scattering near $90^{\circ}$ in the center-of-mass frame, corresponding to a squared four-momentum transfer of approximately 2.5 $GeV/c^2$.

Under these kinematic conditions, the cross section for the $^{12}C(p,2p)^{11}B$ reaction was measured for the first time. The result was compared with single-particle distorted-wave impulse-approximation calculations incorporating well-constrained initial- and final-state interactions within the Glauber framework. The extracted spectroscopic reduction factor, R_s=0.96±0.01(stat.) ±0.05(syst.), is consistent with results from high- $Q^2$ A(e,e'p) measurements. It is, however, significantly larger than the reduced single-particle strengths, R_s=0.6, typically obtained from low-energy quasi-elastic electron- and hadron-induced reactions. This comparison supports a scale-dependent picture of the observed single-particle strength in nuclei.

The ongoing analysis of events with an identified $^{10}B$ residual nucleus searches for exclusive signatures of scattering from short-range-correlated nucleon pairs in $^{12}C$. The event selection is guided by detailed simulations of the SRC signal and relevant background processes. The talk will present the measured quasi-elastic cross section and spectroscopic strength, discuss the observed exclusive event topologies, and report the current status of the SRC-pair knockout analysis.

The reaction np → Δ-Δ ++ was studied at incident neutron momenta P0 = 3.83 and 5.20 GeV/c. The reaction cross‑sections were calculated. It has been shown that to describe the spin density matrix [ρij], it is necessary to take into account the ρ‑meson exchange diagram. The obtained results are compared with data from other experiments.

The experiment on photodisintegration of tensor polarized deuteron is in progress. It is carried out at VEPP-3 storage ring using the internal polarized gas target technique. The component T20 of the tensor analyzing power is obtained by measuring the target polarization asymmetry in the photon energy range 400–640 MeV. The energy of photons is defined by the system that tags nearly real photons developed at the Budker Institute of Nuclear Physics (BINP).

We discuss the results of measuring the tensor polarization of a deuterium gas target during an experiment at the VEPP-3.

Spin resonances in an accelerator can significantly affect the polarization of the particle beam during the acceleration cycle. To monitor the evolution of polarization and to understand the acceleration dynamics in real time, a reliable polarimeter is essential. DSS polarimeter at the Nuclotron Internal Target Station is a suitable instrumentation for this purpose. Its performance and efficiency were evaluated for $pp$-elastic scattering through comprehensive Monte-Carlo simulations using the Pluto event generator in the vicinity of the integer resonance $\gamma \text{G} = 3$. The results confirm that the existing polarimeter can provide valuable diagnostic information with acceptable efficiency over a significant energy range of about 100 MeV.

Interpretation of the spin observables in nuclear collisions data require spin dependent nucleon scattering ($pp$ and $pn$) amplitudes. These quantities can be extracted from the asymmetries in the polarized $pd$ collisions. At the SPD, although the asymmetric $pd$ collisions are unlikely, the desired quantities can still be accessed via the quasi-elastic scattering $dd \rightarrow npd$ from the collisions of polarized deuteron beams. It has been proven [1] that the asymmetries measured from polarized $dd$ process, under the S-wave Impulse Approximation, are directly related to the relevant counterparts from the desired $pd$ process. This work used an event generator based on unpolarized Glauber cross-sections and Geant4 detector simulation to study the feasibility and statistical accuracy of measurements of the relevant vector and tensor polarized asymmetries like $A_y, A_{yy}, C_{y,y}, C_{yy,y}$ at the SPD during the first stage of operations.

[1] Y. N. Uzikov, Phys. Part. Nucl. Lett. 22, no.6, 1392-1397 (2025)

This study addresses the design and prototyping of the Beam-Beam Counter (BBC) subsystem for the SPD experiment. The proposed prototype features a modular structure of 16 sectors, with a total number of tiles equal to 128, as well as a dedicated configuration for integration into the Phase 0 of SPD experimental setup. To validate its performance, two reduced sectors were tested in fixed-target mode using 124Xe+Ag collisions at 2.2 GeV/nucleon on the internal target station (ITS) of the Nuclotron. The full DAQ chain based on the FERS5200 system was successfully validated under operational beam conditions both in triggered and triggerless modes. These results establish a critical benchmark for the commissioning of the proposed prototype and are directly relevant to upcoming Phase 0 measurements of the SPD/NICA project.

A simulation of the performance of the SPD BBC detectors for dd collisions at energies up to √s_NN = 13.5 GeV is presented. The results are compared for the following event generators/models: Geant4 FTF, PYTHIA 8.3, UrQMD, and DCM. Contributions from both elastic and inelastic processes are considered, and the possibility of selecting dd – elastic and dp – quasi-elastic scattering events using the Beam-Beam Counters is discussed.

The angular distributions of Drell-Yan lepton pairs allow to determine precisely the dynamics of vector boson production in quantum chromodynamics. The dependence of the angular coefficients on the transverse momentum of the $J/\psi$ meson was obtained at the energy of the second stage of the SPD experiment using the Pythia generator. The $J/\psi$ mesons produced in $pp$ collisions at $\sqrt{s_{NN}} = 27$ GeV and decaying into a pair of muons were used in the analysis. Machine learning (ML) methods were applied for the selection of decay muons.

The COHERENT collaboration is devoted to study of the Coherent Elastic
Neutrino-Nucleus Scattering (CEνNS) using the high-quality pion-decay-at-rest neutrino
source at the Spallation Neutron Source located in the Oak Ridge National Laboratory.
The CEvNS process is predicted in the Standard Model and it dominates in low-energy
neutrinos interactions with matter. Its measurement provides a Standard Model test and
is important for supernova explosion studies as well as for prediction of the background
floor for dark matter direct detection.
The COHERENT effort is a broad program of diverse experiments related to CEvNS
studies including neutrino cross-sections measurements, nuclear recoil quenching factor
evaluations and neutrino flux measurement. Several detectors of various types are
installed at SNS to cover a broad range of nuclei. The most prominent detectors are:
CsI[Na], liquid Ar, NaI[Tl], HPGe, D2O. The CEvNS signal was clearly observed in
several detectors, the results agree well with the SM prediction. This talk provides an
overview of the actual program, current results and future prospects for the
COHERENT.

The PandaX experiment at the China Jinping Underground Laboratory (CJPL) uses large-scale liquid-xenon time projection chambers to search for dark matter and other rare physical processes. PandaX-4T, with a multi-tonne xenon target, has accumulated extensive science data and established competitive constraints on WIMP dark matter, while significantly extending its physics program toward light dark matter, exotic dark-sector interactions, solar neutrinos, and double-beta decay. In this talk, I will present an overview of the current status and recent physics results of PandaX-4T, highlighting the broad discovery potential enabled by its low-background environment and wide energy coverage. I will also discuss the future PandaX program. Building on the experience of PandaX-4T, the collaboration is preparing for the PandaX-40T phase, which will substantially increase the xenon target mass and further improve sensitivity to dark matter interactions toward the neutrino-fog regime. At the same time, the enlarged detector will provide powerful opportunities for neutrino physics and searches for other rare processes, establishing PandaX as a general-purpose underground observatory for particle physics and astrophysics.

The νGeN experiment is aimed to study reactor antineutrinos properties at Kalinin Nuclear Power Plant in Udomlya. The experimental setup is located at about 11 meters under 3.1 GWth reactor which is leading to an antineutrino flux of (3.9-4.4)*10$^{13}$ cm$^{-2}$ s$^{-1}$. To detect antineutrinos the low-background 1.4 kg HPGe detector with energy threshold less than 300 eV is used. Such a threshold and high antineutrino flux gives a possibility to detect coherent elastic scattering of reactor antineutrinos on Ge nuclei in the fully coherence regime as well as search for the anomalous neutrino electromagnetic properties. The current status of the measurement and the planned upgrade of the setup will be presented.

We present the results of the first search of reactor antineutrino capture on $^{72}$Ge with the metastable $^{72m}$Ga ($T_{1/2}$ = 39.7 ms, $E_{γ}$ = 119.7 keV) in the final state. The search is performed based on ~800 kg·days of data acquired by the νGeN 1.41-kg germanium spectrometer at the Kalinin nuclear power plant. An upper limit on exclusive $^{72}$Ge($\bar{ν}$, $e^+$)$^{72m}$Ga cross section is evaluated.

After an introduction to the theory of neutrino electromagnetic properties [1,2,3] and a discussion of existing experimental constraints on the magnetic moments of neutrinos and other electromagnetic characteristics obtained in ground-based experiments (including the latest estimates from XENONnT [4] and LUX-ZEPELIN [5]) and results from astrophysical observations [6,7], we present the new SATURNE experiment, which is being implemented in the National Center for Physics and Mathematics in Sarov [8,9,10]. The goal of the SATURNE project is to detect for the first time the coherent elastic scattering of tritium antineutrinos on liquid helium target atoms in the superfluid state, which will allow to obtain new upper limits (or to measure) the value of the neutrino magnetic moment on the scales. At the first stage of the implementation of the SATURNE project, it is also planned to use a low-temperature scintillation and a cryogenic silicon antineutrino detectors.

[1] C.Guinti, A.Studenikin, Neutrino electromagnetic interactions: A window to new physics, Rev. Mod. Phys. 87 (2015) 531.
[2] C.Giunti, A.Kouzakov, Y.F.Li, A.Studenikin, Neutrino electromagnetic properties, Annu. Rev. Nucl. Part. Sci. 2025, 75: 1–29.
[3] A.Studenikin, Electromagnetic neutrinos: The basic interaction processes and constraints from laboratory experiments and astrophysics, Int. J. of Mod. Phys. E 33 (2024) 2441033.
[4] A.Khan, Light new physics and neutrino electromagnetic interactions in XENONnT, Phys. Lett. B 837 (2023) 137650.
[5] M.Atzori Corona et al., New constraint on neutrino magnetic moment from LZ dark matter search results, Phys. Rev. D 107 (2023) 053001.
[6] S.Jana and Y.Porto, Resonances of supernova neutrinos in twisting magnetic fields,
Phys. Rev. Lett. 132 (2024) 101005.
[7] V. Brdar, A. de Gouvˆea., Y.-Y. Li, P. Machado, Neutrino magnetic moment portal
and supernovae: New constraints and multimessenger opportunities, Phys. Rev. D 107
(2023) 073005.
[8] M.Cadeddu, F.Dordei, C.Giunti, K.Kouzakov, E.Picciau, A.Studenikin, Potentialities of a low-energy detector based on 4He evaporation to observe atomic effects in coherent neutrino scattering and physics perspectives, Phys. Rev. D 100 (2019) 073014.
[9] G.Donchenko, K.Kouzakov, A.Studenikin, Elastic neutrino–atom scattering as a probe of neutrino millicharge and magnetic moment, JETP Lett. 117 (2023) 879.
[10] M.Cadeddu, F.Dordei, C.Giunti, A. Ivashkin, K.Kouzakov, F.Lazarev, O. Moskalev, I.Stepantsov, A.Studenikin, I.Tkachev, V.Trofimov, M.Verkhovtsev, M.Vyalkov,
A.Yukhimchuk, E.Zagirdinova, SATURNE: The Sarov Tritium Neutrino Experiment for probing coherent elastic neutrino-atom scattering and neutrino electromagnetic interactions, Springer Proc.Phys. 425 (2025) 99.

Superfluid helium-4 (He-II) is being considered as a detector material for light dark matter searches [1,2] and the observation of coherent elastic neutrino-atom scattering (CE$\nu$AS) [3]. It has extreme intrinsic radiopurity, high impedance to external vibration noise, and a unique quantum evaporation signal channel enabling the detection of phonon- and rotonlike modes via liberation of He-4 atoms into a vacuum. Detecting the liberated atoms using atomic adsorption onto a calorimeter suspended in vacuum above the free surface of the target He-II, in principle, can make it possible to measure unprecedentedly low recoil energies (on a meV scale).

In this contribution we address the issue of the He-II response to low-energy elastic neutrino-atom scattering. Specifically, we focus on how the effects of the real medium alter the atomic recoil spectra calculated in the simplified model of ideal Bose-Einstein condensate (BEC) for He-II. We present calculations for scattering of tritium electron antineutrinos on atoms in He-II, which case is relevant to the SArov Tritium-Ultra-Rich Neutrino Experiment (SATURNE) [4] that aims at the first ever observation of CE$\nu$AS and the search of neutrino magnetic moment with a world-leading sensitivity. We show that taking into account the realistic atomic momentum distribution in He-II [5] leads to quantitative and qualitative differences with respect to the ideal BEC model. We outline the risks to misinterpret the future SATURNE data as a signal of new physics, in particular, such as the neutrino magnetic moment, if ignoring the effects of the real He-II medium.

[1] S. A. Hertel, A. Biekert, J. Lin, V. Velan, and D. N. McKinsey, Phys. Rev. D 100, 092007 (2019)

[2] B. von Krosigk et al., SciPost Phys. Proc. 12, 016 (2023)

[3] M. Cadeddu, F. Dordei, C. Giunti, K. A. Kouzakov, E. Picciau, and A. I. Studenikin, Phys. Rev. D 100, 073014 (2019)

[4] K. A. Kouzakov, I. S. Stepantsov, and A. I. Studenikin, Phys. Atom. Nucl. 88, 275 (2025)

[5] P.E. Sokol and W.M. Snow, in Excitations in Two-Dimensional and Three-Dimensional Quantum Fluids, ed. by A.G.F. Wyatt and H.J. Lauter (Plenum Press, New York, 1991), p. 47

An analysis of the most recent, most precise experimental data on neutron decay points to the need to extend the Standard Model by introducing an admixture of the right-handed vector boson $W_R$. A left-right asymmetric weak interaction model is presented, in which the sign of the mixing angle of $W_R$ and $W_L$ reverses upon the transition from $W^-$ to $W^+$. In this model, CP violation arises due to the presence of an admixture of the right-handed vector boson. The model parameter, the mixing angle $\zeta = -(2.7 \pm 0.9) \cdot 10^{-3}$, is derived from neutron decay — the lifetime and decay asymmetries — as well as from studies of proton decay in nuclei, the so-called superallowed $0^+$-$0^+$ transitions. The $W_R$: mass $M_{W_R} = (340 \pm 60)$ GeV estimate is given by the relation from the parameter $\delta = -(5.5\pm1.8) \cdot 10^{-2}$, which is the ratio of the squares of the mass states of vector bosons. It is shown that within the framework of this model, the effects of CP violation in the decays of $K^0$-mesons, $D^0$-mesons, $B^0$-mesons, and $B^0_S$-mesons can be successfully described.

The formation of the Universe's baryon and lepton asymmetries is examined within the framework of a left-right asymmetric model of weak interaction. The presence of a right-handed vector boson admixture—with mixing angles of opposite signs for $W^-$ and $W^+$—results in differing lifetimes for neutrons and antineutrons, which decay via $W^-$ and $W^+$, respectively. This difference gives rise to baryon asymmetry during the hadronization of quark-gluon plasma at temperatures below 150 MeV. The formation of lepton asymmetry in the left-right model is linked to the presence of sterile (right-handed) neutrinos; these do not thermalize and instead escape the cosmic plasma, carrying away a lepton asymmetry that is opposite in sign to the baryon asymmetry. Overall, a baryon-lepton asymmetry emerges while the difference between baryon and lepton numbers ($B-L$) is conserved. The potential for enhancing the experimental precision of neutron decay asymmetry measurements is noted as a means to increase the confidence level in substantiating the left-right asymmetric model of weak interaction.

Results of measurements of Higgs boson production cross section via the vector-boson-fusion mechanism (VBF) at the LHC are reviewed. Perspectives of such measurements at the high-luminosity LHC as well as at possible future electron-positron, hadron and muon colliders are discussed.

This report presents the latest results and analysis strategy for the search for Higgs boson decays into dark matter (DM) particles using data collected during Runs 1 and 2 of the Large Hadron Collider (LHC). The search is interpreted within Higgs-portal models, in which the Higgs boson provides a connection between the Standard Model and the dark sector. Upper limits on the Higgs boson branching fraction to invisible final states are derived at a 95% confidence level, assuming the Standard Model Higgs boson production cross section. The obtained limits represent the most stringent constraints from the ATLAS and CMS experiments at the LHC to date. These values from the ATLAS experiment are compared with the results of direct search experiments.

The prospects for extending the ATLAS search using data collected during the initial period of LHC Run 3 are also discussed, with particular emphasis on the expected sensitivity to invisible Higgs boson decays.

A study of $Z$-boson pair production at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV is presented. The analysis uses $140~\text{fb}^{-1}$ of proton--proton collision data collected with the ATLAS detector. Both inclusive $ZZ$ production and $ZZ$ production in association with two jets ($ZZjj$) are considered. The final state is defined by one $Z$ boson decaying into a pair of charged leptons and the other into a pair of neutrinos. Fiducial cross sections are measured for the $ZZ$ and $ZZjj$ production processes. Differential cross sections are also measured for a wide range of kinematic observables. In addition, the inclusive $ZZ$ cross section is extrapolated to the full phase space for $Z$ bosons in the mass range 66--116 GeV. The results are found to be in good agreement with Standard Model predictions.

Data provided by the LHC enable searches for a variety of new particles, but no deviations from the SM have been found. Therefore, these studies are supplemented by indirect searches for new physics in the same data, assuming that new particles are inaccessible. Anomalous quartic gauge couplings can arise in diverse physics models; limits on the coupling parameters are related to constraints on new physics model. Searches for these coupling manifestations have been carried out in different final states using data collected by the ATLAS detector in 2015-2018. This report presents the results of the combination of various analyses of vector-boson scattering and a triboson study. This work is not only the first combination, but also the most comprehensive study of anomalous quartic gauge couplings. It provides confidence intervals for scenarios with one or two non-zero parameters at a time as well as a treatment of theory unitarity and positivity bounds. Confidence limits with all coupling parameters being non-zero simultaneously are also set.

Using an up-to-date compilation of $\sigma_{\mathrm{tot}}(e^+e^- \to hadrons)$ data we estimated the LO hadronic contribution $a_\mu^{LO\, HVP}$ to the muon anomalous magnetic moment $a_\mu$. Incompatibilities between $\sigma_{\mathrm{tot}}(e^+e^- \to hadrons)$ measurements by independent experiments are mitigated by extra systematic uncertainties estimated using as a guideline a requirement of uniformity of $\chi^2$ distribution over degrees of freedom in joint fits of $\sigma_{\mathrm{tot}}$. Tensions in the $e^+e^-$ input data translate into an expanded uncertainty of the $a_\mu^{LO\, HVP} = (697.7 \pm {9.8}_{e^+e^-} \pm 3.6_{sys}) \times 10^{-10}$. Given this, we obtain $a_\mu^{\mathrm{SM}} = 11659185.5(10.6) \times 10^{-10}$, below the experimental world average $a_\mu^{\mathrm{exp}}$ at $2\sigma$ level.

Some extensions of the Standard Model (SM) predict the existence of fermions with an electric charge much smaller than that of the elementary charge. Such particles, known as millicharged particles (MCP), may be produced in nuclear reactors from the interactions between gamma-rays and the electrons of reactor materials. In this work, the MCP flux and energy deposition distributions at Kalinin Nuclear Power Plant (KNPP) are presented. The considered experiments, RED-100 (with a two-phase emission detector filled with either xenon or argon) and νGeN (with a solid-state germanium detector) were in exposition at KNPP. The proximity of these experiments to high intensity flux of reactor gamma quanta allows for the probe of the MCPs by comparing reactor-ON (active reactor) and OFF (reactor shutdown) data. The expected count rates of MCP interaction with electrons of the sensitive volumes of the aforementioned detectors are further combined with measured background levels to asses the sensitivity of the experiments to hypothetical reactor-produced MCPs.

The measurement of the Higgs boson parameters constitutes a significant part of the CEPC program. This work is devoted to studying the process e-e+->ZH at sqrt(s) = 240 GeV with all-hadronic, four-jet final states. The CEPC detector fast simulation and event reconstruction using the Delphes package have been performed for the signal and different background processes. A novel approach to four-jet final state analysis has been implemented, which allows better reconstruction of boson mass by combining information from dijet invariant mass and recoil mass to another dijet. The cut-based approach was applied to reject leptonic and semileptonic backgrounds. For effective suppression of the four-jet background, a Transformer-based classifier was trained using the PyTorch framework for binary classification on the mixed dataset before or after kinematic cuts. Different combinations of signal efficiencies and purities are considered and their impact on the accuracy of Higgs boson mass measurement is estimated.

In different analyses of higgsstrahlung process at CEPC, the final states with leptons from Z boson decays provide a very clean environment for studies of Higgs boson parameters. While the channel $Z\rightarrow \mu^+ \mu^-$ is the most precise, the channel $Z\rightarrow e^+e^-$ suffers from final state radiation losses. In the proposed CEPC detector designed for the application of Particle Flow approach, momenta of charged particles are reconstructed from the tracker, while an energy of gammas $-$ from the electromagnetic calorimeter. In this study, the impact of electromagnetic calorimeter resolution on the correction for final state radiation is estimated. It is demonstrated that the correction of electron energy for final state radiation in the CEPC detector can improve the boson mass resolution by about a factor of two and make it comparable with that without radiation.

Tetraquarks containing two bottom quarks are studied in the framework of the relativistic quark model based on the quasipotential approach and QCD. The tetraquark is considered as a bound state of a diquark and an antidiquark. The interaction quasipotential includes both spin-dependent and spin-independent relativistic contributions. The finite size of the diquark is explicitly taken into account. The obtained tetraquark masses are compared with the thresholds of strong fall-apart decays into two mesons. States that may appear as narrow resonances in suppressed decay channels are identified.

We investigate strong and radiative decays of low-lying conventional charmonium and exotic charmonium-like states, recently reported by the Belle-II and BES-III Collaborations, within the covariant confined quark model.
A unified description of $S$- and $P$-wave radiative transitions of six charmonium states ($\eta_c$, $J/\psi$, $\chi_{cJ}$, $h_c$) is given with a single parameter $\varrho$. The value of $\Gamma(J/\psi\to\gamma\eta_c)$ is predicted, and the transition $h_c\to\gamma\eta_c$ is calculated for the first time, yielding an indirect estimate of $\Gamma_{\text{tot}}(h_c)$. The deconfinement limit $\lambda\to0$ confirms the stability and internal consistency of the approach.
Three-particle strong decays of exotic states are described through intermediate scalar resonances for the first time, with the broad $f_0(500)\to\pi^+\pi^-$ dominating over the narrow $f_0(980)$; a modified Breit-Wigner function significantly reduces $\Gamma(Y\to K^+K^-J/\psi)$, and for $Y(4230)$ the theoretical ratio of $K^+K^-J/\psi$ to $\pi^+\pi^-J/\psi$ agrees with BESIII data.
Isospin violation in hidden-charm strong decays of $X_2(4014)$ is studied, treating it as a molecular four-quark state. The calculated partial widths for $\omega J/\psi$ and $\rho^0 J/\psi$ agree with recent data. The predicted ratio $\mathrm{BR}_{X_2}\approx1.14$ is insensitive to mass deviations and free of threshold singularities, providing an experimentally testable criterion for a molecular (tetraquark) interpretation.

\vspace*{5mm}
Refs:

Gurjav Ganbold \textit{et al.}, Phys. Rev. D \textbf{104}, 094048 (2021).

Gurjav Ganbold and M. A. Ivanov, Eur. Phys. J. A 60, 13 (2024).

Gurjav Ganbold and M. A. Ivanov, Phys. Rev. D \textbf{111}, 014007 (2025). \

Recently the number of experimentally observed Υ mesons significantly increased. This opens the possibility to observe their weak decays. In this talk semi- and non-leptonic Υ decays are studied within the framework of the relativistic quark model based on the quasipotential approach and quantum chromodynamics. The form factors are obtained and their dependence on the square of the transferred momentum is explicitly determined in the accessible kinematic range. On the basis of these form factors and factorization approximation, semi- and non-leptonic decay rates of the Υ mesons are calculated. The detailed comparison with other theoretical results is given.

$BB$ pairs from $\Upsilon(4S)\to BB$ decays are in $C$-odd state. However, there is a small admixture of the $C$-even state and it modifies the time dependent $CP$-asymmetry. The $C$-even component appears due to soft photon emission, breaking the pure $C$-odd nature of the initial state. Using the two-particle wave function formalism, we derive analytical expressions for $CP$-asymmetry in both pure and mixed $C$-parity states. We emphasize the strong energy dependence of the admixture magnitude.

We revisit the decays $B^- \to \ell^+ \ell^- \bar{\nu}_{\ell'} \ell'^-$ in both $\ell \neq \ell'$ and $\ell = \ell'$ cases. Compared to our previous works, new contributions to decay parameters are investigated. Non-zero lepton masses and interference terms are fully taken into account. Excited resonances are included. The calculations are performed using the orthogonal amplitudes technique. Updated theoretical predictions for branching ratios and differential distributions are presented.

Neutrino oscillations probe quantum coherence over macroscopic distances and are therefore sensitive to possible environmental and beyond-Standard-Model effects. While neutrino decoherence is often introduced phenomenologically through Lindblad-type equations, its microscopic origin requires a consistent quantum field-theoretic treatment.

We present an open-system framework for neutrino propagation in which generalized master equations for the neutrino density matrix are derived from neutrino interactions with external degrees of freedom. The formalism incorporates momentum-changing transitions and reproduces the standard Lindblad equation in suitable limits. We consider three mechanisms of neutrino quantum decoherence: neutrino decay, elastic scattering in a medium, and propagation in a fluctuating classical axion-like-particle field. For neutrino decay, the dissipative terms are related to decay and inverse-decay widths, allowing phenomenological decoherence bounds to be translated into constraints on neutrino lifetimes. For elastic scattering, the framework describes decoherence, quantum-Zeno-like suppression of oscillations, and possible effects of non-standard interactions or dark-sector particles.

The talk is based on our recent results

[1] K.Stankevich, A.Studenikin, M.Vyalkov, Quantum field-theoretic framework for neutrino decoherence from scattering in a medium, Phys.Rev.D 114 (2026) 4.
[2] A.Lichkunov, K.Stankevich, A.Studenikin, Neutrino quantum decoherence in a fluctuating ALPs field, Phys.Rev.D 112 (2025) 12.
[3] K.Stankevich, A.Studenikin, M.Vyalkov, Generalized Lindblad master equation for neutrino evolution, Phys.Rev.D 111 (2025) 3.

The standard paradigm of neutrino oscillations assumes that neutrinos propagate as a coherent superposition of mass eigenstates. However, in a number
of physical scenarios — including wave packet spreading, quantum gravity effects, spacetime fluctuations, or interactions with a hot or dense medium —
this coherence can be violated, leading to the phenomenon of neutrino decoherence. Decoherence manifests itself as an exponential damping of the interference
terms in the oscillation probability and, consequently, can modify predictions
for oscillation experiments. Searches for such effects are actively pursued using
data from reactor experiments (KamLAND, Daya Bay, RENO) and accelerator experiments (MINOS/MINOS+, T2K, NOvA), and are also part of the
physics programme of future facilities such as JUNO and DUNE. The theoretical description of decoherence naturally fits within the open quantum systems
framework, where neutrinos are treated as a subsystem interacting with a quantum environment.

In this work, the open quantum systems formalism is applied to the dynamics
of neutrinos in a thermal bath of bosons at finite temperature. Within the
Markov and secular approximations, a reduced kinetic equation for the neutrino
density matrix is derived from the von Neumann equation for the total ”neutrino
+ environment” system, yielding a Lindblad-type master equation. It is shown
that the resulting equation naturally unifies coherent and dissipative processes:
the commutator term governs the unitary evolution, including corrections to the
Hamiltonian, while the dissipative part describes incoherent processes associated
with neutrino decay and its inverse process in the medium.

A new highly granular time-of-flight neutron detector (HGND) is being developed and constructed for the BM@N (Baryonic Matter at the Nuclotron) experiment to identify neutrons and measure their energies in heavy-ion collisions at beam energies of up to 4 AGeV. The HGND consists of two arms, each with 8 active layers, each of 11×11 plastic scintillator cells 4×4×2.5 cm³ with direct light readout by silicon photomultipliers EQR15 11-6060D-S and copper absorber plates with thickness 3 cm in between. The detector readout electronics is based on a custom-developed board featuring a 100 ps FPGA-based time-to-digital converter (TDC). The complete HGND readout system will comprise eight such boards, each equipped with three Kintex-7 FPGAs and capable of reading out 248 channels.
A fully functional 34-channel detector prototype, corresponding to one quarter of a single active layer, was tested using cosmic muons and the LPI electron beam. In addition, a two-channel prototype was integrated into the BM@N data-acquisition system, including full-chain readout functionality, and tested during the run in April of this year.
Details of the HGND development, readout topology and test results will be presented.

In nucleus-nucleus collisions at energies up to 2 GeV, neutrons constitute a significant fraction of
secondary particles. For their registration and identification, it is proposed to use modules of a High
Granularity Neutron Detector (HGND). The detector has a layered structure, where each active
layer consists of individual cells. This work considers the possibility of replacing passive layers
with active layers made of a high-density scintillator — bismuth orthogermanate Bi₄Ge₃O₁₂ (BGO).
However, the use of BGO for time-of-flight (TOF) measurements is complicated by the long signal
rise time (>100 ns) and requires the development of specialized electronics (amplifier). The report
presents a time-of-flight data analysis method applied to data obtained during testing of a BGO
crystal with the developed amplifier on an experimental test bench. Additionally, the results of
simulations of a prototype detector based on BGO crystals are presented.

A straw-tube forward tracking detector is being considered for the second stage of the Multi-Purpose Detector (MPD) at the NICA collider. It would extend the MPD acceptance to forward rapidities and broaden the accessible physics program. In central heavy-ion collisions, high hit density and ghost hits create a large combinatorial background, making robust track reconstruction challenging. We present recent developments of the ACTS-based reconstruction aimed at improving its performance in this environment.

Recent work focused on two stages that were found to limit the reconstruction performance: space-point creation and track seeding. The space-point algorithm combines measurements from stereo-crossed straw layers. Its ambiguity resolution was studied using a graph neural network, and the deterministic selection was subsequently optimized to improve the balance between reconstruction efficiency and background suppression. In parallel, a custom seeding algorithm was developed to exploit space points from all five tracking stations, instead of the three fixed stations used in the previous ACTS-based setup. This makes seed reconstruction less sensitive to missing or ambiguous space points in individual stations.

With these improvements, high reconstruction efficiency for trackable primary pions is achieved in central Au-Au events at $\sqrt{s_{\rm{NN}}}=11$ GeV simulated with UrQMD, while maintaining high reconstructed-track purity. Further developments will include matching with the forward TOF detector to study its potential for additional ghost suppression.

A wide range of applied research with accelerator ions beam is being implemented at the Flerov Laboratory of Nuclear Reactions JINR. Currently, more than 6,000 hours of accelerated time are allocated to such work per year. The volume of applied research is constantly increasing. To meet the requirements for beams and acceleration time, FLNR is implementing a program to create a new accelerator complex, DC-140.
The accelerator complex is based on the DC-140 cyclotron with an ion source DECRIS-5M. The complex includes three channels with experimental setups. The cyclotron operates at a single frequency of 8.632 MHz and accelerates ions in two modes: the 2nd harmonic to an energy of 4.8 MeV/nucleon and the 3rd harmonic to an energy of 2.214 MeV/nucleon. The DECRIS-5M work on frequency 18 GHz allows obtaining ion beams from 16O to 209Bi. The extraction of the accelerated beam using an electrostatic deflector operating together with a passive magnetic channel and permanent magnets quadrupole (PMQ) ensures high acceleration efficiency. The experimental channels are equipped with all necessary diagnostic systems, a system for forming the sample irradiation field and experimental chambers.
The project started in 2020. The construction of facility has been implemented since 2022. Commissioning of the complex's systems will begin at the end of 2025. The commissioning with accelerated beams started in August 2026. The current status of the project and first experimental results are presented in the report.

Precise determination of the event collision time t_{0} is essential for particle identification with time-of-flight detectors. In the ALICE experiment, the event time can be reconstructed from measured TOF signals by comparing them with expected flight times under different particle-mass hypotheses [1,2]. The corresponding optimization problem is combinatorial, and practical reconstruction procedures therefore employ restricted hypothesis searches and rejection criteria.

We present an exact polynomial-time method for global minimization of the event-time objective function. The algorithm determines the optimal particle hypotheses together with the corresponding t0 without exhaustive enumeration of all hypothesis assignments. The method was validated against brute-force enumeration at low multiplicity, where identical particle assignments, event times, and objective-function values were obtained. It was further benchmarked against the event-time reconstruction procedure implemented in the ALICE O2 framework [3,4] using simulated pp and Pb-Pb events. For typical events, the optimized O2 procedure remains highly competitive in execution time, while the exact method provides a guaranteed global optimum and can therefore serve as a reference for validating heuristic reconstruction approaches.

We also demonstrate ambiguous event configurations for which the restricted search converges to a suboptimal solution, producing a shifted reconstructed event time and incorrect particle assignments, whereas the exact algorithm recovers the global minimum. The proposed method can therefore be used both as a validation tool and as a component of future hybrid event-time reconstruction algorithms.

References

[1] ALICE Collaboration, “Determination of the event collision time with the ALICE detector at the LHC,” European Physical Journal Plus 132, 99 (2017). doi:10.1140/epjp/i2017-11279-1

[2] A. Alici for the ALICE Collaboration, “Particle identification with the ALICE Time-Of-Flight detector at the LHC,” Nuclear Instruments and Methods in Physics Research A 766, 288–291 (2014). doi:10.1016/j.nima.2014.05.059

[3] G. Eulisse and D. Rohr for the ALICE Collaboration, “The O2 software framework and GPU usage in ALICE online and offline reconstruction in Run 3,” EPJ Web of Conferences 295, 05022 (2024). doi:10.1051/epjconf/202429505022

[4] ALICE O2, TOF EventTimeMaker implementation and documentation. EventTimeMaker.h

To increase particle identification quality in the Spherical Neutral Detector (SND) at the VEPP-2000 electron-positron collider, we propose upgrading the ASHIPH (Aerogel, SHifter, PHotomultiplier) Cherenkov counters. With the replacement of the current microchannel-plate photomultipliers (MCP-PMTs) with silicon photomultipliers (SiPMs), we expect the number of detected photons per particle to increase by a factor of 2.5.
The front-end electronics (FEE) for an array of five SiPMs were developed. The SiPM array calibration procedure and its results are presented, and the array homogeneity is estimated. The results of testing the FEE together with a thermal stabilization system inside the SND detector are reported. An ASHIPH-SiPM counter prototype was developed and investigated with a test electron beam to study the light-collection inhomogeneity across the counter. Results for both aerogels (refractive indices n = 1.05 and n = 1.13) are presented. The estimated π/K separation quality is about 6σ.

Noble element detectors (two-phase emission detectors, liquid phase-only detectors, etc.) have many applications in modern research.
For example, they are broadly used in dark matter registration, non-standard neutrino interactions searches and even Standard Model processes observation (CEvNS). Modeling signal generation from these complicated interactions requires precise simulations. The main problem of modeling such phenomena is that various theoretical predictions are inconsistent with each other and compared to experimental data.

In this talk, the current status of NEST: Noble Element Simulation Technique, which is a simulation package dedicated to response of noble elements (xenon and argon) will be discussed and applicability to high energy ranges will be demonstrated.
Also updated models on argon will be discussed, including S1 pulse shaping models.

We consider particle creation of a non‑conformal scalar field in the Early Universe. The deviation from conformality is assumed to be small, which allows us to treat the terms describing the non-conformal scalar field as a perturbation. We derive the Schrödinger equation for the system of gravitational and scalar fields from the path integral making use of a holomorphic representation for the scalar field. In the conformal case, the equation is solved exactly. In the case of a non-conformal field, we use the perturbation theory, and some new features are revealed. When deriving the Schrödinger equation, we obtain an operator that maps the states of the Fock space with a certain number of particles and antiparticles at time t to states corresponding to a subsequent moment of time. The operator appears entirely due to changing of a basis in the Fock space with time. We compare our results with those obtained using the method of diagonalizing the Hamiltonian in the canonical formalism and find that the results are fully consistent. In perspective, we consider the path integral approach as an additional tool for studying particle creation in a gravitational field and cosmological perturbations.

We study scalar particle production in a closed isotropic universe within the extended phase space approach. Unlike the treatments in which the gravitational field is treated classically, we quantize the coupled gravitational and matter degrees of freedom and derive the Schrodinger equation for the wave function of the Universe, including perturbative contributions associated with a slight deviation from conformal coupling. We start from the effective action for scalar and spinor fields interacting with gravity, with the spinor field introduced to cancel vacuum divergences arising in the theory. The gravitational degree of freedom is described in the coordinate representation, while the matter modes are treated in the holomorphic representation. We then analyze particle-production processes as perturbative transitions between quantum states. Unlike the usual path-integral treatment, where perturbations are assumed to be independent of velocities, the perturbative interaction in our model depends on the time derivative of the scale factor. We compare this description with the conventional canonical approach based on Bogoliubov transformations and discuss the relation between the two formulations.

We consider a dilatonic dyon black hole solution
with a gravitational radius of $2 \mu$ and two charges,
$Q_1$ (electric) and $Q_2$ (magnetic), within the framework
of a four-dimensional gravitational model comprising one scalar field and one 2-form. The dilaton coupling constant $\lambda$ is fixed by $\lambda^2 = \frac{3}{2}$. This solution is related to the $A_2$ Toda chain.
The circular orbits of null geodesics are explored, and the fifth-order polynomial master equation governing the photon sphere radius $R_0$
is analyzed. It is shown to admit a unique solution satisfying $R_0 > 2 \mu$.
The circular null geodesics are proven to be unstable.
Finally, the black hole shadow is examined, yielding relations
for the shadow angle and the critical impact parameter.

We explore the quasinormal modes of a massless test scalar field in the gravitational background of a non-extremal dilatonic dyonic black hole. The dyon-like black hole solution is considered within a four-dimensional gravitational model that includes two scalar fields and two 2-forms.
It is governed by two dilatonic coupling vectors (\vec{\lambda}_s) (with (s=1,2)) that satisfy (\vec{\lambda}_1 = \vec{\lambda}_2 = \vec{\lambda}) and (\vec{\lambda}^2 = 1/2). We derive and examine the quasinormal modes of a massless scalar test field in the eikonal limit.
These modes are governed by the solution parameters $\mu > 0$, $P_1 > 0$, and $P_2 > 0$. In the two limiting scenarios -- namely $P_1 = P_2 = 0$ and $P_1 = P_2 = P > 0$ -- our results reduce exactly to the known (eikonal) quasinormal spectra for the Schwarzschild and Reissner-Nordström black holes, respectively.
Numerical higher-order WKB analysis of quasinormal frequencies for two lower levels (for various values of parameters) is also presented.

We present a new gravitational framework in which the conventional conservation of the energy-momentum tensor is relaxed and replaced by a non-conservation law motivated by relativistic thermodynamics. In this approach, the exchange of energy and momentum between matter and the gravitational sector is treated as a fundamental physical effect rather than as an effective description of an unknown dark-energy component. The resulting field equations extend Einstein gravity while retaining the standard geometric description of spacetime and the usual conservation law as a limiting case.

We investigate the cosmological consequences of this non-conserved gravitational dynamics in a homogeneous and isotropic universe. The modified continuity equation introduces an additional matter–spacetime exchange term, which changes the evolution of the cosmic energy density and generates an effective contribution to the expansion dynamics. Remarkably, the resulting cosmological evolution can produce a transition from decelerated to accelerated expansion without introducing a fundamental cosmological constant or an exotic dark-energy fluid. For suitable parameters, the background evolution approaches the behavior of the standard $\Lambda$CDM model while providing a different physical interpretation of the source of late-time acceleration.

The framework therefore offers a thermodynamically motivated alternative to the conventional dark-energy picture and provides a direct connection between gravitational dynamics, energy exchange, and cosmological evolution. We discuss the corresponding expansion history and the prospects for confronting the model with observational cosmology, including distance-redshift measurements and the evolution of the Hubble parameter. The results suggest that violations of energy-momentum conservation, when consistently incorporated into gravitational thermodynamics, may provide a viable route toward understanding cosmic acceleration without requiring an independent dark-energy sector.

One of the predictions of general relativity is the existence of spacetimes with nontrivial topology and causal structure. In principle, the real three-dimensional space could be multiply connected and could contain wormholes. As shown in the work of Novikov, a stable wormhole—if such an object exists—could, in principle, be turned into a time machine. When quantum field fluctuations are taken into account in a spacetime containing such a wormhole, these fluctuations grow significantly as the Cauchy horizon is approached. In particular, the renormalized stress energy tensor of the quantum field diverges at the Cauchy horizon, leading to an infinite energy density. This divergence is commonly interpreted as a sign that building a time machine is impossible—this is the essence of the chronology protection conjecture. However, that conclusion was reached by treating the wormhole throats' motion classically and by evaluating quantum effects in a fixed background geometry.
In contrast, in the present paper we apply quantum mechanics to describe the motion of the wormhole throats. Within this approach, we obtain an estimate for the probability of creating a time machine, and this probability is found to be of order unity. The process closely resembles quantum tunnelling as known from ordinary quantum mechanics.

Spatial anisotropy of the gravitational constant $G$ is a key prediction of the Spin-Density Model (SDM), in which space-time is considered as a dynamic carrier medium. According to the SDM, large-scale polarization of this medium by active galactic nuclei leads to a dependence of the effective gravitational constant on direction, manifesting as a difference in gravitational attraction in the Galactic plane and perpendicular to it. The astrophysical estimate of this effect gives $\Delta G/G \sim 10^{-8}$, whereas in laboratory conditions on Earth the effect should be suppressed by the local gravitational field to $\Delta G/G \sim 10^{-10}$. Existing gravimetric constraints ($\Delta G/G < 6 \times 10^{-10}$) do not contradict this prediction but cannot confirm it due to scale limitations.

This paper argues for the necessity of transitioning to astronomical tests that allow probing the anisotropy of $G$ on scales where the influence of local masses is minimal. Two complementary directions are considered: Lunar Laser Ranging (LLR) and analysis of Trans-Neptunian Object (TNO) anomalies. LLR provides precision measurement of the Moon's orbit and constrains anisotropy parameters ($\alpha_2 \approx 2 \times 10^{-5}$), yet its sensitivity to the anisotropy itself is still inferior to gravimetric constraints. TNOs, in turn, provide a statistically significant sample of orbits at distances of 30–150 AU, where the contribution of carrier medium polarization becomes relatively more prominent. Anomalies in the distribution of TNO orbital parameters, usually attributed to a hypothetical "Planet Nine," receive a natural explanation within the SDM as a consequence of the large-scale polarization "texture" of space-time.

Prospects for using long-period comets and the Oort cloud, as well as future surveys (LSST), to refine SDM predictions are discussed. It is shown that a joint analysis of LLR and TNO data allows not only testing the hypothesis of spatial anisotropy of gravity but also verifying the ontological principles of the SDM as a whole. Specific experimental and observational strategies aimed at detecting the effect at the $10^{-10}$ level and below are proposed.

Keywords: spatial anisotropy of gravity; gravitational constant; Spin-Density Model; Lunar Laser Ranging; Trans-Neptunian Objects; dark matter; Planet Nine.

High-energy astrophysical neutrinos can provide a probe of hadronic processes at their production site constraining models of the most energetic cosmic ray sources. The diffuse astrophysical neutrino flux was discovered by the IceCube experiment more than a decade ago but still remains largely unexplored. After the deployment campaign in 2026, the Baikal-GVD neutrino telescope has reached the detection volume of 0.8 km3 and it is planned to further expand it to 1km3 in the next two-three years. Meanwhile the detector joins the study of the origins of high-energy cosmic neutrinos with the data accumulated at the construction phase. In present report we discuss the status and recent physics results of Baikal-GVD among them are the measurement of the diffuse astrophysical neutrino flux and neutrino source searches.

The High-energy Underwater Neutrino Telescope (HUNT) project aims to identify astrophysical neutrino sources, particularly those associated with ultra-high-energy gamma-ray emission observed by LHAASO. We present the status of its prototype program in Lake Baikal, covering deployment campaigns and preliminary results from 2024 to 2026. Deployments progressed from 12 optical modules with 20-inch photomultiplier tubes in 2024 to 24 complete optical modules in 2025, followed by a second full prototype string in 2026. These campaigns enabled studies of optical-module response, depth-dependent counting rates, and underwater hardware reliability. We report preliminary analyses of muon-like events and joint event studies with Baikal-GVD. Progress in LED timing calibration and optical-module positioning is also presented. These results provide technical input and operational experience for further development of Baikal-HUNT and support future joint observations with Baikal-GVD.

We investigate and make theoretical estimates for the neutrino flux above 150 TeV in a scenario with a nearby source in the Cygnus region, the existence of which is motivated by the LHAASO gamma-ray bubble observations. By combining a state-of-the-art model of galactic cosmic rays with the contribution from a local source within the framework of a two-zone diffusion model, we investigate the neutrino signal for anisotropy.

The formation of a neutrino cluster due to an attractive interaction with a hypothetical light scalar boson is studied. The density distribution of the neutrino gas within the cluster is obtained for various system parameters. It is shown that, in addition to forming a cluster in space, the neutrino gas within it can form a superfluid condensate. An energy gap equation is derived for such a system, and the phase transition temperature and coherence length within the cluster are found. Constraints on the parameters of the interaction leading to neutrino superfluidity are derived. It is found that the superfluid condensate within the cluster consists of relic neutrinos. A neutrino cluster cooling channel based on the Cherenkov emission of neutrinos in matter is studied if the cluster forms in the early universe. A temperature range is obtained for which Cherenkov cooling of the cluster is effective. The possible contribution of neutrino clusters to dark matter is briefly discussed.

Strange quark matter (SQM) is a compelling candidate for the true ground state of quantum chromodynamics (QCD) at high baryon density. Within the Bodmer-Witten-Terazawa hypothesis, if SQM has a lower energy per baryon than ordinary hadronic matter, neutron stars can convert to strange quark stars (SQSs). Stable clusters of SQM, strangelets, can be produced in dense QCD phase transitions, releasing up to $\sim10^{53}$ erg. Strangelets consist of approximately equal numbers of up, down, and strange quarks; their baryon number $A$ is one third of the total quark number, and their net electric charge is $Z$. Both MIT-bag and Nambu-Jona-Lasinio descriptions predict mass-to-charge ratios $m_S/|Z|\sim30$ to $60$ GeV/$c^2$ for $A\sim10^{2}$ to $10^{5}$. A key formation channel is the transition from the two-flavor color-superconducting (2SC) phase to the color-flavor-locked (CFL) phase in dense quark matter. Diquark condensation, fragmentation of Fermi surfaces, and surface emission of quark clusters can produce strangelets, while strangelet-anti-strangelet annihilation, $S\bar{S}\to\gamma\gamma$, can generate narrow, monochromatic very-high-energy (VHE) $\gamma$-ray lines.

This work develops a unified framework connecting QCD-motivated strangelet production to observable multi-messenger fluxes. A phenomenological production-rate model is introduced that balances geometric growth, $\dot N(A)\propto (A/A_{\rm peak})^{2/3}$, against exponential suppression from multi-fragmentation and coalescence. The framework is applied to three representative astrophysical environments: (i) HESS J1731$-$347, a steady SQS candidate with $M=0.77^{+0.20}_{-0.17}M_\odot$ and $R=10.4^{+0.86}_{-0.78}$ km, whose 2SC-CFL interface can inject strangelets into the surrounding supernova remnant; (ii) GW170817, the first binary neutron-star merger, where the hadron-to-quark transition in the post-merger remnant can produce a burst-like strangelet flux; and (iii) GRB 250702B, an ultra-long gamma-ray burst with duration $>25{,}000$ s and $E_{\rm iso}>1.4\times10^{54}$ erg, providing an extreme burst-driven channel. Constraints from H.E.S.S., Fermi-LAT, MAGIC-II, and the projected Cherenkov Telescope Array (CTA) are compiled. The baseline scenario lies near the CTA sensitivity threshold ($\sim10^{-13}$ ph cm$^{-2}$ s$^{-1}$ at 1 TeV); the optimistic scenario is already excluded by H.E.S.S., while the conservative scenario requires next-generation instruments.

A complementary direct-detection program targets macroscopic SQM composites such as nuclearites and Q-balls. Although microscopic strangelets are unlikely to survive interstellar propagation, these heavier objects possess extremely large mass-to-charge ratios and high ionization densities, allowing them to traverse the interstellar medium and penetrate the terrestrial atmosphere. Their passage would produce bright, continuous high-ionization tracks, thermal shock fronts, and slow luminous transits in large-volume detectors. Existing limits from MACRO, SLIM, ANTARES, and IceCube already constrain parts of the parameter space, while future facilities including LHAASO, KM3NeT/ARCA, SQM-ISS, and gravitational-wave observatories will provide complementary sensitivity. Combining narrow VHE $\gamma$-ray line searches with direct macro-SQM detection and multi-messenger follow-up of neutron stars, mergers, and GRBs offer a decisive test of the strange quark matter hypothesis.

Red-giant evolution is sensitive to non-standard channels of energy loss and therefore provides a probe of new physics.
Such losses increase the luminosity of the tip of the red-giant branch
(TRGB), enabling constraints on the axion--electron coupling $g_{ae}$.
In this talk, we present cluster-specific stellar-evolution calculations
with MESA for 27 Galactic globular clusters, including the implementation
of axion emission and its impact on the predicted TRGB luminosity.
Particular attention is given to the assessment of theoretical uncertainties associated with thermal-neutrino emission, electron conduction, radiative opacity, nuclear reaction rates, convection, and other modelling assumptions. We examine how these theoretical uncertainties affect the predicted TRGB luminosities and the resulting constraints on the axion–electron coupling.

We briefly outline the joint profile-likelihood analysis used to
compare these predictions with TRGB measurements for 24 clusters,
after excluding three hot-flasher systems. Retaining shared
uncertainties as correlated nuisance parameters, we obtain
a 95% confidence-level power-constrained upper limit
of $g_{ae} < 6.4 \times 10^{-14}$.

Star formation processes are very important in the Universe. In particular, the formation of massive stars results in supernova explosions with subsequent acceleration of cosmic rays (CR) in supernova remnants (SNRs). We show that the currently-available elemental spectra of protons, Helium, CNO group nuclei, and Iron in the energy range from 40 GeV to 100--500 PeV are well described with two separate populations of Galactic SNRs. We propose a scenario where the extragalactic CR component is produced by a third distinct population of SNRs; these SNRs probably have sub-relativistic speeds of shock waves and/or are the remnants of powerful hypernovae. Then we discuss a possibility that these three SNR populations dominate the entire observable spectrum of CR protons and nuclei spanning from 1 GeV to 100 EeV. Some details are available in astro-ph/2606.02748 (submitted to MNRAS).

Astrophysical sources of ultra-high-energy cosmic rays (UHECRs) remain unidentified, and no nearby cosmic accelerators are established even for the highest-energy events. In addition, puzzling correlations of a fraction of UHECR flux with distant blazars were found by HiRes and, recently, Telescope Array experiments. Here we propose that dark matter can provide a mechanism to effectively transfer UHECRs from distant sources: dark-matter particles are boosted by UHECRs near the source and pass their momentum to baryons close to the observer. The probability of this relay is not negligible because of the growth of dark-matter–baryon cross section with energy. We demonstrate that the effect is observable for the fermionic dark matter of the mass $m_\mathrm{DM} \sim 25 \, \mathrm{MeV}$ and discuss possible observational signatures of this mechanism.

The Baksan large neutrino telescope is a large-scale liquid scintillation detector under development at the Baksan neutrino observatory of the Institute for Nuclear Research of the Russian Academy of Sciences. The detector will employ a large number of photomultiplier tubes (PMTs). The Earth's magnetic field can significantly affect PMT perfomance and, consequently, the energy and timing characteristics of the detector. Therefore, a magnetic field compensation system is required to ensure stable operation of the photodetectors.
The influence of the Earth's magnetic field on the Hamamatsu R7081-100 WA-S70 PMT, selected for the 5-ton BLNT prototype, was experimentally investigated. The measurements were performed under controlled magnetic fields generated by Helmholtz coils.The PMT gain, peak-to-valley ratio of the single-photoelectron charge spectrum, and transit-time characteristics were studied as functions of the magnetic field components. The results demonstrate that magnetic fields of the order of 0.1 G can already affect the PMT response. Thus, developing a magnetic field compensation system is a necessary task.
The developed system provides an active approach for producing a homogeneous compensating magnetic field over a large detector volume.

The conceptual design of the SPASCHARM facility [1] calls for its relocation to channel No. 24 of the U-70 Accelerator Complex, with a muon detector positioned at the end of the facility. This detector is required to identify J/ψ particles via their decay into two muons (μ+μ−) and subsequently to search for χc2 (spin 2) and χc1 (spin 1) through their decays into J/ψ + γ, with the ultimate goal of measuring the gluon contribution to the proton spin. This paper presents the concept for the muon detector's construction. The proposed design comprises three pairs of tracking planes with a total area of ~12 m², interleaved with steel filters assembled from disks approximately 4 m in diameter and 220 mm thick. Each pair of tracking planes consists of two identical planes oriented orthogonally to one another, and each such plane is in turn composed of two layers of drift tubes housed in aluminum tubes 3.7 m long with an inner diameter of 50 mm.
Openings of ~20 × 20 cm² are provided in the central regions of the steel disks and tracking planes, coaxial with the primary proton beam, to prevent the tracking planes from being overloaded by primary protons and the products of their interaction with the steel disk material.

Radiation hardness studies of the CMS detector's cathode strip chambers have been conducted at the GIF++ gamma irradiation facility at CERN since 2016. During the studies, ME1/1 and ME2/1 chambers, which differ in design and operate in CMS under high background rate, were subjected to intense irradiation. The accumulated charge per unit length of the anode wire reached 1030 mC/cm for ME2/1 and 1170 mC/cm for ME1/1, which is more than three times higher than the integral dose expected for the entire period of HL-LHC operation. The characteristics of the chambers were studied periodically in tests with SPS muon beams. There are no signs of radiation-induced degradation of the chambers. The data obtained confirm the high radiation hardness of cathode strip chambers for operation in extreme conditions of HL-LHC.

The LHC Run 3 concluded in June 2026. Over nearly four years of operation, the ALICE experiment [1] collected $\sim$150 pb$^{-1}$ of $\text{pp}$ and $\sim$6.9 nb$^{-1}$ of the first $\text{Pb}{-}\text{Pb}$ collisions data, exceeding the cumulative dataset from previous Run 1 and Run 2. This period was also remarkable for the new
light-ion program, featuring the first $\text{Ne}{-}\text{Ne}$ and $\text{O}{-}\text{O}$ collisions at the LHC.

Two of the new ALICE detectors, Inner Tracking System (ITS) and FT0 – a Cherenkov
detector within the Fast Interaction Trigger (FIT) [2] system – have become essential for data taking. Both are widely used for event selection, particularly based on the vertex position in recent Run 3 analysis. Moreover, the FT0 data is a source for multiplicity classification in $\text{pp}$ collisions and centrality classification in various ion collision systems. In addition, the FT0 serves as the primary ALICE luminometer in pp collisions and the machine background intensity estimator for the ALICE experiment. These capabilities of the FT0 detector are enabled by the high performance of the front-end electronics and its integration with the FIT Detector Control System (DCS) [3], which allows for the correction of trigger counts based on the LHC filling scheme.

This talk is devoted to the integration of the LHC interface signals with FT0 DCS. This connection enabled the Run 3 instantaneous luminosity measurement, online background estimator and other automated algorithms, ultimately contributing to the excellent performance of the FT0.

References

1. ALICE upgrades during the LHC Long Shutdown 2 / S. Acharya [et al.] // Journal of instrumentation.
   – 2024. – Vol. 19, no. 05. – P05062. doi: https://doi.org/ 10.1088/1748-0221/19/05/P05062
2. Slupecki M. Fast Interaction Trigger for ALICE upgrade //Nuclear Instruments and Methods in Physics
   Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. – 2022. – Vol.1039. – P.167021. doi: https://doi.org/10.1016/j.nima.2022.167021
3. ALICE fast interaction trigger detector control system for the LHC Run 3 // M. Sukhanov [et al.] //
   International Journal of Modern Physics E. – 2026. – Vol. 35. – P.2641008. doi: https://doi.org/10.1142/S0218301326410089

Homogeneous calorimeters based on scintillation single crystals are widely used in high-energy physics due to their good energy, position and time resolution. A small precise 256-channel photon spectrometer (PHOS256) based on PbWO$_4$ crystals is proposed for an experiment at the U-70 accelerator facility for measurements of spectra of neutral mesons and direct photons with proton, pion, and kaon beams of momenta 26.5–50 GeV/c on nuclear targets.

Such a detector can also be used for measurements of the linear photon polarization using photon conversion into e+e- pair on a dedicated converter in front of the calorimeter via analyzing an asymmetry of clusters containing both particles. The calorimeter’s design is optimized using simulations with the Pythia and Geant4 packages. The calorimeter construction will be discussed - the PbWO$_4$ crystals, the avalanche photodetectors attached to the crystals, the main electronics, and the cooling equipment. The reconstruction of photon pairs from π$^0$ mesons and η mesons will be considered to determine the optimal calorimeter position.

First results on the detector response to the cosmic muons and the comparison with results of Monte-Carlo simulations will be presented.

The front-end electronics of the modern experiments is often designed with the use of sampling ADC. The signal wave-form measured by such electronics carries information about the basic parameters of the signal of interest, its amplitude and time. Timing measurement of the sampled wave-form is a challenging task, especially when one aims for nanosecond and sub-nanosecond resolution having the sampling rate of tens MHz.

Using data from the ALICE electromagnetic calorimeter PHOS, we develop and compare algorithms for the signal timing measurement. The comparison was performed on small samples. Both classical data comparison algorithms and bootstrap techniques are used. The developed methods of timing measurement are considered as an important input towards precision measurements of signal time in high-energy experiments.

This paper presents a statistical comparison of two methods for determining the velocity of a heavy ion using a semiconductor detector (PIN diode): the method based on a subjective optimization criterion that employs the mathematical formalism of subjective modeling (MFSM) proposed by Yu. P. Pytyev, and the generalized cross-validation (GCV) method. The MFSM makes it possible to formulate mathematically both a subjective model of the object under study and a subjective mathematical model of its measurements and their subjective interpretation. Using the MFSM, one can mathematically formalize the subjective judgments of the researcher-modeler regarding the physical properties of the object under study, the means of its measurement, the mathematical properties of noise, and so on; all such subjective information is based on the researcher-modeler's scientific experience and scientific intuition. The GCV (Generalized Cross-Validation) method is a statistical method used to select the regularization parameter when solving ill-posed problems, smoothing data, or reconstructing signals. GCV helps to efficiently estimate noise and to choose smoothing in problems where direct estimation of parameters is difficult. A computational experiment has been carried out that simulates the acquisition of a signal at the detector with a halved ion registration rate, which makes it possible to assess how sensitive the two compared methods are to the sampling rate of the recording equipment.

Unusual rectangular structures were observed for the first time using a resulting fragment mass–mass matrix in experiments on the FOBOS spectrometer studying the spontaneous fission of 248Cm and 252Cf nuclei. These structures are associated with a large "missing" mass and are bounded by magic nuclei, and they were interpreted as a manifestation of a new exotic decay mode – triple collinear cluster decay (TCCD). These pioneering results have been repeatedly confirmed and refined in a series of subsequent experiments. At the stage of interpreting the obtained data, an assessment of the statistical reliability of the aforementioned linear structures in the mass–mass distribution of the registered fragments is required.

This report presents the results of a comparison between assessments of the statistical reliability of point linear structures using the standard Hough transform and a modified Hough transform that offers greater robustness to noise and outliers. In the classical Hough method, each experimental point is treated as a point source of votes in parameter space. To reduce the influence of extreme points, random points are generated inside a bounding circle, which lowers the probability of false maxima along diagonal directions. However, this approach does not account for finite measurement accuracy. In this work, a Hough method has been implemented in a way that each experimental point is represented by a circle whose radius corresponds to the measurement uncertainty. The sought line is then treated as a band of finite thickness (greater than one pixel). Such a band may fully or partially overlap the "smeared" point. The simulation was carried out on a 100×100 pixel field with approximately 25 random points generated. During voting, partial intersections of the line band with the uncertainty regions of the points were taken into account. The results of both methods were compared. It is shown that the probability of a random occurrence of linear structures on the plane does not exceed 2% for either method.

We present the Dark Energy Survey Year 6 3x2pt analysis, which combines cosmic shear, galaxy clustering, and galaxy-galaxy lensing measurements across ~4000 deg². Using an unprecedented sample of lens and source galaxies, this study delivers some of the most precise constraints to date on key cosmological parameters, including the matter density Ωₘ and the amplitude of cosmic structure σ₈. Our findings reveal a mild but intriguing tension with Planck CMB predictions under the standard ΛCDM mode. This analysis demonstrates the power of joint probes in testing dark energy and sets a benchmark for upcoming surveys like LSST and Euclid.

General Relativity (GR), developed over 110 years ago, has successfully passed numerous astronomical tests. However, most of these tests have tested GR in the weak gravitational field approximation. Astronomers believe that stellar-mass black holes exist in binary systems, as well as supermassive black holes at the centers of galaxies. These astronomical objects give an opportunity to test GR predictions not only in the weak gravitational field limit, but also in the strong gravitational field limit, in particular, black hole parameters could be evaluated. Astronomical observations of astrophysical black holes also provide constraints on the parameters of alternative theories of gravity. In particular, we discuss shadow observations in $Sgr A^*$ and $M87^*$ to test GR predictions. By analyzing GRAVITY+ and Keck observations of bright stars (including S301) moving in the vicinity of the galactic center, we also discuss tests of general relativity and alternative theories of gravity.

In the Bergmann-Wagoner-Nordtvedt class of scalar-tensor theories, well known are wormhole solutions existing in the phantom sector of the theory. Exceptional wormholes exist in the canonical sector owing to the phenomenon of conformal continuation, the situation where the Einstein frame manifold maps to only a region of the Jordan frame manifold, and the latter is smoothly continued to a region with negative effective gravitational coupling. We discuss the existence conditions and the stability properties of exceptional wormholes, in particular, those with and without an electromagnetic field in the Brans-Dicke theory: it is shown how the electromagnetic field plays a stabilizing role.

We present simulated detectability of traversable wormholes (WHs) in wide binary astrophysical systems without accretion (dormant binary systems) and in the Galactic center. The wormhole spacetime is represented as a gluing of two asymptotically flat Schwarzschild spacetimes, without specifying the detailed geometry of the throat. We consider a traversable WH candidate as a compact object in a binary system, whose companion star is perturbed by a massive object on an elliptical orbit on the other side of the WHthroat. In the case of a supermassive BH as WH candidate the perturbing acceleration is analyzed and compared with the stochastic gravitational influence of surrounding stars. For dormant wide binary systems, we analyze the radial velocity perturbations and their distinguishability from triple-system scenario. Under the model assumptions and the considered observational sampling, radial velocity perturbations are detectable in simulations with an observational accuracy of 1.5 km/s for all considered observation time spans. For a more conservative accuracy of 10 km/s, the spectral analysis methods become statistically significant after ≈ 17 years of simulated data accumulation. The spectral and non-parametric methods significantly reduce the required accumulation time compared to matched-filtering applied in isolation.

We study the neutrino sector of an eight-dimensional two-brane model based on $f(R)$ gravity. The metric is warped:

$ds^{2} = e^{2\gamma(u)}\eta_{\mu\nu}dx^{\mu}dx^{\nu} - du^{2} - r^{2}(u)\,d\Omega^{2}_{n-1}.$

Here $u$ is the radial extra coordinate, and the remaining three coordinates parametrise a compact internal manifold. The classical field equations admit a countable family of solutions in which $\gamma(u)$ and $r(u)$ vanish at two endpoints $u_{1}$ and $u_{2}$. Matter fields accumulate near these endpoints. A pair of four-dimensional branes therefore forms spontaneously, as a solution of the gravitational dynamics. Nothing is assumed about their existence, position or tension.

We then derive the consequences of this geometry for the matter sector. Massless bulk fermions obey

$\left(\partial_{u} + \frac{\partial_ur^{}(u)}{2r(u)} + 2\partial_u\gamma(u)\right) Y(u) = 0$

along $u$. The solution is sharply peaked at $u_{1}$ and $u_{2}$. On the compact factor, a normalisable chiral zero mode requires a suitable background gauge field. Each bulk fermion then has one chiral zero mode per brane, and the two sets of modes are effectively decoupled, because $|Y(u)|^{2}$ is exponentially small between the branes. The Higgs vacuum expectation value differs on the two branes, so masses and couplings on brane-2 are free up to $m_{D}$. The gauge zero mode behaves differently: it is constant along $u$, so the $Z$ boson is common to both branes.

Dimensional reduction of the neutral-current action reflects this structure. Besides the canonical on-brane vertices, it produces off-diagonal neutrino–$Z$ couplings weighted by the overlap of the two profile functions. Exponential localisation makes this overlap of order $\exp\left[-m(u_{2}-u_{1})\right]$, that is about $10^{-35}$ for an interbrane distance $u_{2}-u_{1} \approx 80\,m_{D}^{-1}$ and $m \sim 1$. The geometry thus supplies an exponentially small parameter without fine-tuning. A seesaw with the brane-2 vacuum expectation value places a superheavy sterile neutrino on the hidden brane, and the off-diagonal vertex lets it decay at a rate suppressed by the squared overlap. The resulting lifetime is cosmological, so the particle is a dark-matter candidate.

The decay $\nu^{(2)} \to \nu^{(1)} Z^{\ast} \to \nu^{(1)}\nu^{(1)}\bar{\nu}^{(1)}$ gives a quasi-monochromatic flux peaked at $E_{\nu} \sim m_{2}$. We estimate the diffuse rate and compare it with IceCube and KM3NeT data, including KM3-230213A at $2.2 \times 10^{8}\,\mathrm{GeV}$. The competing annihilation channel $\bar{\nu}^{(2)}\nu^{(2)} \to Z^{\ast} \to \bar{\nu}^{(1)}\nu^{(1)}$ falls about 18 orders of magnitude short, because its production rate scales as $m_{2}^{-4}$.

The standard cosmological model $\Lambda\mathrm{CDM}$, successfully describes large-scale structure of the Universe. However, several problems on galactic scales motivate studies of alternative dark matter (DM) models. One of such models is self-interacting dark matter (SIDM), where interactions between DM particles can change the internal structure of DM halos.