Speaker
Description
The study of the associated production of $J/\psi$-mesons and
photons is very impotent to verify perturbative quantum
chromodynamics, factorization approaches, heavy quark to heavy
quarkonium hadronization models and to extracting the Parton
Distribution Function (PDF) of gluon in a proton from experimental
data. In this paper, we study the associated production of
$J/\psi$-mesons and photons at the energies of the Large Hadron
Collider using the Parton Reggeization Approach (PRA) [1], which is
based on Lipatov's effective field theory [2] and the modified
Kimber-Martin-Ryskin model for unintegrated PDFs [3, 4]. We use two
different heavy-quark to heavy quarkonium hadronization models: the
non-relativistic quantum chromodynamics (NRQCD) [5] and the improved
color evaporation model (ICEM) [6].
We have found that the PRA based predictions for production cross
sections are higher than next-to-leading order collinear parton
model results. We have shown that contributions of the direct
production processes via the color-octet intermediate states in the
NRQCD are suppressed relatively to the process via the color-singlet
intermediate state, so the Color Singlet Model (CSM) can be used for
predictions at the $p_{TJ/\psi}<40~\text{GeV}$. The long distance
matrix elements of the NRQCD and ICEM parameter $F_\psi$ in the
calculations are taken as they have been obtained to describe
experimental data of the $J/\psi$-meson prompt production at the LHC
energies.
We have predicted various differential cross-sections for associated
production of $J/\psi$-mesons and photons in the PRA at the
center-of-mass energy $\sqrt{s} = 13$ TeV in the central rapidity
region. We have obtained that the PRA using the CSM cross-sections
strongly overestimate the results obtained in the PRA using the ICEM
and this difference increases as more as the cutoff on the photon
transverse momentum $p_T$ becomes larger. The results of this study
indicate that there are big difference between the ICEM based and
the NRQCD based predictions for the associated $J/\psi+\gamma$
production that can be used for discrimination heavy quark to heavy
quarkonium hadronization models.
[1] M.A. Nefedov, V.A. Saleev, and A.V. Shipilova. Dijet azimuthal decorrelations at the LHC in the parton Reggeization approach. Physical Review D, 87(9):094030, 2013.
[2] L.N. Lipatov. Gauge invariant effective action for high energy processes in QCD. Nuclear Physics B, 452(1-2):369–397, 1995.
[3] M.A. Kimber, A.D. Martin, and M.G. Ryskin. Unintegrated parton distributions. Physical Review D, 63(11):114027, 2001.
[4] M.A. Nefedov and V.A. Saleev. High-energy factorization for the Drell-Yan process in $pp$ and $p\bar{p}$ collisions with new unintegrated PDFs. Physical Review D, 102(11):114018, 2020.
[5] G.T. Bodwin, E. Braaten, and G.P. Lepage. Rigorous QCD analysis of inclusive annihilation and production of heavy quarkonium. Physical Review D, 51(3):1125, 1995.
[6] Y.Q. Ma, R. Vogt. Quarkonium production in an improved color evaporation model. Physical Review D, 94(11), 114029, 2016.
