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SUMMARY:Influence of Gaussian and non-Gaussian elementary sources on high-
 order multiplicity cumulants in a toy model of relativistic nucleus-nucleu
 s collisions
DTSTART;VALUE=DATE-TIME:20261028T133500Z
DTEND;VALUE=DATE-TIME:20261028T135000Z
DTSTAMP;VALUE=DATE-TIME:20261028T160716Z
UID:indico-contribution-6299@cern.ch
DESCRIPTION:Speakers: Alexandr Zarshchikov (Saint Petersburg State Univers
 ity)\nA.Zarchikov\, G.A.Feofilov*\n \n         Saint-Petersburg University
 \, St. Petersburg State University\, SPbSU\,\n        SPbU\, 7/9 Universit
 etskaya nab.\, St. Petersburg\, 199034 Russia.\n        *e-mail: g.feofilo
 v@spbsu.ru\nHigh-order cumulants of event-by-event multiplicity distributi
 ons are widely used in the search for the QCD critical point in relativist
 ic 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 vo
 lume fluctuations and by the procedure of centrality class selection[3].\n
 \nIn this work\, we study these effects using a simple toy Monte Carlo mod
 el of nucleus-nucleus collisions. The collision geometry is described thro
 ugh the impact parameter and the corresponding number of participant nucle
 ons. Particle multiplicity is generated as a superposition of elementary n
 ucleon-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 fin
 al-state multiplicity\, due to the admixture of events with different coll
 ision geometry and different effective volume.\n\nThe model is then extend
 ed 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 c
 ritical point\, and  trivial contribution caused by the volume fluctuation
 s. Special attention is paid to the comparison of multiplicity-based event
  -by-event selection of  narrow classes of participating nucleons (Npart).
 \n\nThe results demonstrate that the measured values of high-order cumulan
 ts may be significantly distorted by centrality and volume fluctuations ev
 en 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.\n\n \nThe a
 uthors acknowledge Saint-Petersburg State University for a research projec
 t ID: 153212394\n \nReferences:\n[1]. M. A. Stephanov\, Phys. Rev. Lett. 1
 02\, 032301 (2009).\n\n[2]. Hannah Elfner and Berndt Müller 2023\, J. Phy
 s. G: Nucl. Part. Phys. 50 103001.\n\n[3]. G.Feofilov\, Phys.Part and Nucl
 .\, 2026\, vol.57\, No.3\, pp 401-406.\n\nhttps://indico.particle.mephi.ru
 /event/626/contributions/6299/
LOCATION: Conference Hall 2
URL:https://indico.particle.mephi.ru/event/626/contributions/6299/
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