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SUMMARY:Centrality and Event Registration Efficiency Determination in Xe+C
 sI Collisions at BM@N
DTSTART;VALUE=DATE-TIME:20261027T162500Z
DTEND;VALUE=DATE-TIME:20261027T163000Z
DTSTAMP;VALUE=DATE-TIME:20261025T175759Z
UID:indico-contribution-6499@cern.ch
DESCRIPTION:Speakers: Dim Idrisov ()\nCentrality determination is an essen
 tial step in the analysis of heavy-ion collisions and the comparison of ex
 perimental results with model calculations. At beam energies of a few GeV 
 per nucleon\, trigger selection and the primary-vertex reconstruction requ
 irement preferentially suppress peripheral events. Accounting for these lo
 sses is necessary to define centrality classes relative to the total inela
 stic nucleus–nucleus cross section.\nThis work presents centrality deter
 mination 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-particl
 e multiplicity and two approaches: the Monte Carlo Glauber method and a mo
 dified direct reconstruction method based on Bayes’ theorem. In the latt
 er approach\, the conditional multiplicity distribution at a fixed impact 
 parameter is described by a gamma parametrization using fully reconstructe
 d simulated events. The multiplicity dependence of the event registration 
 and selection efficiency is reconstructed with both methods\, while its im
 pact-parameter dependence is also obtained with the direct reconstruction 
 method.\nThe sensitivity of the results to nuclear geometry parameters\, t
 he inelastic nucleon–nucleon cross section\, and the choice of transport
  model is investigated. The Monte Carlo Glauber method yields an integrate
 d efficiency of 72.72%\, with deviations of −1.55 and +0.86 percentage p
 oints corresponding to the envelope of the variations considered. The mean
  and standard deviation of the direct reconstruction results obtained usin
 g DCM-QGSM-SMM\, UrQMD-AMC\, JAM2 MD2\, and SMASH are (72.8 ± 1.0)%. Thes
 e estimates characterize the model-related uncertainty components investig
 ated. The shape of the multiplicity-dependent efficiency is validated by c
 omparing experimental distributions recorded with the CCT2 and BT triggers
 . The two methods yield consistent results\, with the largest model depend
 ence observed in the peripheral region.\n\nhttps://indico.particle.mephi.r
 u/event/626/contributions/6499/
LOCATION:Sevastopol hotel Conference Hall 1
URL:https://indico.particle.mephi.ru/event/626/contributions/6499/
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