firstname = "Tatiana"
lastname = "Drozhzhova"
email = "tatiana.drozhzhova@cern.ch"
affiliation = "St.Petersburg State University"
city = "St.Petersburg"
country = "Russia"
passportname = ""
birthday = ""
citizenship = ""
passportnumber = ""
passportissued = ""
passportexpire = ""
workplace = ""
workaddress = ""
visadates = ""
talktitle = "Evaluation of centrality classes based on Glauber  Monte-Carlo model in heavy-ion collisions at high energy "
section = "A - Particle physics"
talkabstract = "Fluctuations in physical observables in heavy-ion collisions have been a topic of interest for some years as they may provide important signals regarding the formation of quark-gluon plasma (QGP). For studying fluctuations and searching delicate effect it is necessary to determine precisely measurement`s parameters (to fix the centrality classes) when the observable`s fluctuation is minimal.
This work is connected with heavy-ions experiments in CERN at LHC energies and proposes the method of estimating the centrality classes where the fluctuations are minimized based on the analysis of RHIC experiments (WA97 [1], WA98 [2]).  The main goal of this work is minimization of trivial fluctuations of observables by determination of the centrality classes width influence on the fluctuations of observables.
For that purpose the Monte-Carlo generator of Pb-Pb collisions at 2,76TeV was created based on Glauber Model. We consider MC simulations due to the possibility of extraction of the information about impact parameter and number of nucleons participated in collisions. Using connection between multiplicity and number of nucleons participated in the collision we can evaluate the multiplicity which is measured on the experiments. This data makes the distinctions for different classes of centrality evident.
 We compared two methods of determination of centrality classes by impact parameter and multiplicity. Analysing the distribution of number of participated nucleons (Npart) in different centrality classes we can evaluate the value of RMS (root mean square) and mean value of Npart in each centrality class with the different widths. As a result, for all values of multiplicity and the impact parameter including the central and peripheral collisions the value of centrality selection bins was determined in percentage wise of widths in the minimum bias cross section where the fluctuations of the observable values are minimized. Using this method one can make analysis of the reconstructed data for different experiments of NN collisions at high energy (like ALICE [3]) to determine conditions where the observables fluctuations will be minimized.

References
1. N.Carrer for the WA97 col.,// Nuclear Physics A661 (1999) 357c-361c
2. WA98 Collaboration, //Phys.Rev. C, vol 65, 054912
3. ALICE collaboration // Phys. Rev. Letters, 106, 032301 (2011)."
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