Centrality determination of Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with ALICE

TL;DR

This paper details the methods used by ALICE to determine the centrality of Pb-Pb collisions at 2.76 TeV, linking collision geometry to QCD matter properties and enabling comparisons across experiments and models.

Contribution

It introduces a centrality determination method based on a Glauber model for Pb-Pb collisions at 2.76 TeV, validated with experimental data.

Findings

Centrality correlates with collision geometry parameters.

Glauber model estimates are consistent with experimental data.

Provides a standardized tool for cross-experiment comparisons.

Abstract

This publication describes the methods used to measure the centrality of inelastic Pb-Pb collisions at a center-of-mass energy of 2.76 TeV per colliding nucleon pair with ALICE. The centrality is a key parameter in the study of the properties of QCD matter at extreme temperature and energy density, because it is directly related to the initial overlap region of the colliding nuclei. Geometrical properties of the collision, such as the number of participating nucleons and number of binary nucleon-nucleon collisions, are deduced from a Glauber model with a sharp impact parameter selection, and shown to be consistent with those extracted from the data. The centrality determination provides a tool to compare ALICE measurements with those of other experiments and with theoretical calculations.