Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV

TL;DR

This paper investigates how the density of charged particles produced at mid-rapidity varies with collision centrality in lead-lead collisions at 2.76 TeV, revealing a factor of two increase from peripheral to central collisions and comparing results with theoretical models.

Contribution

It provides the first detailed measurement of centrality dependence of charged-particle multiplicity at this energy and compares it with models to understand particle production mechanisms.

Findings

Charged-particle density per participant pair increases by a factor of 2 from peripheral to central collisions.

The centrality dependence pattern is similar to that at lower energies.

Data are consistent with certain particle production models.

Abstract

The centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor 2 from peripheral (70-80%) to central (0-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.