Dependence on pseudorapidity and centrality of charged hadron production in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2.76 TeV

TL;DR

This paper reports on measurements of charged hadron production in lead-lead collisions at 2.76 TeV, analyzing how it varies with pseudorapidity and collision centrality, providing insights into particle production mechanisms in heavy-ion collisions.

Contribution

It presents the first detailed measurement of charged hadron multiplicity as a function of pseudorapidity and centrality at this energy using the CMS detector, with two consistent measurement methods.

Findings

Charged hadron multiplicity density at eta=0 is 1612 +/- 55.

Results are consistent with previous measurements and model predictions.

The study enhances understanding of particle production in high-energy heavy-ion collisions.

Abstract

A measurement is presented of the charged hadron multiplicity in hadronic PbPb collisions, as a function of pseudorapidity and centrality, at a collision energy of 2.76 TeV per nucleon pair. The data sample is collected using the CMS detector and a minimum-bias trigger, with the CMS solenoid off. The number of charged hadrons is measured both by counting the number of reconstructed particle hits and by forming hit doublets of pairs of layers in the pixel detector. The two methods give consistent results. The charged hadron multiplicity density dN(ch)/d eta, evaluated at eta=0 for head-on collisions, is found to be 1612 +/- 55, where the uncertainty is dominated by systematic effects. Comparisons of these results to previous measurements and to various models are also presented.