Centrality and pT dependence of charged particle RAA in PbPb collisions at sqrt(sNN) = 2.76 TeV

TL;DR

This paper measures the transverse momentum spectra of charged particles in PbPb collisions at 2.76 TeV, analyzing how centrality affects the nuclear modification factor RAA and comparing results to theoretical models.

Contribution

It provides the first detailed measurement of RAA as a function of pT and centrality at this energy, using CMS data and a novel interpolation method for the pp reference spectrum.

Findings

RAA varies with collision centrality and pT.

Measured RAA in the most central collisions shows suppression consistent with energy loss models.

Comparison with theoretical predictions helps constrain models of parton energy loss.

Abstract

The transverse momentum pT spectra of charged particles is measured by CMS as a function of collision centrality in PbPb collisions at sqrt(sNN) = 2.76 TeV. The results are compared to a pp reference spectrum, constructed by interpolation between sqrt(s) = 0.9 and 7 TeV measurements. The nuclear modification factor RAA is constructed by dividing the PbPb pT spectrum, normalized to the number of binary collisions (Ncoll), by the pp spectrum. Measured RAA in 0-5% centrality bin is compared to several theoretical predictions.