Measurement of charged particle R_AA at high pT in PbPb collisions at sqrt(sNN)=2.76 TeV with CMS

TL;DR

This study measures the suppression of high transverse momentum charged particles in PbPb collisions at 2.76 TeV, revealing significant suppression at moderate pT that diminishes at higher pT, indicating jet quenching effects in quark-gluon plasma.

Contribution

First CMS measurement of charged particle R_AA at high pT in PbPb collisions at 2.76 TeV, utilizing calorimeter-based triggers for extended high-pT range.

Findings

Charged particle yield is suppressed by up to a factor of 7 at pT = 5-10 GeV/c in central collisions.

Suppression decreases to about a factor of 2 at pT = 40-100 GeV/c.

High-pT suppression pattern provides insights into parton energy loss in quark-gluon plasma.

Abstract

Charged particle transverse momentum (pT) spectra have been measured by CMS for pp and PbPb collisions at the same sqrt(sNN)=2.76 TeV collision energy per nucleon pairs. Calorimeter-based jet triggers are employed to enhance the statistical reach of the high-pT measurements. The nuclear modification factor (R_AA) is obtained in bins of collision centrality for the PbPb data sample dividing by the measured pp reference spectrum. In the range pT = 5-10 GeV/c, the charged particle yield in the most central PbPb collisions is suppressed by up to a factor of 7. At higher pT, this suppression is significantly reduced, approaching a factor of 2 for particles with pT = 40-100 GeV/c.