Measurement of charged particle R[subscript AA] at high p[subscript T] in PbPb collisions at √s[subscript NN] = 2.76 TeV with CMS

Abstract

Charged particle transverse momentum (p[subscript T]) spectra have been measured by CMS for pp and PbPb collisions at the same √sNN = 2.76 TeV collision energy per nucleon pairs. Calorimeter-based jet triggers are employed to enhance the statistical reach of the high-p[subscript T] measurements. The nuclear modification factor (R[subscript AA]) is obtained in bins of collision centrality for the PbPb data sample dividing by the measured pp reference spectrum. In the range p[subscript T] = 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 p[subscript T], this suppression is significantly reduced, approaching a factor of 2 for particles with p[subscript T] = 40 – 100 GeV.