Speaker
Krisztian Krajczar
(MIT)
Description
The nuclear modification factor R_AA is one of the key signatures for the energy loss of fast partons traversing a QCD medium. Charged particle transverse momentum (pT) spectra have been measured by CMS for pp and PbPb collisions at the same collision energy per nucleon pairs, sqrt(s_(NN))=2.76 TeV, corresponding to integrated luminosities of 230 nb-1 and 150 ub-1, respectively. Calorimeter-based high-transverse-energy jet triggers are employed to enhance the statistical reach of the high-pT measurements. The pp results are compared to various generator tunes and also to an empirical scaling of different collision energies with xT=2pT/sqrt(s) over the pT range up to 100 GeV/c. We have obtained R_AA 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 roughly a factor of 2 for particles with pT = 40 - 100 GeV/c.
Primary author
Krisztian Krajczar
(MIT)
