Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at root s(NN)=2.76 TeV

Abstract

The inclusive transverse momentum (pT) distributions of primary charged particles are measured in the pseudo-rapidity range |η|<0.8 as a function of event centrality in Pb–Pb collisions at sNN=2.76TeV with ALICE at the LHC. The data are presented in the pT range 0.15<pT<50GeV/c for nine centrality intervals from 70–80% to 0–5%. The results in Pb–Pb are presented in terms of the nuclear modification factor RAA using a pp reference spectrum measured at the same collision energy. We observe that the suppression of high-pT particles strongly depends on event centrality. The yield is most suppressed in central collisions (0–5%) with RAA≈0.13 at pT=6–7GeV/c. Above pT=7GeV/c, there is a significant rise in the nuclear modification factor, which reaches RAA≈0.4 for pT>30GeV/c. In peripheral collisions (70–80%), only moderate suppression (RAA=0.6–0.7) and a weak pT dependence is observed. The measured nuclear modification factors are compared to other measurements and model calculations.