Centrality Dependence of Charged Particle Production at Large Transverse Momentum in Pb--Pb Collisions at \(\sqrt{s_{\rm{NN}}} = 2.76\) TeV

Abstract

The inclusive transverse momentum (pT) distributions of primary charged particles are measured in the pseudo-rapidity range |\(\eta\)| < 0.8 as a function of event centrality in Pb–Pb collisions at \(\sqrt{s_{NN}}\) = 2.76 TeV with ALICE at the LHC. The data are presented in the transverse momentum range 0.15 < pT < 50 GeV/c for nine centrality intervals from 70–80% to 0–5%. The Pb–Pb spectra 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. In central collisions (0–5%) the yield is most suppressed with \(R_{AA}\) around 0.13 at pT = 6–7 GeV/c. Above pT = 7 GeV/c, there is a significant rise in the nuclear modification factor, which reaches \(R_{AA}\) around 0.4 for pT > 30 GeV/c. In peripheral collisions (70–80%), the suppression is weaker with \(R_{AA}\) about 0.7 almost independent of pT. The measured nuclear modification factors are compared to other measurements and model calculations.