Centrality dependence of the nuclear modification factor of charged pions, kaons, and protons in Pb-Pb collisions at √sNN = 2.76 TeV

Abstract

Transverse momentum (pT) spectra of pions, kaons, and protons up to pT = 20 GeV/c have been measured in Pb-Pb collisions at √sNN = 2.76 TeV using the ALICE detector for six different centrality classes covering 0%–80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at pT ≈ 3 GeV/c in central Pb-Pb collisions that decreases for more peripheral collisions. For pT > 10 GeV/c, the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10%–20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched jet. For pT < 10 GeV/c, the data provide important constraints for models aimed at describing the transition from soft to hard physics.