Measurement of Charged-Particle Spectra in Pb + Pb Collisions at √s̅{n̅n̅} = 2.76 TeV with the ATLAS Detector at the LHC

Charged-particle spectra obtained in Pb+Pb interactions at √s̅{̅N̅N̅}̅ = 2.76 TeV and pp interactions at √s̅{̅N̅N̅}̅ = 2.76 TeV with the ATLAS detector at the LHC are presented, using data with integrated luminosities of 0.15 nb⁻¹ and 4.2 pb⁻¹, respectively, in a wide transverse momentum (0.5 < p{T} < 150 GeV) and pseudorapidity (|η| < 2) range. For Pb+Pb collisions, the spectra are presented as a function of collision centrality, which is determined by the response of the forward calorimeters located on both sides of the interaction point. The nuclear modification factors R{AA} and R{CP} are presented in detail as a function of centrality, p{T} and η. They show a distinct p{T}-dependence with a pronounced minimum at about 7 GeV. Above 60 GeV, R{AA} is consistent with a plateau at a centrality-dependent value, within the uncertainties. The value is 0.55 ± 0.01(stat.) ± 0.04(syst.) in the most central collisions. The R{AA} distribution is consistent with flat |η| dependence over the whole transverse momentum range in all centrality classes.