Measurement of charged-particle spectra in Pb+Pb collisions at $\sqrt{{s}_\mathsf{{NN}}} = 2.76$ TeV with the ATLAS detector at the LHC

Charged-particle spectra obtained in Pb+Pb interactions at $ \sqrt{s_{\mathrm{NN}}}=2.76 $ TeV and pp interactions at $ \sqrt{s_{\mathrm{NN}}}=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.