Charged particle production in Pb-Pb and p-Pb collisions measured by the ATLAS detector

The ATLAS experiment at the Large Hadron Collider measures charged hadron spectra in Pb+Pb and p+Pb collisions. The results are compared to the p+p spectra of charged hadrons at the same centre-of-mass energy. Charged hadron distributions from Pb+Pb are compared to charged particle cross-sections in p+p collisions at $\sqrt{s}=2.76$ TeV, reference cross-section for p+Pb at $\sqrt{s_{_\text{NN}}}=5.02$ TeV is reconstructed using $\sqrt{s}=2.76$ TeV and 7 TeV p+p results. These allow for a detailed comparison of the collision systems in a wide transverse momentum and rapidity ranges in different centrality intervals. The nuclear modification factors \rPbPb\ and \rpA\ are presented as a function of centrality, $p_{_\text{T}}$, $\eta$. The charged particle \rPbPb\ are found to vary significantly as a function of transverse momentum, shows a pronounced minimum at about 7 GeV. Above 60 GeV, $R_{_\text{AA}}$ is consistent with a flat, centrality-dependent, value within the uncertainties. $R_{_\text{pPb}}$ results show strong rapidity dependence in the region of so-called Cronin peak at about 2 GeV and above $p_{_\text{T}}$ of 10 GeV show anomalous enhancement.