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

Per-event charged particle spectra and nuclear modification factors are measured with the ATLAS detector at the LHC in p +Pb interactions at √ s_NN = 5.02 TeV. Results are presented as a function of transverse momentum, rapidity, and in different intervals of collision centrality, which is characterised in p+Pb collisions by the total transverse energy measured over the pseudorapidity interval −3.2 < η < −4.9 in the direction of the lead beam. Three different calculations of the number of nucleons participating in p +Pb collisions have been performed, assuming the Glauber model and its Glauber-Gribov Colour Fluctuation extensions. The results using different models are compared with each other, as well as with other measurements made under the same conditions and also with centrality definition based on different rapidity intervals. (paper)