Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in sNN=5.02 TeV p + Pb collisions measured by the ATLAS experiment

Abstract

Measurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using p +Pbcollision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of √sNN=5.02 TeV. Charged particles are reconstructed over pseudorapidity |η| <2.3and transverse momentum between 0.1GeVand 22GeVin a dataset corresponding to an integrated luminosity of 1μb−1. The results are presented in the form of charged-particle nuclear modification factors, where the p +Pbcharged-particle multiplicities are compared between central and peripheral p +Pbcollisions as well as to charged-particle cross sections measured in ppcollisions. The p +Pbcollision centrality is characterized by the total transverse energy measured in −4.9<η<−3.1, which is in the direction of the outgoing lead beam. Three different estimations of the number of nucleons participating in the p +Pbcollision are carried out using the Glauber model and two Glauber–Gribov colour-fluctuation extensions to the Glauber model. The values of the nuclear modification factors are found to vary significantly as a function of rapidity and transverse momentum. Abroad peak is observed for all centralities and rapidities in the nuclear modification factors for charged-particle transverse momentum values around 3GeV. The magnitude of the peak increases for more central collisions as well as rapidity ranges closer to the direction of the outgoing lead nucleus.