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

Aad, G., Abbott, B., Abdallah, J., Abdinov, O., Abeloos, B., Aben, R., et al. (2016). Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in sNN=5.02 TeV p + Pb collisions measured by the ATLAS experiment. PHYSICS LETTERS. SECTION B, 763, 313-336 [10.1016/j.physletb.2016.10.053].

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

F. Ceradini;B. Di Micco;R. Di Nardo;D. Orestano;F. Petrucci;D. Puddu;