Particle production and long-range correlations in p+Pb collisions with the ATLAS detector

Abstract

The ATLAS experiment at the LHC has measured the centrality dependence of charged particle pseudorapidity distribution, charged particle spectra, and the two-particle correlations in p+Pb collisions at a nucleon-nucleon centre-of-mass energy of sqrt(s_NN)=5.02TeV. Charged particles were measured over |eta|<2.7 using the ATLAS detector tracking system. The p+Pb collision centrality was characterized by the total transverse energy deposited over the interval 3.2<eta<4.9 in the direction of the Pb-beam. Three different calculations of the number of participating nucleons, have been carried out using a standard Glauber initial state model as well as two Glauber-Gribov extensions. Charged particle multiplicities per participant pair, and the normalised charged particle spectra are found to vary in shape with eta and also with the model, pointing to the importance of the fluctuating nature of nucleon-nucleon collisions in the modelling of the initial state of p+Pb collisions. The two particle correlation exhibits flow-like modulations for all centrality intervals and particle p_T.