Multiplicity dependence of the average transverse momentum in pp, p-Pb, and Pb-Pb collisions at the LHC

Abstract

The average transverse momentum <\(p_T\)> versus the charged-particle multiplicity \(N_{ch}\) was measured in p-Pb collisions at a collision energy per nucleon-nucleon pair \(\sqrt{s_{NN}}\) = 5.02 TeV and in pp collisions at collision energies of \(\sqrt{s}\) = 0.9, 2.76, and 7 Tev in the kinematic range 0.15 < \(p_T\) < 10.0 Gev/c and |\(\eta\)| < 0.3 with the ALICE apparatus at the LHC. These data are compared to results in Pb-Pb collisions at \(\sqrt{s_{NN}}\) = 2.76 Tev at similar charged-particle multiplicities. In pp and p-Pb collisions, a strong increase of <\(p_T\)> with \(N_{ch}\) is observed, which is much stronger than that measured in Pb-Pb collisions. For pp collisions, this could be attributed, within a model of hadronizing strings, to multiple-parton interactions and to a final-state color reconnection mechanism. The data in p-Pb and Pb-Pb collisions cannot be described by an incoherent superposition of nucleon-nucleon collisions and pose a challenge to most of the event generators.