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

The average transverse momentum pT versus the charged-particle multiplicity Nch was measured in p–Pb collisions at a collision energy per nucleon–nucleon pair √sNN=5.02 TeV and in pp collisions at collision energies of √s=0.9,2.76, and 7 TeV in the kinematic range 0.15<pT<10.0 GeV/c and |η|<0.3 with the ALICE apparatus at the LHC. These data are compared to results in Pb–Pb collisions at √sNN=2.76 TeV at similar charged-particle multiplicities. In pp and p–Pb collisions,a strong increase of pT with Nch 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.