Centrality and pseudorapidity dependence of the charged-particle multiplicity density in Xe–Xe collisions at √sNN = 5.44 TeV

Abstract

In this Letter, the ALICE Collaboration presents the first measurements of the charged-particle multiplicity density, dNch/dη, and total charged-particle multiplicity, Ntotch, in Xe–Xecollisions at a centre-of-mass energy per nucleon–nucleon pair of √sNN=5.44TeV. The measurements are performed as a function of collision centrality over a wide pseudorapidity range of −3.5 <η<5. The values of dNch/dηat mid-rapidity and Ntotchfor central collisions, normalised to the number of nucleons participating in the collision (Npart) as a function of √sNNfollow the trends established in previous heavy-ion measurements. The same quantities are also found to increase as a function of Npart, and up to the 5% most central collisions the trends are the same as the ones observed in Pb–Pbat a similar energy. For more central collisions, the Xe–Xescaled multiplicities exceed those in Pb–Pbfor a similar Npart. The results are compared to phenomenological models and theoretical calculations based on different mechanisms for particle production in nuclear collisions. All considered models describe the data reasonably well within15%.