Centrality and pseudorapidity dependence of the charged-particle multiplicity density in Xe-Xe collisions at root s(NN)=5.44 TeV

In this Letter, the ALICE Collaboration presents the first measurements of the charged-particle multiplicity density, dN(ch)/d eta, and total charged-particle multiplicity, N-ch(tot), in Xe-Xe collisions at a centre-of-mass energy per nucleon-nucleon pair of root s(NN) = 5.44 TeV. The measurements are performed as a function of collision centrality over a wide pseudorapidity range of -3.5 < eta < 5. The values of dN(ch)/d eta at mid-rapidity and N-ch(tot) for central collisions, normalised to the number of nucleons participating in the collision (N-part) as a function of root s(NN) follow the trends established in previous heavy-ion measurements. The same quantities are also found to increase as a function of N-part, and up to the 5% most central collisions the trends are the same as the ones observed in Pb-Pb at a similar energy. For more central collisions, the Xe-Xe scaled multiplicities exceed those in Pb-Pb for a similar N-part. 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 within 15%. (C) 2018 Published by Elsevier B.V.