Centrality and pseudorapidity dependence of the charged-particle multiplicity density in Xe-Xe collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.44 TeV

Abstract

In this Letter, the ALICE Collaboration presents the first measurements of the charged-particle multiplicity density, $\mathrm{d}{\mathrm{N}}_{\mathrm{ch}}/\mathrm{d}\eta$, and total charged-particle multiplicity, $N_{\mathrm{ch}}^{\mathrm{tot}}$, in Xe-Xe collisions at a centre-of-mass energy per nucleon--nucleon pair of $\sqrt{s_{\mathrm{NN}}}$ = 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 $\mathrm{d}{\mathrm{N}}_{\mathrm{ch}}/\mathrm{d}\eta$ at mid-rapidity and $N_{\mathrm{ch}}^{\mathrm{tot}}$ for central collisions, normalised to the number of nucleons participating in the collision ($N_{\mathrm{part}}$) as a function of $\sqrt{s_{\mathrm{NN}}}$, follow the trends established in previous heavy-ion measurements. The same quantities are also found to increase as a function of $N_{\mathrm{part}}$, 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 $N_{\mathrm{part}}$. 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%.

25 pages, 7 captioned figures, 1 table, authors from page 20, published, figures at http://aliceinfo.cern.ch/ArtSubmission/node/4293