Pseudorapidity distributions of charged hadrons in xenon-xenon collisions at sqrt(s_NN) = 5.44 TeV

Measurements of the pseudorapidity distributions of charged hadrons produced in xenon-xenon collisions at a nucleon-nucleon centre-of-mass energy of sNN 5.44 TeV are presented. The measurements are based on data collected by the CMS experiment at the LHC. The yield of primary charged hadrons produced in xenon-xenon collisions in the pseudorapidity range η < 3.2 is determined using the silicon pixel detector in the CMS tracking system. For the 5% most central collisions, the charged- hadron pseudorapidity density in the midrapidity region η < 0.5 is found to be 1187 36 (syst), with a negligible statistical uncertainty. The rapidity distribution of charged hadrons is also presented in the range y < 3.2 and is found to be independent of rapidity around y 0. Existing Monte-Carlo event generators are unable to simultaneously describe both results. Comparisons of charged-hadron multiplicities between xenon-xenon and lead-lead collisions at similar collision energies show that particle production at midrapidity is strongly dependent on the collision geometry in addition to the system size and collision energy.