Pseudorapidity distributions of charged hadrons in xenon-xenon collisions at sNN=5.44 TeV

Abstract Measurements of the pseudorapidity distributions of charged hadrons produced in xenon-xenon collisions at a nucleon-nucleon centre-of-mass energy of s NN = 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.