Pseudorapidity distributions of charged hadrons in xenon-xenon collisions at $\sqrt{s_\mathrm{NN}} =$ 5.44 TeV

Bakhshiansohi, Hamed [UCL] Bondu, Olivier [UCL] Brochet, Sébastien [UCL] Bruno, Giacomo [UCL] Caputo, Claudio [UCL] David, Pieter [UCL] Delaere, Christophe [UCL] Delcourt, Martin [UCL] Francois, Brieuc [UCL] Giammanco, Andrea [UCL] Krintiras, Georgios [UCL] Lemaitre, Vincent [UCL] Magitteri, Alessio [UCL] Mertens, Alexandre [UCL] Musich, Marco [UCL] Piotrzkowski, Krzysztof [UCL] Saggio, Alessia [UCL] Vidal Marono, Miguel [UCL] Wertz, Sébastien [UCL] Zobec, Joze [UCL] CMS Collaboration et al.

Measurements of the pseudorapidity distributions of charged hadrons produced in xenon-xenon collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_\mathrm{NN}} =$ 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 $|\eta|$ $<$ 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 $|\eta|$ $<$ 0.5 is found to be 1187 $\pm$ 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.