Charged-particle pseudorapidity density at mid-rapidity in p–Pb collisions at √sNN = 8.16 TeV
Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Clemens; Adolfsson, Jonatan; Aggarwal, Madan M.; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Ahammed, Zubayer; Alme, Johan; Altenkaemper, Lucas; Djuvsland, Øystein; Ersdal, Magnus Rentsch; Fionda, Fiorella Maria Celeste; Nystrand, Joakim; Rehman, Attiq ur; Røhrich, Dieter; Tambave, Ganesh Jagannath; Ullaland, Kjetil; Wagner, Boris; Yuan, Shiming; Zhou, Zhuo; Arsene, Ionut Cristian; Bätzing, Paul Christoph; Dordic, Olja; Lardeux, Antoine Xavier; Lindal, Svein; Mahmood, Sohail Musa; Malik, Qasim Waheed; Richter, Matthias; Røed, Ketil; Skaali, Toralf Bernhard; Tveter, Trine Spedstad; Wikne, Jon Christopher; Zhao, Chengxin; Helstrup, Håvard; Hetland, Kristin Fanebust; Kileng, Bjarte; Nesbø, Simon Voigt; Storetvedt, Maksim Melnik; Langøy, Rune; Lien, Jørgen André; Ahmad, Shafiq F.; Ahn, Sang Un; Aiola, Salvatore; Akindinov, Alexander; Al-Turany, Mohammed; Alam, Sk Noor; De Albuquerque, Danilo Silva; ALICE, Collaboration
Peer reviewed, Journal article
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The pseudorapidity density of charged particles, dNch/dη , in p–Pb collisions has been measured at a centre-of-mass energy per nucleon–nucleon pair of sNN−−−√ = 8.16 TeV at mid-pseudorapidity for non-single-diffractive events. The results cover 3.6 units of pseudorapidity, |η|<1.8 . The dNch/dη value is 19.1±0.7 at |η|<0.5 . This quantity divided by ⟨Npart⟩ / 2 is 4.73±0.20 , where ⟨Npart⟩ is the average number of participating nucleons, is 9.5% higher than the corresponding value for p–Pb collisions at sNN−−−√ = 5.02 TeV. Measurements are compared with models based on different mechanisms for particle production. All models agree within uncertainties with data in the Pb-going side, while HIJING overestimates, showing a symmetric behaviour, and EPOS underestimates the p-going side of the dNch/dη distribution. Saturation-based models reproduce the distributions well for η>−1.3 . The dNch/dη is also measured for different centrality estimators, based both on the charged-particle multiplicity and on the energy deposited in the Zero-Degree Calorimeters. A study of the implications of the large multiplicity fluctuations due to the small number of participants for systems like p–Pb in the centrality calculation for multiplicity-based estimators is discussed, demonstrating the advantages of determining the centrality with energy deposited near beam rapidity.