Centrality dependence of particle production in p-Pb collisions at √sNN = 5.02 TeV

Adam, J. and Planinić, Mirko and Poljak, Nikola and Simatović, Goran and Utrobičić, Antonija and Zyzak, M. (ALICE Collaboration) (2015) Centrality dependence of particle production in p-Pb collisions at √sNN = 5.02 TeV. Physical Review C, 91 (6). pp. 64905-11. ISSN 0556-2813

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Abstract

We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at √sNN = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (N_part) or the number of nucleon-nucleon binary collisions (N_coll) are described. We show that, in contrast to Pb-Pb collisions, in p-Pb collisions large multiplicity fluctuations together with the small range of participants available generate a dynamical bias in centrality classes based on particle multiplicity. We propose to use the zero-degree energy, which we expect not to introduce a dynamical bias, as an alternative event-centrality estimator. Based on zero-degree energy-centrality classes, the N_part dependence of particle production is studied. Under the assumption that the multiplicity measured in the Pb-going rapidity region scales with the number of Pb participants, an approximate independence of the multiplicity per participating nucleon measured at mid-rapidity of the number of participating nucleons is observed. Furthermore, at high-p_T the p-Pb spectra are found to be consistent with the pp spectra scaled by Ncoll for all centrality classes. Our results represent valuable input for the study of the event-activity dependence of hard probes in p-Pb collisions and, hence, help to establish baselines for the interpretation of the Pb-Pb data.

Item Type: Article
Date: 8 June 2015
Subjects: NATURAL SCIENCES > Physics > Nuclear Physics
Additional Information: Copyright (2015) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 11 Jun 2015 10:33
Last Modified: 11 Jun 2015 10:33
URI: http://digre.pmf.unizg.hr/id/eprint/4042

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