Charged-particle pseudorapidity density at mid-rapidity in p-Pb collisions at root S-NN=8.16 TeV

S. Acharya, F Acosta, D. Adamova, S Adhya, A. Adler, J Adolfsson, MM. Aggarwal, G.A. Rinella, Maria Agnello, Z. Ahammed, Shamim Ahmad, S.U. Ahn, A. Akindinov, M. Al-Turany, SN Alam, DSD Albuquerque, D. Aleksandrov, B Alessandro, R. Alfaro Molina, A. AliciA. Alkin, T. Alt, L. Altenkamper, I. Altsybeev, MN Anaam, C. Andrei, Dimosthenis Andreou, Ian Bearden, Christian Alexander Bourjau, bsm989 bsm989, rtc312 rtc312, Ante Bilandzic, Marek Chojnacki, Katarina Gajdosova, Jens Jørgen Gaardhøje, Børge Svane Nielsen, Lais Ozelin De Lima Pimentel, Freja Thoresen, You Zhou, ALICE Collaboration

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Abstract

The pseudorapidity density of charged particles, d N ch / d η, 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 d N ch / d η value is 19.1 ± 0.7 at | η| < 0.5. This quantity divided by ⟨ N part ⟩ / 2 is 4.73 ± 0.20 , where ⟨ N part ⟩ 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 d N ch / d η distribution. Saturation-based models reproduce the distributions well for η> - 1.3. The d N ch / d η 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.

OriginalsprogEngelsk
Artikelnummer307
TidsskriftEuropean Physical Journal C
Vol/bind79
Udgave nummer4
Antal sider17
ISSN1434-6044
DOI
StatusUdgivet - 1 apr. 2019

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