Multiparticle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider

Abelev, B. and Planinić, Mirko and Poljak, Nikola and Simatović, Goran and Zyzak, M. (ALICE Collaboration) (2014) Multiparticle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider. Physical Review C, 90 (5). pp. 54901-16. ISSN 0556-2813

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Abstract

Measurements of multiparticle azimuthal correlations (cumulants) for charged particles in p-Pb at √sNN√=5.02 TeV and Pb-Pb at √sNN=2.76 TeV collisions are presented. They help address the question of whether there is evidence for global, flowlike, azimuthal correlations in the p-Pb system. Comparisons are made to measurements from the larger Pb-Pb system, where such evidence is established. In particular, the second harmonic two-particle cumulants are found to decrease with multiplicity, characteristic of a dominance of few-particle correlations in p-Pb collisions. However, when a |Δη| gap is placed to suppress such correlations, the two-particle cumulants begin to rise at high multiplicity, indicating the presence of global azimuthal correlations. The Pb-Pb values are higher than the p-Pb values at similar multiplicities. In both systems, the second harmonic four-particle cumulants exhibit a transition from positive to negative values when the multiplicity increases. The negative values allow for a measurement of v2{4} to be made, which is found to be higher in Pb-Pb collisions at similar multiplicities. The second harmonic six-particle cumulants are also found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find v2{4}≃v2{6}≠0 which is indicative of a Bessel-Gaussian function for the v2 distribution. For very high-multiplicity Pb-Pb collisions, we observe that the four- and six-particle cumulants become consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and Pb-Pb are measured. These are found to be similar for overlapping multiplicities, when a |Δη|>1.4 gap is placed.

Item Type: Article
Date: November 2014
Subjects: NATURAL SCIENCES > Physics
Additional Information: Copyright (2014) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Project code: 098-0982887-2878, 119-0982887-1006
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 25 Nov 2014 11:47
Last Modified: 12 Feb 2016 16:37
URI: http://digre.pmf.unizg.hr/id/eprint/3357

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