Correlated Event-by-Event Fluctuations of Flow Harmonics in Pb-Pb Collisions at sNN =2.76 TeV

Adam, J. and Adamová, D. and Aggarwal, M. M. and Aglieri, Rinella G. and Agnello M, M. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Bíró, Gábor and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Kiss, Gábor and Varga-Kőfaragó, Mónika and Lévai, Péter and Pochybova, Sona (2016) Correlated Event-by-Event Fluctuations of Flow Harmonics in Pb-Pb Collisions at sNN =2.76 TeV. PHYSICAL REVIEW LETTERS, 117 (18). ISSN 0031-9007

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Abstract

We report the measurements of correlations between event-by-event fluctuations of amplitudes of anisotropic flow harmonics in nucleus–nucleus collisions, obtained for the first time using a new analysis method based on multiparticle cumulants in mixed harmonics. This novel method is robust against systematic biases originating from non-flow effects and by construction any dependence on symmetry planes is eliminated. We demonstrate that correlations of flow harmonics exhibit a better sensitivity to medium properties than the individual flow harmonics. The new measurements are performed in Pb–Pb collisions at the centre-of-mass energy per nucleon pair of √sNN = 2.76 TeV by the ALICE experiment at the Large Hadron Collider (LHC). The centrality dependence of correla- tion between event-by-event fluctuations of the elliptic, v2, and quadrangular, v4, flow harmonics, as well as of anti-correlation between v2 and triangular, v3, flow harmonics are presented. The results cover two different regimes of the initial state configurations: geometry-dominated (in mid-central collisions) and fluctuation-dominated (in the most central collisions). Comparisons are made to pre- dictions from MC-Glauber, viscous hydrodynamics, AMPT and HIJING models. Together with the existing measurements of individual flow harmonics the presented results provide further constraints on initial conditions and the transport properties of the system produced in heavy-ion collisions.

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