Energy dependence and uctuations of anisotropic ow in Pb-Pb collisions at √sNN = 5.02 and 2.76 TeV

Abstract

Measurements of anisotropic ow coe cients with two- and multi-particle cumulants for inclusive charged particles in Pb{Pb collisions at p sNN = 5:02 and 2.76TeV are reported in the pseudorapidity range j j < 0:8 and transverse momentum 0:2 < pT < 50 GeV/c. The full data sample collected by the ALICE detector in 2015 (2010), corresponding to an integrated luminosity of 12.7 (2.0) bð€€€1 in the centrality range 0{80%, is analysed. Flow coe cients up to the sixth ow harmonic (v6) are reported and a detailed comparison among results at the two energies is carried out. The pT dependence of anisotropic ow coe cients and its evolution with respect to centrality and harmonic number n are investigated. An approximate power-law scaling of the form vn(pT) pn=3 T is observed for all ow harmonics at low pT (0:2 < pT < 3 GeV/c). At the same time, the ratios vn=vn=m m are observed to be essentially independent of pT for most centralities up to about pT = 10 GeV/c. Analysing the di erences among higher-order cumulants of elliptic ow (v2), which have di erent sensitivities to ow uctuations, a measurement of the standardised skewness of the event-by-event v2 distribution P(v2) is reported and constraints on its higher moments are provided. The Elliptic Power distribution is used to parametrise P(v2), extracting its parameters from ts to cumulants. The measurements are compared to di erent model predictions in order to discriminate among initial-state models and to constrain the temperature dependence of the shear viscosity to entropy-density ratio.