Measurement of the azimuthal anisotropy of charged particles produced in √sNN = 5.02 TeV Pb+Pb collisions with the ATLAS detector

Abstract

Measurements of the azimuthal anisotropy in lead–lead collisions at √sNN = 5.02 TeV are presented using a data sample corresponding to 0.49 nb⁻¹ integrated luminosity collected by the ATLAS experiment at the LHC in 2015. The recorded minimum-bias sample is enhanced by triggers for “ultra-central” collisions, providing an opportunity to perform detailed study of flow harmonics in the regime where the initial state is dominated by fluctuations. The anisotropy of the charged-particle azimuthal angle distributions is characterized by the Fourier coefficients, <i>v2–v7</i>, which are measured using the two-particle correlation, scalar-product and event-plane methods. The goal of the paper is to provide measurements of the differential as well as integrated flow harmonics vn over wide ranges of the transverse momentum, 0.5 < PT < 60 GeV, the pseudorapidity, |η| < 2.5, and the collision centrality 0–80%. Results from different methods are compared and discussed in the context of previous and recent measurements in Pb+Pb collisions at √ sNN = 2.76 TeV and 5.02 TeV. In particular, the shape of the PT dependence of elliptic or triangular flow harmonics is observed to be very similar at different centralities after scaling the <i>vn</i> and PT values by constant factors over the centrality interval 0–60% and the pT range 0.5 < PT < 5 GeV.