Azimuthal Anisotropy in Heavy-ion Collisions with the ATLAS Detector at the LHC

The high-statistics experimental data collected by the ATLAS experiment during the 2015 Pb+Pb and 2017 Xe+Xe LHC runs are used to measure charged particle azimuthal anisotropy. ATLAS measurements of differential and global Fourier harmonics of charged particles ($\nu_n$) in 5.02 TeV Pb+Pb and 5.44 TeV collisions in a wide range of transverse momenta (up to 60 GeV), pseudorapidity ($\left| \eta \right | < 2:5$) and collision centrality (0–80%) are presented. The higher order harmonics, sensitive to fluctuations in the initial state, are measured up to $n = 7$ using the two-particle correlation, cumulant and scalar-product methods. The dynamic properties of the QGP are studied using a modified Pearson’s correlation coefficient, $\rho(\nu_n p_T)$, between the eventwise mean transverse momentum and the magnitude of the flow vector in 5.02 TeV Pb+Pb and p+Pb collisions. The flow results allow to improve the understanding of initial conditions of nuclear collisions, hydrodynamical behaviour of Quark–Gluon Plasma and parton energy loss.