Speaker
Description
Data collected by the ATLAS experiment during the 2015 Pb+Pb and 2017 Xe+Xe LHC runs offer new opportunities to study charged particle azimuthal anisotropies in heavy ion collisions. This should improve the understanding of initial conditions of nuclear collisions, hydrodynamical behavior of quark-gluon plasma and parton energy loss. ATLAS measurements of differential and inclusive Fourier harmonics of charged particles ($v_n$) in 5.02 TeV Pb+Pb and 5.44 TeV Xe+Xe collisions over a wide range of transverse momenta, pseudorapidity ($|\eta|<2.5$) and collision centrality 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 dynamical properties of the QGP are studied using a modified Pearson's correlation coefficient, $\rho$, between the event-wise mean transverse momentum and the square of the flow harmonic magnitude in 5.02 TeV Pb+Pb collisions. Several important observations are made. The elliptic and triangular flow harmonics show an interesting universal mean-$p_\mathrm{T}$ scaling. A linear correlation between the $v_2$ and $v_3$ coefficients at low and high $p_\mathrm{T}$ ranges is observed and quantified. The $\rho$ coefficient is found to be negative in peripheral and positive in central Pb+Pb collisions.
