Measurement of the azimuthal anisotropy of charged particles in 5.02 TeV Pb+Pb and 5.44 TeV Xe+Xe collisions with ATLAS

The 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 anisotropy. The high-statistics Pb+Pb sample allows for a detailed study of the azimuthal anisotropy of produced particles. This should improve the understanding of initial conditions of nuclear collisions, hydrodynamical behavior of quark-gluon plasma and parton energy loss. New ATLAS measurements of differential and global Fourier harmonics of charged particles ($v_n$) in 5.02 TeV Pb+Pb and 5.44 TeV Xe+Xe collisions in 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 dynamic properties of QGP are studied using a recently-proposed modified Pearson's correlation coefficient, $\rho(v^2_n,p_\mathrm{T})$, between the eventwise mean transverse momentum and the magnitude of the flow vector in 5.02 TeV Pb+Pb and p+Pb collisions. Several important observations are made. The elliptic and triangular flow harmonics show an interesting universal $p_\mathrm{T}$-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 correlation coefficient for $v_2$ is found to be negative in peripheral and positive in central Pb+Pb collisions. The value for $v_3$ is found to be much smaller than for $v_2$ and have similar centrality behavior as the $v_2$