Azimuthal anisotropy in Pb+Pb, Xe+Xe and p+Pb collisions and vn–pt correlations in Pb+Pb and p+Pb collisions with the ATLAS experiment

Abstract

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 (up to 60 GeV), pseudorapidity ($|\eta|<2.5$) and collision centrality (0-80\%) are presented. The higher order harmonics, sensitive to fluctuations in the initial state, are measured up to $n$ = 5 using the two-particle correlation, cumulant and scalar-product methods. The flow results allow to improve the understanding of initial conditions of nuclear collisions, hydrodynamical behaviour of quark-gluon plasma (QGP) and parton energy loss. The dynamic properties of the QGP can also be studied using a modified Pearson's correlation coefficient, $\rho(v_n,p_\mathrm{T})$, that quantifies correlation between the mean transverse momentum and the magnitude of the flow vector. The $\rho$ coefficient is presented for 5.02 TeV Pb+Pb and $p$+Pb collisions. Azimuthal anisotropy in Pb+Pb collisions is also compared with new measurements in $pp$ and $p$+Pb collisions.