Measurement of the azimuthal anisotropy of charged-particle production in Xe+Xe collisions at 5.44 TeV with the ATLAS detector*

This talk describes the measurements of flow harmonics $v_2$--$v_6$ in Xe+Xe collisions at 5.44 TeV performed using the ATLAS detector at the LHC. Measurements of the centrality, multiplicity and $p_T$ dependence of the $v_n$ obtained using two-particle correlations and the scalar product technique will be presented. The measurements are also performed using a template-fit procedure, which was developed to remove non-flow correlations in small collision systems. This non-flow removal is shown to have a significant influence on the measured $v_n$ at high $p_T$, especially in peripheral events. Comparisons of the measured $v_n$ with measurements in Pb+Pb collisions and p+Pb collisions at 5.02 TeV are also presented. The $v_n$ values in Xe+Xe collisions are observed to be larger than those in Pb+Pb collisions for $n=2$, 3 and 4 in the most central events. However, with decreasing centrality or increasing harmonic order $n$, the $v_n$ values in Xe+Xe collisions become smaller than those in Pb+Pb collisions. The $v_n$ in Xe+Xe and Pb+Pb collisions are also compared as a function of the mean number of participating nucleons and the measured charged-particle multiplicity in the detector. Comparisons of the $v_n$ measurements with theoretical calculations will also be shown.