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

This paper describes the measurements of flow harmonics v₂-v₆ in 3_μb^-1 of Xe + Xe collisions at √s_NN = 5.44 TeV performed using the ATLAS detector at the Large Hadron Collider (LHC). Measurements of the centrality, multiplicity, and p_T dependence of the v_n obtained using two-particle correlations and the scalar product technique are presented. The measurements are also performed using a template-fit procedure, which was developed to remove nonflow correlations in small collision systems. This nonflow 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 √s_NN = 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. The v₃ values in Xe + Xe and Pb + Pb collisions are observed to be similar at the same or multiplicity, but the other harmonics are significantly different. The ratios of the measured v_n in Xe + Xe and Pb + Pb collisions, as a function of centrality, are also compared to theoretical calculations.