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

Abstract

This paper describes the measurements of flow harmonics v 2 – v 6 in 3 μ b − 1 of Xe + Xe collisions at √ s N N = 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 N N = 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, ⟨ N part ⟩ , and the measured charged-particle multiplicity in the detector. The v 3 values in Xe + Xe and Pb + Pb collisions are observed to be similar at the same ⟨ N part ⟩ 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.