This paper describes the measurements of flow harmonics $v_2$–$v_6$ in $3\mu {\mathrm{b}}^{-1}$ of $\mathrm{Xe}+\mathrm{Xe}$ collisions at $\sqrt{s_{NN}}=5.44$ TeV performed using the ATLAS detector at the Large Hadron Collider (LHC). Measurements of the centrality, multiplicity, and $p_{\mathrm{T}}$ 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 $p_{\mathrm{T}}$, especially in peripheral events. Comparisons of the measured $v_n$ with measurements in $\mathrm{Pb}+\mathrm{Pb}$ collisions and $p+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=5.02$ TeV are also presented. The $v_n$ values in $\mathrm{Xe}+\mathrm{Xe}$ collisions are observed to be larger than those in $\mathrm{Pb}+\mathrm{Pb}$ 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 $\mathrm{Xe}+\mathrm{Xe}$ collisions become smaller than those in $\mathrm{Pb}+\mathrm{Pb}$ collisions. The $v_n$ in $\mathrm{Xe}+\mathrm{Xe}$ and $\mathrm{Pb}+\mathrm{Pb}$ collisions are also compared as a function of the mean number of participating nucleons, $\langle N_{\mathrm{part}}\rangle$, and the measured charged-particle multiplicity in the detector. The $v_3$ values in $\mathrm{Xe}+\mathrm{Xe}$ and $\mathrm{Pb}+\mathrm{Pb}$ collisions are observed to be similar at the same $\langle N_{\mathrm{part}}\rangle$ or multiplicity, but the other harmonics are significantly different. The ratios of the measured $v_n$ in $\mathrm{Xe}+\mathrm{Xe}$ and $\mathrm{Pb}+\mathrm{Pb}$ collisions, as a function of centrality, are also compared to theoretical calculations.

• Received 13 November 2019
• Accepted 16 December 2019

DOI:https://doi.org/10.1103/PhysRevC.101.024906

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