Flow decorrelations in 5.44 TeV Xe+Xe collisions in ATLAS

Longitudinal decorrelations of harmonic flow $v_n$ is measured for Xe+Xe collisions at $\sqrt{s_{\mathrm{NN}}}=5.44$ TeV using the ATLAS detector at the LHC. The decorrelation signal for $v_3$ and $v_4$ is found to be nearly independent of centrality percentiles and transverse momentum ($p_{\mathrm{T}}$), but has strong centrality and $p_{\mathrm{T}}$ dependence for $v_2$. When comparing with results from Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$5.02 TeV, the decorrelation signal in mid-central collisions is found to be larger for $v_2$ but smaller for $v_3$. Current hydrodynamic models are able to describe the ratio of inclusive $v_n$ between Xe+Xe and Pb+Pb, but fail to describe the magnitudes and trends of ratio of decorrelation signal between Xe+Xe and Pb+Pb. These results provide new insights on the longitudinal structure of the initial state geometry in heavy-ion collisions.