The first measurement of longitudinal decorrelations of harmonic flow amplitudes vn for n=2, 3 and 4 in Xe+Xe collisions at √sNN=5.44 TeV is obtained using 3~μb−1 of data with the ATLAS detector at the LHC. The decorrelation signal for v3 and v4 is found to be nearly independent of collision centrality and transverse momentum (pT) requirements on final-state particles, but for v2 a strong centrality and pT dependence is seen. When compared with the results from Pb+Pb collisions at √sNN=5.02 TeV, the longitudinal decorrelation signal in mid-central Xe+Xe collisions is found to be larger for v2, but smaller for v3. Current hydrodynamic models reproduce the ratios of the vn measured in Xe+Xe collisions to those in Pb+Pb collisions but fail to describe the magnitudes and trends of the ratios of longitudinal flow decorrelations between Xe+Xe and Pb+Pb. These results provide new insights into the longitudinal structure of the initial-state geometry in heavy-ion collisions.
Bibliographical noteNot yet published as of 10/03/2021.
29 pages in total, author list starting page 13, 4 figures, submitted to Phys. Rev. Lett. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2019-06/