Recent results on collectivity and correlations in heavy-ion collisions from ATLAS

Abstract

The measurement of the multi-particle cumulants with 0.47 $\mathrm{nb}^{-1}$ of Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV with the ATLAS detector at the LHC is presented. To investigate the impact of fluctuations arising from intrinsic centrality or volume fluctuations, the cumulants measured in two different event classes used for centrality definition are compared, one based on the total transverse energy deposited in the Forward Calorimeter and the second based on the number of charged particles reconstructed at midrapidity. In the most central collisions significant differences between two events classes are observed, and they are also present in the mid-central collisions but with smaller magnitude. Two new measurements of heavy-flavor flow are also presented. First, the production of muons from heavy-flavor decays is measured in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 2.76$ TeV using 0.14 $\mathrm{nb}^{-1}$ of data. Second, the elliptic flow of prompt and non-prompt $J/\psi$ is measured in the di-muon decay channel in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV with an integrated luminosity of 0.42 $\mathrm{nb}^{-1}$. Both measurements provide evidence for the presence of heavy-quark flow in heavy-ion collisions.