Flow phenomena in Atlas

Measurements of flow anisotropy coefficients have been performed with the ATLAS detector at the LHC, on a sample of 8 μb−1 minimum bias Pb+Pb collisions at centre-of-mass energy √sNN = 2.76 TeV and a sample of 1 μb−1 p+Pb collisions at √sNN = 5.02 TeV. The large statistics Pb+Pb sample is used to derive event-by-event distribution of v2, v3 and v4. Within uncertainties, the distributions of v3 and v4 agree with a pure Gaussian function over a wide centrality range, while significant deviations from this function are observed for v2 in mid- central and peripheral collisions. In the p+Pb sample, a long-range near-side and away-side correlation is observed for events with high transverse energy in the detector. This structure can be described by v2 anisotropy coefficients of magnitude similar to what is observed in Pb+Pb collisions.