Recent ATLAS results on flow measurements in lead-lead and proton-lead collisions

Recent measurements from the ATLAS experiment of the azimuthal anisotropy of charged hadron production in the relativistic p+Pb and Pb+Pb collisions at the Large Hadron Collider (LHC) are presented. We report on distributions of event-by-event (EbyE) flow harmonics vn, n = 2-4, for Pb+Pb collisions at energy of sqrt(sNN)=2.76 TeV which provide a direct measure of flow harmonic fluctuations which may be related to fluctuations in the initial geometry of the interaction region. The relative EbyE elliptic flow fluctuations are compared to the measurement based on the cumulant approach as well as to the model predictions. We also report on measurements of the two-particle correlations in Delta_eta and Delta_phi as a function of pT and the transverse energy (Sum_ET^Pb ) summed over 3.1 < eta < 4.9 in the direction of the Pb beam in sqrt( sNN) = 5.02 TeV p+Pb collisions. The recoil-corrected Delta_phi-correlation exhibits flow-like modulations for all (Sum_ET^Pb ) ranges and particle pT . To study further the long-range correlations in p+Pb collisions, the elliptic flow has been measured with the cumulant approach and compared to the results from two-particle correlations. The presented p+Pb results exhibit features characteristic for collective anisotropic flow, similar to that observed in Pb+Pb collisions.