Two-particle correlations in p-p and Pb-Pb collisions with the ATLAS detector at the LHC

An overview of two angular correlation analyses with the ATLAS detector at the LHC are presented. Two-particle correlations are measured in proton-proton collisions at two centre-of-mass energies, ps = 0.9 and 7 TeV, recorded in the beginng of LHC beam operation in 2009 and 2010. A kinematic range is defined for these measurements considering primary charged particles with a transverse momentum of pT > 100 MeV and a pseudorapidity of |h| < 2.5. The results are corrected for detector effects and compared to several Monte-Carlo models including tunes of PYTHIA6, PYTHIA8 and PHOJET. In lead-lead collisions, particle correlations are analysed by measuring flow components of the azimuthal angular distribution. Measurements of the “medium”, created in such ultra-relativistic heavy ion collisions at psNN = 2.76 TeV as in 2010, provide significant constraints for modeling its dynamical evolution. The results of the analysis of the v2-component, also known as ellliptic flow, cover a pT -range from pT = 0.5 to 20 GeV and as well |h| < 2.5. Higher order flow components are also presented.