Azimuthal anisotropy of charged particles at high transverse momenta in Pb-Pb collisions at √sNN=2.76TeV

Abstract

The azimuthal anisotropy of charged particles in Pb-Pb collisions at √sNN=2.76 TeV is measured with the CMS detector at the LHC over an extended transverse momentum (pT) range up to approximately 60 GeV/c. The data cover both the low-pT region associated with hydrodynamic flow phenomena and the high-pT region where the anisotropies may reflect the path-length dependence of parton energy loss in the created medium. The anisotropy parameter (v2) of the particles is extracted by correlating charged tracks with respect to the event-plane reconstructed by using the energy deposited in forward-angle calorimeters. For the six bins of collision centrality studied, spanning the range of 0?60% most-central events, the observed v2 values are found to first increase with pT, reaching a maximum around pT=3GeV/c, and then to gradually decrease to almost zero, with the decline persisting up to at least pT=40GeV/c over the full centrality range measured.