Abstract
The azimuthal anisotropy of charged particles in Pb-Pb collisions at is measured with the CMS detector at the LHC over an extended transverse momentum () range up to approximately . The data cover both the low- region associated with hydrodynamic flow phenomena and the high- region where the anisotropies may reflect the path-length dependence of parton energy loss in the created medium. The anisotropy parameter () 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 values are found to first increase with , reaching a maximum around , and then to gradually decrease to almost zero, with the decline persisting up to at least over the full centrality range measured.
- Received 9 April 2012
DOI:https://doi.org/10.1103/PhysRevLett.109.022301
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© 2012 CERN, for the CMS Collaboration