Measurement of high-pt azimuthal anisotropy in charged hadron production from 2.76 TeV PbPb collisions at CMS

The CMS experiment has measured the azimuthal anisotropy of charged hadrons over a very broad transverse-momentum range in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 $TeV$ and for multiple collision centralities. The second order Fourier coefficient, $v_{2}$, is extracted by correlating charged tracks with the event plane reconstructed using the energy deposited in the forward-angle calorimeters. Utilizing the broad coverage of the CMS calorimetry at the very forward region, contamination from back-to-back dijets is significantly suppressed. The observed azimuthal anisotropy in the high-pt regime provides important constraints on the path-length dependence of parton energy loss.