Elliptic azimuthal anisotropy of charged hadrons and neutral pions in PbPb collisions at 2.76 TeV with CMS

The elliptic flow anisotropies of charged particles and neutral pions (image) have been measured by the CMS collaboration for PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV. The second Fourier components of the anisotropic azimuthal distribution are obtained using an event-plane technique for image and four different analysis techniques for charged particles: event plane, two- and four-particle cumulants, and Lee-Yang Zeros. These techniques have different sensitivities to non-flow and flow fluctuation effects and their comparison helps disentangle hydrodynamic flow, initial state fluctuations and non-flow correlations. A comparison of the CMS measurements of image from image mesons and inclusive charged particles indicates a particle-species dependence in the azimuthal anisotropy at the LHC.