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 ($\pi^0$s) 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 $\pi^0$s 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 $v_2(p_T)$ from $\pi^0$ mesons and inclusive charged particles indicates a particle-species dependence in the azimuthal anisotropy at the LHC.