Eric Andrew Appelt (Vanderbilt University (US))
The elliptic flow anisotropies of charged particles and neutral pions (pi0s) 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 pi0s 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. The results are presented as a function of pT, pseudorapidity, and centrality. A comparison of the CMS measurements of v2(pT) from pi0 mesons and inclusive charged particles reveals a systematic difference in the range of pT = 2.5 ~ 5 GeV/c, with the neutral pion anisotropies being weaker than those observed for inclusive charged particles. This difference indicates a particle-species dependence in the azimuthal anisotropy at the LHC. New measurements of correlations associated with mixed harmonics for charged particles are explored and discussed in terms of participant fluctuations. A systematic comparison of the LHC results to lower energy observations will also be presented.
Collaboration CMS (CERN)