12-18 August 2012
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Elliptic azimuthal anisotropy of charged hadrons and neutral pions in PbPb collisions at 2.76 TeV with CMS

17 Aug 2012, 14:20


Oral Presentation Correlations and fluctuations Parallel 6D: Correlations & Fluctuations (Chair O. Evdokimov)


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.

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