Measurement of the Width and Skewness of Elliptic Flow Fluctuations in PbPb Collisions at 5.02 TeV with CMS

Flow harmonic fluctuations are studied for PbPb collisions at sNN=5.02 TeV using the CMS detector at the LHC. Flow harmonic probability distributions p(v2) are obtained by unfolding smearing effects from observed azimuthal anisotropy distributions using particles of 0.3 < pT < 3.0 GeV/c and |η| < 1.0. Cumulant flow harmonics are determined from the moments of p(v2) and used to estimate the standardized elliptic flow skewness. Hydrodynamic models predict this skewness to be negative with respect to the reaction plane. A statistically significant negative skewness is observed for all centrality bins as evidenced by a splitting between v2 {4}, v2 {6}, and v2 {8} cumulants. Elliptic power law distribution fits are made to p(v2) distributions to infer information on the nature of initial-state eccentricity distributions and found to provide a more accurate description of the fluctuations than a Bessel-Gaussian parametrization.