Non-Gaussian elliptic-flow fluctuations in PbPb collisions at $\sqrt{\smash[b]{s_{_\text{NN}}}} = $ 5.02 TeV

Abstract Event-by-event fluctuations in the elliptic-flow coefficient v 2 are studied in PbPb collisions at s NN = 5.02  TeV using the CMS detector at the CERN LHC. Elliptic-flow probability distributions p ( v 2 ) for charged particles with transverse momentum 0.3 p T 3.0 GeV / c and pseudorapidity | η | 1.0 are determined for different collision centrality classes. The moments of the p ( v 2 ) distributions are used to calculate the v 2 coefficients based on cumulant orders 2, 4, 6, and 8. A rank ordering of the higher-order cumulant results and nonzero standardized skewness values obtained for the p ( v 2 ) distributions indicate non-Gaussian initial-state fluctuations. Bessel–Gaussian and elliptic power fits to the flow distributions are studied to characterize the initial-state spatial anisotropy.