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

Event-by-event fluctuations in the elliptic-flow coefficient $v_2$ are studied in PbPb collisions at $\sqrt{s_{{}_{\text{NN}}}}=$ 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 $<p_{\mathrm{T}}<$ 3.0 GeV and pseudorapidity $\mathrm{\mid }\eta \mathrm{\mid }<$ 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 fluctuation behavior. Bessel-Gaussian and elliptic power fits to the flow distributions are studied to characterize the initial-state spatial anisotropy.