Anisotropic flow and flow fluctuations of identified hadrons in Pb–Pb collisions at √s_NN = 5.02 TeV

The first measurements of elliptic flow of π^±, K^±, p+p̅, K⁰_S , Λ+Λ̅, ϕ, Ξ⁻+Ξ̅⁺, and Ω⁻+Ω̅⁺ using multiparticle cumulants in Pb–Pb collisions at √s_NN = 5.02 TeV are resented. Results obtained with two- (v₂{2}) and four-particle cumulants (v2{4}) are shown as a function of transverse momentum, p_T, for various collision centrality intervals. Combining the data for both v₂{2} and v₂{4} also allows us to report the first measurements of the mean elliptic flow, elliptic flow fluctuations, and relative elliptic flow fluctuations for various hadron species. These observables probe the event-by-event eccentricity fluctuations in the initial state and the contributions from the dynamic evolution of the expanding quark–gluon plasma. The characteristic features observed in previous p_T-differential anisotropic flow measurements for identified hadrons with two-particle correlations, namely the mass ordering at low p_T and the approximate scaling with the number of constituent quarks at intermediate p_T, are similarly present in the four-particle correlations and the combinations of v₂{2} and v₂{4}. In addition, a particle species dependence of flow fluctuations is observed that could indicate a significant contribution from final state hadronic interactions. The comparison between experimental measurements and CoLBT model calculations, which combine the various physics processes of hydrodynamics, quark coalescence, and jet fragmentation, illustrates their importance over a wide p_T range.