Flow and centrality fluctuations from ATLAS

Results of multi-particle cumulants for harmonic flow coefficients $v_n$ are obtained for Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. The cumulant ratios $v_n\{4\}/v_n\{2\}$ for $n=2$,3 and 4 and $v_2\{6\}/v_2\{4\}$ show centrality-dependent behavior compatible with eccentricity fluctuations. However significant $\pT$ dependences of these cumulants suggesting flow fluctuations may also arise from final-state interactions. The flow cumulants are also observed to depend on the resolution of the quantity used to define event centrality: poorer centrality resolution tends to increase the value of $v_2\{2\}$ and changes the sign of $v_2\{4\}$ and $v_3\{4\}$ in ultra-central collisions. These results shed light on the contributions of flow fluctuations from the initial state and the final state, as well as the influence of centrality fluctuations.