Flow and centrality fluctuations from ATLAS

Results of multi-particle cumulants for harmonic flow coefficients ν_n are obtained in s_NN=5.02TeV Pb+Pb collisions with the ATLAS detector at the Large Hadron Collider. The cumulant ratios ν_n{4}/ν_n{2} for n = 2, 3 and 4 and ν₂{6}/ν₂{4} show centrality-dependent behavior compatible with eccentricity fluctuations. However, significant dependences on transverse momentum are observed, suggesting that flow fluctuations may also arise from final-state interactions. The flow cumulants are also found to depend on the resolution of the quantity used to define event centrality: poorer centrality resolution tends to increase the value of ν₂{2} and changes the sign of ν₂{4} and ν₃{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 on the influences of centrality fluctuations.