Characterizing flow fluctuations with moments

We present a complete set of multiparticle correlation observables for ultrarelativistic heavy- ion collisions. These include moments of the distribution of the anisotropic flow in a single harmonic and also mixed moments, which contain the information on correlations between event planes of different harmonics. We explain how all these moments can be measured using just two symmetric subevents separated by a rapidity gap. This presents a multi- pronged probe of the physics of flow fluctuations. For instance, it allows to test the hypothesis that event- plane correlations are generated by non- linear hydrodynamic response. We illustrate the method with simulations of events in A MultiPhase Transport (AMPT) model. (C) 2015 The Authors. Published by Elsevier B.V.