Characterizing flow fluctuations with moments

TL;DR

This paper introduces a comprehensive set of multiparticle correlation observables to analyze flow fluctuations in ultrarelativistic heavy-ion collisions, enabling detailed insights into the underlying physics.

Contribution

It develops a method to measure moments and mixed moments of flow distributions using two symmetric subevents, providing a new multi-pronged approach to study flow fluctuations.

Findings

Method successfully measures flow moments with rapidity gap separation.

Simulations demonstrate the ability to test non-linear hydrodynamic response.

Provides a framework for detailed flow fluctuation analysis.

Abstract

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.