Factorization breaking for higher moments of harmonic flow

TL;DR

This paper investigates how correlations between harmonic flow vectors at different transverse momenta break factorization, providing new methods to measure flow properties and compare with experimental data in heavy-ion collisions.

Contribution

It introduces novel four-particle correlators dependent on transverse momentum to independently measure flow vector, magnitude, and angle factorization breaking coefficients.

Findings

Comparison with ALICE data shows good agreement.

Predictions for momentum-dependent flow factorization breaking.

Correlators can reveal initial state fluctuations and collision dynamics.

Abstract

We study correlations between harmonic flow vectors squared measured at different transverse momenta. One of the flow harmonics squared is taken at a fixed transverse momentum and correlated to the momentum averaged harmonic flow squared of the same order. Such four particle correlators, dependent on transverse momentum, have been recently measured experimentally. Factorization coefficients based on the ratio of such four-particle correlators allow the independent measurement of the flow vector and flow magnitude factorization breaking coefficient. Moreover, the correlation of the angles of flow harmonics as a function of transverse momentum can be extracted. Results are compared to preliminary data of the ALICE Collaboration. We also present predictions for the momentum dependent factorization breaking coefficient between mixed flow harmonics. The correlators with squares of mixed harmonics can serve as a way to independently measure the flow vector, flow magnitude, and flow angle correlations, and could be used to gain additional information on the fluctuating initial state and the dynamics in heavy-ion collisions.