New measures of longitudinal decorrelation of harmonic flow

TL;DR

This paper investigates how harmonic flow decorrelates across rapidities in heavy-ion collisions, revealing that flow angle decorrelation depends on flow magnitude, and proposes experimental observables to measure this effect.

Contribution

It introduces new measures for longitudinal flow decorrelation and demonstrates their dependence on flow magnitude using hydrodynamic simulations.

Findings

Flow angle decorrelation varies with flow magnitude.

Proposed observables can experimentally measure this decorrelation.

Flow fluctuations impact rapidity-dependent flow correlations.

Abstract

Harmonic flow in relativistic heavy-ion collisions is observed in a broad range of rapidities, and the flow at different rapidities is correlated. However, fluctuations lead to a small decorrelation of the harmonic flow magnitudes and flow angles at different rapidities. Using a hydrodynamic model with Glauber Monte Carlo initial conditions we show that the flow angle decorrelation strongly depends on the flow magnitude in the event. We propose observables to measure this effect in experiment.