Collective dynamics in heavy and light-ion collisions -- II) Determining the origin of collective behavior in high-energy collisions

TL;DR

This paper proposes an observable to identify whether collective behavior in high-energy ion collisions arises from hydrodynamic expansion of QGP or from final state re-scatterings, validated through kinetic theory simulations.

Contribution

It introduces a new observable to distinguish the origin of collective behavior in high-energy collisions, based on measurements from RHIC and LHC.

Findings

The observable can effectively differentiate between hydrodynamic and re-scattering mechanisms.

Validation shows the method accurately identifies the dominant process in simulated systems.

Results help clarify the physical origin of anisotropic flow in heavy-ion collisions.

Abstract

Exploiting the first measurements of the same ion species in OO collisons at RHIC and LHC, we propose an observable to distinguish whether collective behavior builds up through a hydrodynamic expansion of a strongly interacting QGP or few final state re-scatterings. Our procedure allows to disentangle the effects of the initial state geometry and the dynamical response mechanism on anisotropic flow. We validate its ability to discriminate between systems with different interaction rates using results from event-by-event simulations in kinetic theory.