Collision system and beam energy dependence of anisotropic flow fluctuations

TL;DR

This paper investigates how flow fluctuations in heavy-ion collisions depend on system size, shape, and energy, providing insights into initial-state effects and aiding the extraction of shear viscosity.

Contribution

It presents new measurements of elliptic flow fluctuations across different collision systems and energies, emphasizing the role of initial-state fluctuations.

Findings

Flow fluctuations depend on event shape, system size, and beam energy.

Initial-state-driven fluctuations dominate the observed flow variability.

Results can constrain initial-state models and improve shear viscosity estimates.

Abstract

New measurements of two- and four-particle elliptic flow are used to investigate flow fluctuations in collisions of U+U at $\sqrt{s_{NN}}$ = 193~GeV, Cu+Au at $\sqrt{s_{NN}}$ = 200~GeV and Au+Au at several beam energies. These measurements highlight the dependence of these fluctuations on the event-shape, system-size and beam energy and indicate a dominant role for initial-state-driven fluctuations. These measurements could provide further constraints for initial-state models, as well as for precision extraction of the temperature-dependent specific shear viscosity $\frac{\eta}{s}(T)$.