Influence of a temperature-dependent shear viscosity on the azimuthal asymmetries of transverse momentum spectra in ultrarelativistic heavy-ion collisions

TL;DR

This study examines how a temperature-dependent shear viscosity affects azimuthal flow asymmetries and transverse momentum spectra in ultrarelativistic heavy-ion collisions, highlighting the importance of viscosity near the QCD transition.

Contribution

It provides a detailed analysis of the effects of temperature-dependent shear viscosity and initial conditions on flow asymmetries across different energies and centralities.

Findings

Hadronic viscosity dominates elliptic flow at RHIC energies.

Viscosity effects in the QGP phase become significant at higher energies.

Shear viscosity near the QCD transition strongly influences collective flow.

Abstract

We study the influence of a temperature-dependent shear viscosity over entropy density ratio $\eta/s$, different shear relaxation times $\tau_\pi$, as well as different initial conditions on the transverse momentum spectra of charged hadrons and identified particles. We investigate the azimuthal flow asymmetries as a function of both collision energy and centrality. The elliptic flow coefficient turns out to be dominated by the hadronic viscosity at RHIC energies. Only at higher collision energies the impact of the viscosity in the QGP phase is visible in the flow asymmetries. Nevertheless, the shear viscosity near the QCD transition region has the largest impact on the collective flow of the system. We also find that the centrality dependence of the elliptic flow is sensitive to the temperature dependence of $\eta/s$.