Elliptic Flow at Finite Shear Viscosity in a Kinetic Approach at RHIC

TL;DR

This paper investigates how finite shear viscosity and freeze-out dynamics influence elliptic flow at RHIC using a covariant parton cascade, highlighting the importance of viscosity in understanding QGP properties.

Contribution

It demonstrates that shear viscosity effects are crucial for interpreting elliptic flow data and supports the nearly perfect fluid nature of QGP through kinetic modeling.

Findings

Finite shear viscosity significantly affects elliptic flow.

Elliptic flow data is consistent with a shear viscosity to entropy ratio of 0.1-0.2.

Results support the nearly perfect fluid behavior of QGP.

Abstract

Within a covariant parton cascade, we discuss the impact of both finite shear viscosity $\eta$ and freeze-out dynamics on the elliptic flow generated at RHIC. We find that the enhancement of $\eta/s$ in the cross-over region of the QGP phase transition cannot be neglected in order to extract the information from the QGP phase. We also point out that the elliptic flow $v_2(p_T)$ for a fluid at $\eta/s \sim 0.1-0.2$ is consistent with the one needed by quark number scaling drawing a nice consistency between the nearly perfect fluid property of QGP and the coalescence process.