The "Perfect" Fluid Quenches Jets Almost Perfectly

TL;DR

This paper discusses how the quark-gluon plasma produced in heavy ion collisions at RHIC exhibits near-perfect fluidity with low shear viscosity and strongly suppresses energetic hadron emission, indicating strong coupling yet quasi-particle behavior.

Contribution

It links jet quenching phenomena with the fluid properties of the quark-gluon plasma, suggesting a strongly coupled but quasi-particle describable medium.

Findings

Low shear viscosity close to the unitarity bound

Strong suppression of energetic hadrons

Indications of strong coupling with quasi-particle features

Abstract

The QCD matter produced in nuclear collisions at the Relativistic Heavy Ion Collider (RHIC) has been found to have a very low shear viscosity, which is close to the lower bound allowed by unitarity. The matter has also been found to strongly suppress the emission of energetic hadrons. This phenomenon, called "jet quenching" is interpreted to be the result of a large energy loss by the precursor parton on its path through the dense matter, primarily due to gluon radiation. I discuss how the two phenomena are related. The RHIC data suggest, in some scenarios of jet quenching, that the quark-gluon plasma created in nuclear collisions is characterized by strong coupling, but still admits a quasi-particle description.