Nearly perfect fluid in Au+Au collisions at RHIC

TL;DR

This paper analyzes RHIC Au+Au collision data using dissipative hydrodynamics to estimate the quark-gluon plasma's viscosity, finding it to be very close to a perfect fluid with minimal viscosity.

Contribution

It provides a phenomenological estimate of QGP viscosity using a simultaneous fit to multiple observables within Israel-Stewart hydrodynamics.

Findings

Estimated η/s = 0.07 ± 0.03 ± 0.14

QGP behaves nearly as a perfect fluid

Quantified uncertainties in viscosity measurement

Abstract

In the Israel-Stewart's theory of dissipative hydrodynamics, we have analysed the STAR data on $\phi$ meson production in Au+Au collisions at $\sqrt{s}$=200 GeV. From a simultaneous fit to $\phi$ mesons multiplicity, mean $p_T$ and integrated $v_2$, we obtain a phenomenological estimate of QGP viscosity, $\eta/s =0.07 \pm 0.03 \pm 0.14$, the first error is due to the experimental uncertainty in STAR measurements, the second reflects the uncertainties in initial and final conditions of the fluid.