Has the QCD Critical Point been Signaled by Observations at RHIC ?

Abstract

The shear viscosity to entropy ratio ($\hat{I}\cdot /s$) is estimated for the hot and dense QCD matter created in Au+Au collisions at RHIC ($\sqrt{s_{NN}}=200$ GeV). A very low value is found $\hat{I}\cdot /s\sim 0.1$, which is close to the conjectured lower bound ($1/4\ddot{I}€$). It is argued that such a low value is indicative of thermodynamic trajectories for the decaying matter which lie close to the QCD critical end point.

4 pages, 3 figures. Revised version, accepted for publication in PRL