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

摘要

The shear viscosity to entropy ratio ($\eta/s$) is estimated for the hot anddense QCD matter created in Au+Au collisions at RHIC ($\sqrt{s_{NN}}=200$ GeV).A very low value is found $\eta/s \sim 0.1$, which is close to the conjecturedlower bound ($1/4\pi$). It is argued that such a low value is indicative ofthermodynamic trajectories for the decaying matter which lie close to the QCDcritical end point.