Scaling patterns of the suppression of $\pi^0$ yields in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV: links to the transport properties of the QGP

Abstract

Suppression measurements for neutral pions ($\pi^0$) are used to investigate the predicted path length ($L$) and transverse momentum ($p_T$) dependent jet quenching patterns of the hot QCD medium produced in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. The observed scaling patterns show the predicted trends for jet-medium interactions dominated by radiative energy loss. They also allow simple estimates of the transport coefficient $\hat{q}$ and the ratio of viscosity to entropy density $\eta/s$. These estimates indicate that the short mean free path ($\lambda$) in the QCD medium leading to hydrodynamic-like flow with a small value of $\eta/s$, is also responsible for the strong suppression observed.