saturated virtual nuclear CGC fields[@McLerran:2004fg; @Eskola:2002qz]. This scale controls the formation time $\hbar/p_0\approx 0.2$ fm/c of the initially out-of-equilibrium (mostly gluonic) QGP. The success of the hydrodynamics requires that local equilibrium be achieved on a fast proper time scale $\tau_{eq}\approx (1-3)/p_0 < 0.6$ fm/c. The temperature at that time is $T(\tau_{eq})\approx (\epsilon_0/(1-3)\times 12)^{1/4} \approx 2 T_c$.

In HIJING model[@ToporPop:2002gf], the mini-jet cutoff is $p_0=2-2.2$ GeV limits the number of mini-jets well below 1000. The inferred opacity of the QGP is much higher and consistent with the CGC and EKRT estimates.

 and Single Jet Tomography
--------------------------

In order to illustrate the ideas behind jet tomography, I will simplify the discussion here to a schematic form. See [@Gyulassy:2003mc] for details. The fractional radiative energy loss of a high energy parton in an expanding QGP is proportional to the position weighed line integral over color charge density $\rho(\vec{x}_\perp,\tau)$ $$\Delta E_{GLV}/E \approx  C_2 \kappa(E)  \int_{0}^{L(\phi)} d\tau\; 
\tau\rho(\vec{x}_\perp(\tau),\tau)\;\;,
\label{dee1}$$ where $C_2$ is the color Casimir of the jet parton and $\kappa(E)$ is a slowly varying function of the jet energy [@Gyulassy:2003mc]. The azimuthal angle sensitive escape time, $L(\phi)$, depends on the initial production point and direction of propagation relative to the elliptic flow axis of 