Diagnostics of hot dense matter produced in Relativistic Heavy Ion Collisions

We study, in a pQCD calculation augmented by nuclear effects, the jet energy loss needed to reproduce the measured π ⁰ spectra in Au+Au collisions at large p _T , measured by PHENIX at RHIC at $\sqrt s = 200$ AGeV. Averaged energy loss obtained in the GLV formalism is applied in our recent calculation based on NLO pQCD (including shadowing and multiscattering). The method of jet tomography is capable to measure the opacity of the produced hot dense matter at RHIC energy in heavy ion collisions.