We report the study of the nuclear modification factor R_{AuAu} as function of pT and pseudo-rapidity in Au+Au collisions at top RHIC energy. We find this quantity almost independent of pseudo-rapidity. We use the pbar/pi- ratio as a probe of the parton density and the degree of thermalization of the medium formed by the collision. The pbar/pi- ratio has a clear rapidity dependence. The combination of these two measurements suggests that the pseudo-rapidity dependence of the R_{AuAu results from the competing effects of energy loss in a dense and opaque medium and the modifications of the wave function of the high energy beams in the initial state.
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