Pseudorapidity dependence of parton energy loss in relativistic heavy ion collisions

We analyze the recent data from the BRAHMS Collaboration on the pseudorapidity dependence of nuclear modification factors in Au +Au collisions at √s NN =200 GeV by using the full three dimensional hydrodynamic simulations for the density effects on parton energy loss. We first compute the transverse spectra at η=0 and 2.2, and next take a ratio R η =R AA (η=2.2)/R AA (η=0) , where R AA is a nuclear modification factor. It is shown that hydrodynamic components account for R η ≅1 at low p T and that quenched perturbative QCD components lead to R η <1 at high p T which are consistent with the data. Strong suppression at η=2.2 is compatible with the parton energy loss in the final state