In ultrarelativistic heavy ion collisions the secondary parton distribution in momentum space can be described by the superposition of the proton-proton (pp) collisions following the Glauber-Gribov model. RHIC data on high-pT hadron production display strong suppression in wide rapidity region, indicating strong induced energy loss for both transversally and longitudinally traveling partons. We investigate this suppression in a perturbative QCD improved parton model and extract the opacity of the produced hot matter in AuAu and CuCu collisions at energies sqrt(s)=200 AGeV and 63 AGeV at different rapidity values. I will discuss the direction dependent suppression and the properties of the hot matter both: in central and peripheral collsions.