The Nuclear Modification Factor at Large Rapidities

RHIC data on high- p T hadron production display strong suppression in a wide rapidity region, indicating strong induced energy loss for both transversally and longitudinally traveling partons. We investigate the interplay of energy loss and rapidity dependence in a perturbative QCD improved parton model, and estimate the opacity of the produced hot matter in AuAu collisions at energies s = 200 A GeV and 63 A GeV at different rapidity values. Direction-dependent suppression offers the possibility to study the geometry of the hot matter.