Nuclear suppression of dileptons at forward rapidities

Data from E772 and E866 experiments on the Drell-Yan process exhibit a significant nuclear suppression at large Feynman x(F). We show that a corresponding kinematic region does not allow to interpret this as a manifestation of coherence or a Color Glass Condensate. We demonstrate, however, that this suppression can be treated alternatively as an effective energy loss proportional to initial energy. To eliminate suppression coming from the coherence, we perform predictions for nuclear effects also at large dilepton masses. Our calculations are in a good agreement with available data. Since the kinematic limit can be also approached in transverse momenta (PT), we present in the RHIC energy range corresponding predictions for expected large-(PT) suppression as well. Since a new experiment E906 planned at FNAL will provide us with more precise data soon, we present also predictions for expected large-x(F) nuclear suppression in this kinematic region.