We demonstrate that the main part of the observed nuclear suppression of dilepton and charmonium production, especially the x dependence of the suppression, can be explained by the absorption of fast initial partons. We describe several reactions at different energies using one empirical form of the parton absorption cross section. The factorization theorem constraints and some alternative models are discussed. The obtained description of data suggests that the parton recombination and the excess pion contribution are unimportant in nuclei. A gluon excess in nuclei at x∼0.1 is compatible with the present model. © 1996 The American Physical Society.

• Received 26 April 1995

DOI:https://doi.org/10.1103/PhysRevC.53.2401