PARTONIC PICTURE OF NUCLEAR SHADOWING AT SMALL-X

We investigate the nuclear shadowing mechanism in the context of pertu rbative QCD and the Glauber-Gribov multiple scattering model. Using re cent HERA data on nucleon structure function at small x, we put string ent constrains on the nucleon gluon density in the double-logarithm ap proximation. We suggest that the scaling violation of the nucleon stru cture function in the region of small-x and semihard scale Q(2) can be reliably described by perturbative QCD which is a central key to the understanding of the scale dependence of the nuclear shadowing effect. Our results indicate that while the shadowing of the quark density ar ises from an interplay between ''soft'' and semihard QCD processes, wh ile gluon shadowing is largely driven by a perturbative shadowing mech anism. We demonstrate that the gluon shadowing is a robust phenomenon at large Q(2) and can be unambiguously predicted by perturbative QCD. (C) 1998 Elsevier Science B.V.