Partonic picture of nuclear shadowing at small x

We investigate the nuclear shadowing mechanism in the context of perturbative QCD and the Glauber-Gribov multiple scattering model. Using recent HERA data on nucleon structure function at small x, we put stringent constrains on the nucleon gluon density in the double-logarithm approximation. We suggest that the scaling violation of the nucleon structure function in the region of small-x and semihard scale Q² 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 arises from an interplay between "soft" and semihard QCD processes, while gluon shadowing is largely driven by a perturbative shadowing mechanism. We demonstrate that the gluon shadowing is a robust phenomenon at large Q² and can be unambiguously predicted by perturbative QCD.