Parton Distributions in Nuclei at Small x

We study the nuclear shadowing effect in the context of Glauber-Gribov multiple-scattering model and perturbative QCD. We find that at small x, the $Q^2$ evolution of the shadowing is much slower than the DGLAP evolution, due to the multiple scatterings at small x. We show that the gluon shadowing at small x and for $Q^2 > 3GeV^2$ is perturbative in nature and does not depend on the initial, non-perturbative condition. We evaluate the impact parameter dependence of the gluon distribution and show that it is a non-linear effect in the nuclear thickness function.