Multipomeron Cuts and Hard Processes on Nuclei

With nuclear targets comes a new scale into the pQCD description of hard processes - the saturation scale. In the saturation regime, the familiar linear k_\perp-factorization breaks down and must be replaced by a nonlinear k_\perp-factorization, which accounts for absorptive and multiple scattering corrections to the hard process. Predictions for partial cross sections corresponding to a fixed number of cut Pomerons (the topological cross sections) can be obtained in a surprisingly straightforward manner. We discuss some applications to deep inelastic scattering.