Photoproduction off nuclei and pointlike photon interactions. I. Cross sections and nuclear shadowing

High energy photoproduction off nuclear targets is studied within the Glauber-Gribov approximation. The photon is assumed to interact as a $q\mathrm{q¯}$ system according to the generalized vector dominance model and as a “bare photon” in direct scattering processes with target nucleons. We calculate total cross sections for interactions of photons with nuclei taking into account coherence length effects and pointlike interactions of the photon. Results are compared to data on photon-nucleus cross sections, nuclear shadowing, and quasielastic $\rho$ production. Extrapolations of cross sections and of the shadowing behavior to high energies are given.