Diffraction at Hera, Color Opacity and Nuclear Shadowing in Dis off Nuclei

The QCD factorization theorem for diffractive processes in DIS is used to derive the leading twist contribution to the nuclear shadowing of partons due to the coherent projectile (photon) interactions with two nucleons (the low thickness limit). We calculate nuclear structure functions in the limit of large thickness (the black interaction limit). Based on the current analyzes of diffraction at HERA we find that the average strength of the interactions which govern diffraction in the gluon sector at x ≤ 10 −3 , Q 0 = 2GeV is ∼ 50mb. This is three times larger than in the quark sector and suggests a later onset of the Bjorken scaling in the gluon sector. We use this diffractive information to estimate the higher order shadowing terms due to the photon interactions with N ≥ 3 nucleons which are important for the scattering of heavy nuclei and to calculate nuclear shadowing and Q 2