Hard scattering factorization and light cone Hamiltonian approach to diffractive processes

We describe diffractive deep inelastic scattering in terms of diffractive parton distributions. We investigate these distributions in a Hamiltonian formulation that emphasizes the space-time picture of diffraction scattering. For hadronic systems with small transverse size, diffraction occurs predominantly at short distances and the diffractive parton distributions can be studied by perturbative methods. For realistic, large-size systems we discuss the possibility that diffractive parton distributions are controlled essentially by semihard physics at a scale of non-perturbative origin of the order of a GeV. We find that this possibility accounts for two important qualitative aspects of the diffractive data from HERA: the flat behavior in β and the delay in the fall-off with Q2