PUB - Publikationen an der Universität Bielefeld

The empirical scaling law, wherein the total photo-absorption cross section depends on the single variable eta = (Q(2) + m(0)(2))/A(2)(W-2), provides em pirical evidence for saturation in the sense of sigma(gamma*p)(W-2, Q(2))/sigma(gammap)(W-2) --> 1 for W-2 --> infinity at fixed Q(2). The total photo-absorption cross section is related to elastic diffraction in terms of a sum rule. The excess of diffractive production over the elastic component is due to inelastic diffraction that contains the production of hadronic states of higher spins. Motivated by the diffractive mass spectrum, the Generalized Vector Dominance/Color Dipole Picture (GVD/CDP) is extended to successfully describe the DIS data in the full region of x < 0. 1, all Q(2) > 0, where the diffractive two-gluon exchange mechanism dominates.