The generalised vector dominance/colour-dipole picture of deep-inelastic scattering at low x

We give a detailed account of the recently formulated generalised vector do minance/colour-dipole picture (GVD/CDP) of deep-inelastic scattering at low x congruent to Q(2)/W-2, including photoproduction. The approach, based on gamma*(q (q) over bar) transitions, q (q) over bar propagation and diffrac tive (q (q) over bar) p scattering via the generic structure of the two-glu on exchange, provides a unique and quantitatively successful theory for the gamma *p total cross section, sigma (gamma *p)(W-2, Q(2)), at low x. The G VD/CDP is shown to imply the empirical low-x scaling law, sigma (gamma *p)( W-2,Q(2)) = sigma (gamma *p)(eta) with eta = (Q(2) + m(o)(2))/Lambda (2)(W- 2), that was established by a model-independent analysis of the experimenta l data.