Pomeron physics in diffractive deep inelastic scattering at large

Abstract

I review recent progress in the perturbative QCD approach to pomeron physics in deep inelastic scattering (DIS) at large 1 x .(refs.1–4). I discuss the crucial role the color transparency plays in a diffractive DIS, and how it can be quantified in terms of the wave function (WF) of (partonic) hadronic fluctuations of photons and universal, flavour independent, q q pair interaction cross section. Different DIS processes probe this universal cross section at different sizes. The emerging WF formalism greatly simplifies the involved calculations. I present quantitative predictions for the nuclear shadowing and the diffraction dissociation (DD) rate in DIS, and the valence and sea quark distributions in a QCD Pomeron. I point out a dramatic difference of sea densities in a nucleon as probed by muons and neutrinos and flavour dependence of the pomeron couplings in DD and conclude that perturbative QCD pomeron does not factorize. I emphasize a numerical importance of shadowing in deuterium for tests of the Gottfried sum rule.