Hard Diffraction From Quasi - Elastic Dipole Scattering

The contribution to diffraction dissociation of virtual photons due to quasi-elastic scattering of the q-¯ q component is calculated in the framework of the QCD dipole picture. Both longitudinal and transverse components of the cross-section are given. It is shown that, at fixed mass of the diffractively produced system, quantum mechanical interference plays an important rôle. Phenomenological consequences are discussed. 1. Recently, new measurements of the proton diffractive structure function at small x and large Q 2 were presented by H1 and ZEUS experiments