HARD DIFFRACTION AT HERA IN THE DIPOLE MODEL OF BFKL DYNAMICS

Using the QCD dipole picture of the hard BFKL pomeron, we derive the g eneral expressions of the elastic and inelastic components of the prot on diffractive structure functions. We obtain a good seven-parameter f it (including a secondary reggeon contribution) to data taken at HERA by the H1 and ZEUS Collaborations. The main characteristic features of the model in reproducing the data are discussed, namely the effective pomeron intercept, the scaling violations and the beta-dependence. A difference obtained in the separate H1 and ZEUS fits leads us to analy ze directly the differences between both measurements. Predictions on R, the ratio of longitudinal to transverse photon cross sections are p erformed and lead to very large values at high beta and large virtuali ty Q which may lead to a discrimination between models. (C) 1998 Elsev ier Science B.V.