Energy dependence of diffractive production at HERA

Intrigued by the unexpected recent results from HERA, that the ratio σdiff/σtot is only weakly dependent on energy, we have attempted to reproduce this result within the framework of perturbative QCD. To this end we generalize the Kovchegov-McLerran formula for the ratio using Glauber-Mueller approach for shadowing corrections and AGK cutting rules. We investigate several phenomenological approaches and also compare with the successful Golec-Biernat-Wuesthoff model. We have not managed to reproduce the data, and conclude that, apparently, there are soft nonperturbative contributions present at short distances which should be included