Factorization breaking in diffractive photoproduction of dijets-a review

I compare the latest H1 and ZEUS data on diffractive dijet photoproduction with next-to-leading order QCD predictions in order to see whether a rapidity gap survival probability of less than one is supported by the data. I find evidence for this hypothesis when assuming global factorization breaking for both the direct and resolved photon contributions, in which case the suppression factor would have to be strongly -dependent, and when assuming factorization breaking for the resolved or in addition the related direct initial-state singular contribution only, where it would be independent of .