Factorisation in diffraction

Recent experimental data on dijet cross sections in diffractive photoproduction at HERA collider were analysed with emphasis on QCD factorisation breaking effects. Dijet photoproduction data of jets with low transverse energy indicated a possible dependence on ET of the suppression of jet production with respect to the NLO QCD predictions. However, this suppression exhibited no significant dependence on the fraction xγ of the photon four-momentum entering the hard process. The ratio of diffractive to inclusive cross section for dijets in photoproduction was also measured for the first time.