Аннотация
The photoproduction of isolated photons has been measured in diffractive events recorded by the ZEUS detector at HERA. Cross sections are evaluated in the photon transverse-energy and pseudorapidity ranges $5<{E}_{T}^{\ensuremath{\gamma}}<15\text{ }\text{ }\mathrm{GeV}$ and $\ensuremath{-}0.7<{\ensuremath{\eta}}^{\ensuremath{\gamma}}<0.9$, inclusively, and also with a jet with transverse energy and pseudorapidity in the ranges $4<{E}_{T}^{\text{jet}}<35\text{ }\text{ }\mathrm{GeV}$ and $\ensuremath{-}1.5<{\ensuremath{\eta}}^{\text{jet}}<1.8$, using a total integrated electron-proton luminosity of $456\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$. A number of kinematic variables were studied and compared to predictions from the rapgap Monte Carlo model. An excess of data is observed above the rapgap predictions for ${z}_{\mathbb{P}}^{\mathrm{meas}}>0.9$, where ${z}_{\mathbb{P}}^{\mathrm{meas}}$ is the fraction of the longitudinal momentum of the colorless ``Pomeron'' exchange that is transferred to the photon-jet final state, giving evidence for direct Pomeron interactions.