Exlusive diffraction at HERA

AbstractThe cross section of the diffractive process γπ+→ρ0π+ was measured first time in ep scattering. Elastic and proton-dissociative photoproduction of J/Ψ were measured as a function of the four-momentum transfer squared and of the photon-proton centre-of-mass energy. The energy dependence is consistent with a model prediction assuming a two-gluon exchange. The ratio of cross sections of the elastic production of Ψ(2S) and J/Ψ was measured with inproved precision in Deep Inelastic Scattering (DIS). The diffractive exchange was studied in a measurement of exclusive dijet production in DIS. The data are consistent with a model prediction assuming a two-gluon exchange