High-| t| Diffraction and Deeply Virtual Compton Scattering

Abstract

At the HERA ep collider the diffractive productions of J / ψ mesons and photons were measured. The differential J / ψ cross section is studied in the range 2 | t | 30 GeV 2 , where | t | is the square of the 4-momentum transferred at the proton vertex. The production of photons in the process γ ∗ p → γ Y , where Y denotes the proton dissociative system or the elastically scattered proton, is measured in two different kinematical regimes: i) in photoproduction at large transverse momentum p t γ > 2 GeV and ii) in electroproduction at 4 Q 2 80 GeV 2 . The measurements are compared with perturbative QCD models based on BFKL and DGLAP evolution and with Colour Dipole models.