The proton-dissociative diffractive photoproduction of J/psi mesons has been studied in ep collisions with the ZEUS detector at HERA using an integrated luminosity of 112 pb. The cross section is presented as a function of the photon-proton centre-of-mass energy and of the squared four-momentum transfer at the proton vertex. The results are compared to perturbative QCD calculations. The double differential inelastic J/psi photoproduction cross section as function of the squared transverse momentum of the J/psi in bins of the inelasticity z has been measured. An integrated luminosity of 468 pb-1 was used corresponding to the full data sample collected by the ZEUS experiment. The events were required to have 0.1 < z < 0.9, pt > 1 GeV and 60 < W < 240 GeV, where pt is the transverse momentum of the J/psi and W is the photon-proton centre-of-mass energy. The J/psi mesons were identified through their decay into muon pairs. The double differential cross section measurements are compared to the most recent theoretical predictions.
Dr Aharon LEVY (Tel Aviv University)