Exclusive photoproduction of J/ψ mesons at HERA

The exclusive photoproduction of J/ψ mesons, γp→J/ψp, has been studied in ep collisions with the ZEUS and H1 detectors at HERA using the e+e− and μ+μ− decay modes. The total cross section has been measured as a function of the photon-proton center-of-mass energy, W, in the kinematic range 20⩽W⩽290 GeV for ZEUS and 26⩽W⩽285 GeV for H1. The differential cross section dσ/dt, where t is the squared four-momentum at the proton vertex, has been measured. The Pomeron trajectory has been determined.