Elastic and proton-dissociative photoproduction of J/ψ mesons at HERA

Cross sections for elastic and proton-dissociative photoproduction of J / mesons are measured with the H1 detector in positron-proton collisions at HERA. The data were collected at ep centre-of-mass energies s 318 GeV and s 225 GeV, corresponding to integrated luminosities of L = 130 pb -1 and L = 10.8 pb -1 , respectively. The cross sections are measured as a function of the photon-proton centre-of-mass energy in the range 25 < W p < 110 GeV. Differential cross sections d/dt, where t is the squared four-momentum transfer at the proton vertex, are measured in the range |t| < 1.2 GeV 2 for the elastic process and |t| < 8 GeV 2 for proton dissociation. The results are compared to other measurements.