Abstract submitted to the
         XXXth International Conference on High Energy Physics
                July 27 - August 2, 2000, Osaka, Japan
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       Measurement of diffractive photoproduction of vector mesons at
                  large momentum transfer at HERA


                               ZEUS Collaboration





                                    Abstract


Elastic and proton-dissociative photoproduction of rho^0, phi and
J/psi mesons have been measured in e^+p interactions up to -t=3 GeV^2,
where t is the four-momentum-transfer squared at the photon--vector
meson vertex, in the ZEUS detector at HERA. The average gamma-proton
centre-of-mass energy <W> = 94 GeV.  The differential cross sections,
dsigma/dt, for rho, phi and J/Psi mesons and the spin-density matrix
elements for the rho have been measured.  The Pomeron trajectory has
been derived from the W dependence of the elastic differential
cross-section dsigma/dt for both rho and phi mesons.