Abstract submitted to the
         International Europhysics Conference on High Energy Physics
                  July 12 - 18, 2001, Budapest, Hungary
_________________________________________________________________________




        Measurement of proton-dissociative diffractive photoproduction 
              of vector mesons at large momentum transfer at HERA

                    
                               ZEUS Collaboration





                                    Abstract


    Photoproduction of vector mesons, gamma p -> V N, where N is a
    low-mass dissociated state, has been measured in e^+p interactions 
    with the ZEUS detector at HERA using an integrated luminosity of 
    24 pb^{-1}. The data were taken at a photon-proton center-of-mass 
    energy W ~ 100 GeV and extend up to -t = 12 GeV^2, where t is the 
    square of the four-momentum transferred to the vector meson. The 
    differential cross section, dsigma/dt, and the results of
    a decay-angle analysis as a function of t for rho^0, phi and J/psi
    production are compared to expectations from phenomenological
    models. The ratios 
    dsigma/dt (gamma p -> phi N)/dsigma/dt (gamma p -> rho^0 N) and
    dsigma/dt (gamma p -> J/psi N)/dsigma/dt (gamma p -> \rho^0 N)
    are presented as a function of t.