Abstract submitted to the 
        International Europhysics Conference on High Energy Physics
                 July 12 - 18, 2001, Budapest, Hungary
    
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        Proton-dissociative photoproduction of vector mesons at 
        large momentum transfer with a leading nucleon at HERA

                    
                            ZEUS Collaboration



                                 Abstract


    Photoproduction of vector mesons, V, at large momentum transfer
    (|t| > 1 GeV^2) has been observed for the reaction gamma p -> V N, 
    where N is a low-mass dissociated state, with the ZEUS detector 
    at HERA using an integrated luminosity of 24 pb^{-1}. A leading 
    proton or neutron with low squared transverse momentum 
    (p_T^2 <~ 0.5 GeV^2) and carrying a large fraction of the initial-
    state proton's energy (x_L >~ 0.2) is observed in the final state. 
    The rate of leading-proton (-neutron) production for high-|t| 
    vector mesons is compared to the rate in deep inelastic scattering. 
    The x_L distributions are also compared.