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Exclusive diffractive photoproduction of heavy vector mesons (V=phi, J/psiand Upsilon) at HERA is studied in a model employing a dipole Pomeron exchange(P) with an inelastic gamma-P-V vertex. The model is fitted to the data ondsigma/dt, B and elastic sigma for Q^2=0 and beyond the threshold region. Theelastic cross sections for both phi and J/psi photoproduction show a moderateincrease within the HERA energy region. The flattening of the slope B(s)(little or no shrinkage) for J/psi is not correlated with the slope of thePomeron trajectory. Estimates for Upsilon photoproduction at HERA are given.Comment: 21 pages, LaTeX, 4 PostScript figures, uses axodraw.st

Photoproduction of heavy vector mesons at HERA – a test field for diffraction