PUB - Publikationen an der Universität Bielefeld

Including destructively interfering off-diagonal transitions of diffraction-dissociation type, we arl ive at a formulation of GVD for exclusive vector-meson production in terms of a continuous spectral representation of dipole form. The transverse cross-section, sigma(T.gamma*p) (-->) (Vp), behaves asymptotically as 1/Q(4), while R-v equivalent to sigma(L.gamma*p --> Vp)/sigma(T.gamma*p --> Vp) becomes asymptotically constant. Contributions violating s-channel helicity conservation stay at the level established in low-energy photoproduction and diffractive hadron-hadron interactions. The data on rho(0)-meson production from the Fermilab E665 Collaboration and on phi- and rho(0)-meson production from HERA are found to be in agreement with these predictions. (C) 1999 Elsevier Science B.V. All rights reserved.