VECTOR-MESON DOMINANCE AND DIFFRACTIVE ELECTROPRODUCTION OF VECTOR MESONS

A vector-meson dominance model of diffractive electroproduction of vector mesons at high energies is presented. The assumption that the invariant amplitudes are slowly varying as a function of the vector-meson mass, when extrapolating to the spacelike region, is shown to lead to serious difficulties when combined with helicity independence, i.e. equality of transverse and longitudinal on-mass-shell vector-meson forward-scattering helicity amplitudes at high energies. The assumption is adopted, therefore, that the helicity amplitudes are slowly varying, apart from the factors which guarantee the vanishing of the longitudinal amplitudes in the limit of zero mass. Assuming, in addition, helicity non-flip and helicity independence for vector-meson scattering, we derive expressions for the cross section for electroproduction of vector mesons and for the vector-meson spin-density matrix elements. We also present our conclusions on the total electroproduction cross section. © 1969.