Vector meson dominance predictions for single pion electroproduction

Abstract

Predictions for π + electroproduction are obtained by using vector meson dominance to continue the pion photoproduction amplitudes to spacelike values of the virtual photon mass. The continuation is performed by formulating vector dominance in terms of invariant rather than helicity amplitudes, and the longitudinal polarization states of the virtual photon are given in terms of the photoproduction invariant amplitudes. Previous vector dominance predictions for electroproduction from vector meson production have encountered difficulty with the sign of the longitudinal-transverse interference term in the cross section. In the present model, however, the structure of this term is explained naturally in terms of the kinematical k 2 dependence of the longitudinal amplitudes, and excellent agreement with all the data is obtained. These results complete the unified description of vector meson production, pion photoproduction, and pion electroproduction in terms of a covariant vector meson dominance model.