Pion Electroproduction,ρProduction by Pions, and Vector-Meson Dominance

A unified account for the isovector contribution to $\rho$ production, pion photoproduction, and electroproduction in the near-forward direction of the pion is given, and its relationship to vector-meson dominance is discussed. The high-energy limit is discussed in detail, first for the electric Born model, and then for a more realistic model derived from fixed-$t$ dispersion relations. Very simple features emerge, which in most cases can also be observed at low energies. Numerical results of our model are given for all three types of reactions.