Energy transfer effects in meson exchange currents

Abstract

We first briefly review the important role of meson‐exchange currents in electroweak nuclear processes. We then discuss selected strong, electromagnetic, and weak nuclear processes where large effects due to a significant q02 (energy transfer) term appear. Such terms can originate either in vertex couplings or propagators which in general depend on qu2, the square of the four momentum transfer. Because one is often using a non‐relativistic reaction formalism there can be considerable ambiguity associated with keeping energy transfer terms. Nevertheless, such effects must be clarified because the class of reactions where the q0≠0 contribution is potentially crucial involves such important studies as high‐energy deuteron photo disintegration and proton induced nuclear pion production. Several examples using non‐relativistic nucleons are presented and discussed. It is suggested that use of Dirac Phenomenology may be a tractable method for considering reactions involving large energy transfer and thus avoiding the difficulties associated with a non‐relativistic reduction.