Two-Field Couplings with Especial Reference to Photon-Neutral Meson Interaction

Abstract

The coupling of two particles of identical quantum numbers, apart from their mass, is considered. It is shown that the effects of direct transitions of one particle into another can be treated exactly in terms of six parameters. These can be taken to be the true masses, the mixing parameters, and the partially renormalized coupling constants. This is a generalization of conventional mass renormalization for a single field. The special case of a photon and a neutral vector meson is discussed. Resonance effects may occur if the photon is virtual. However, gauge invariance and the vanishing of the photon mass forbid such effects for real photons, unless a dynamical accident relates the bare photon mass to the effective photon-meson couplings in a particular way.