Gauge Fields, Sources, and Electromagnetic Masses

The hypothesis of strong-interaction gauge fields, with non-Abelian gauge invariance broken only by the $1^{-}$ particle mass terms, gives a natural source theory setting for the introduction of electromagnetic effects. The electromagnetic potential vector appears as a compensating field in the mass terms of the neutral $1^{-}$ particles. The resulting electromagnetic self-action is used to discuss mass displacements. The pion electro-magnetic mass is computed in a number of ways—by direct calculation of various processes and by chiral methods, in two variants. The relationship of these approaches is established. A phenomenological modification of the chiral evaluation gives perfect agreement with the observed value. It is found, however, that the ${\left(\frac{m_{\pi }}{m_{\rho }}\right)}^2$ terms, which are neglected in this method, are not very small. Baryon electromagnetic mass splittings are described by a simple adaptation of gross mass-spectrum empirics. Agreement with the data is excellent.