Departures from the Eightfold Way. II. Baryon Electromagnetic Masses

Abstract

The leading nontadpole contributions to the electromagnetic mass splittings of the baryons are calculated. Best fits to experiment are used for the nucleon form factors; the strange baryon form factors are obtained from these by unitary symmetry. Account is taken of the breakdown of unitary symmetry by using experimental masses in intermediate states and by including the effects of $\theta -\omega$ mixing. These calculations and the assumption of tadpole dominance are used to fit the six mass splittings of baryons and pseudoscalar mesons with one free parameter. All of the splittings are in good agreement with experiment except for the kaon splitting, which has the right sign but only $\frac{2}{3}$ of the proper magnitude. The results of a preliminary version of this calculation were reported in the first paper in this series.