Mass differences between members of isotopic-spin multiplets of hadrons are calculated in the MIT bag model. All low-mass SU(4) multiplets of spin 0, 1/2, 1, and 3/2 particles are considered. Both Coulomb and magnetic contributions to mass differences are evaluated without the assumption of SU(6)-degenerate intermediate states. The mass difference between the "up" and the "down" quarks inside the bag is not (necessarily) taken to be a constant; we propose a parameterization for it that works well for its contribution to known hadron electromagnetic mass differences. Based on the parametrization we present a class of sum rules for charmed-particle electromagnetic mass differences.

• Received 29 November 1976

DOI:https://doi.org/10.1103/PhysRevD.15.1885