The flavor-spin symmetries of heavy quark effective theory imply that in the infinite heavy quark mass limit the magnetic moments, radiative decay rates, single pion emission decay rates, and the $\Sigma$ $\Delta I=2\mathrm{}$ isospin mass splittings for the heavy $\Sigma$ baryon systems approach finite but undetermined values, independent of the spin of the $\Sigma$ baryon and the flavor of the heavy quark. We propose, with supporting evidence, that the flavor-spin symmetries for those processes, with the isoscalar quark as a spectator, can be extended to all isoscalar quarks and thus overlap with the low-energy SU(6) symmetry through the strange quark. By interpolating between the flavor-spin symmetries at the heavy quark masses and the strange quark mass we determine these interesting properties of the heavy $\Sigma$ baryons from the available low-energy data. We also discuss the interesting pattern of theoretical calculations and the experimental conflict on the ${\Sigma }_c$ $\Delta I=2\mathrm{}$ isospin mass splitting.

• Received 28 May 1996

DOI:https://doi.org/10.1103/PhysRevD.54.6890