Violations of SU(6) Selection Rules from Quark Hyperfine Interactions

Abstract

The decay amplitudes for ${D}_{15}\ensuremath{\rightarrow}p\ensuremath{\gamma}$, the amplitude for ${D}_{05}\ensuremath{\rightarrow}\overline{K}N$, and the charge radius of the neutron are zero in the SU(6) limit, but are observed to be nonzero. We show that all of these SU(6)-violating effects can be understood quantitatively in terms of the admixtures of excited-state configurations in the nucleon expected on the basis of color hyperfine interactions. In particular, the admixture of $^{2}S_{M}$ (i.e., [70, ${0}^{+}$]) with an amplitude of about - \textonequarter{} is central to understanding all three effects.