SU(3)-symmetry breaking and configuration mixing in baryon semileptonic decays.

Abstract

We discuss small contributions to baryon semileptonic decays which provide corrections to the simplest SU(3)-symmetric formulas. In particular, we consider (1) SU(3)-symmetry breaking resulting from the wave-function deformations due to the $s\ensuremath{-}u$, $d$ quark mass difference and (2) the effects of the configuration mixing of $^{2}S_{M}$ and $^{2}S_{S}$ states, originating from QCD hyperfine interactions. Both effects are treated in combination with the form-factor suppression effect which is operative if the three-momentum transfer between the initial and final hadron is nonzero. Our estimates are performed in the framework of the harmonic-oscillator quark model. While the inclusion of the $s\ensuremath{-}u$, $d$ quark mass difference leads to an unacceptable $\frac{{g}_{A}}{{g}_{V}}$ ratio for $\ensuremath{\Lambda}\ensuremath{\rightarrow}p{e}^{\ensuremath{-}}\ensuremath{\nu}$ semileptonic decay, the corrections due to configuration mixing do not lead to disagreement with the data. Better measurements of the $\ensuremath{\Xi}\ensuremath{\rightarrow}n{e}^{\ensuremath{-}}\ensuremath{\nu}$ and $\ensuremath{\Xi}\ensuremath{\rightarrow}\ensuremath{\Lambda}{e}^{\ensuremath{-}}\ensuremath{\nu}$ decays are needed if a choice is to be made between the standard SU(3)-symmetric parametrization and the pattern of SU(3) breaking resulting from configuration mixing.