Λ−ΣConversion andΛnpIsospin-Zero Bound States

The Faddeev equations with nonlocal separable Yamaguchi potentials have been used to calculate the binding energy $B_{\Lambda }$ of the $\Lambda$ hyperon in the spin-doublet and spin-quartet $\Lambda \mathrm{np}$ isospin-zero systems. The calculations have been performed with explicit consideration of $\Lambda -\Sigma$ virtual conversion in neither, one, and both of the hyperon-nucleon ($\mathrm{YN}$) spin channels. Relative to the case when it is neglected, $\Lambda -\Sigma$ conversion changes the $\Lambda Nt$ matrix and introduces a $\Lambda \mathrm{NN}$ force. Results have been obtained when only the change in the $\Lambda Nt$ matrix was considered, as well as when both this change and the $\Lambda \mathrm{NN}$ force were used. The effect of the change in the $\Lambda Nt$ matrix is always to reduce $B_{\Lambda }$. The effect of the $\Lambda \mathrm{NN}$ force depends upon the $\mathrm{YN}$ spin channel in which it is used as well as the total spin of the $\Lambda \mathrm{np}$ system.