ΣΛ Conversion in ΛH and in other S-shell hypernuclei

The binding energy of the Λ-particle in the $\text{J =}\text{1}\text{2}\text{and}\text{3}\text{2}$ states of _Λ³H and the doublet and quartet Λ-d scattering lengths are calculated with a separable ΛN-ΣN potential matrix, fitted to experimental data in ΛN and ΣN channels. The dependence of the results on ΛΣ coupling is explained in terms of a perturbative treatment of ΛΣ coupling. This perturbative treatment is also applied in a qualitative discussion of the effects of ΛΣ conversion in the J = 0 and 1 states of _Λ⁴H-_Λ⁴He and in the $\text{J =}\text{1}\text{2}$ state of _Λ⁵He. The importance of three-body ΛNN forces caused by ΣΛ coupling is stressed.