Four-Body Calculation of 4Λ H and 4Λ He with Realistic yn and NN Interactions

We carried out four-body calculations of ⁴_Λ H and ⁴_Λ He taking both the 3N + Λ and 3N + Σ channels explicitly with the use of realistic NN and YN interactions. The Σ-channel component plays an important role in binding energies of the A = 4 hypernuclei though the adimixture is approximately 1 %. The ΛN - ΣN coupling is found to be of central-force type in the Nijmegen model D and of tensor-force type in the model D.