Abstract
The precise four-body calculations for ^4_ΛHe and ^4_ΛH have been performed in the frame-work of the variational method with Jacobian-coordinate Gaussian-basis functions. All the rearrangement channel of both NNNA and NNNΣ are explicitly taken into account for the first time with the use of realistic NN and YN interactions. The role of Λ-Σ conversion and the amount of the virtual Σ-component in ^4_ΛHe and ^4_ΛH are discussed.
