Λ-Σ conversion in Λ4He and Λ4H based on a four-body calculation

Abstract

Precise four-body calculations for ${}_{\ensuremath{\Lambda}}^{4}\mathrm{He}$ and ${}_{\ensuremath{\Lambda}}^{4}\mathrm{H}$ have been performed in the framework of a variational method employing Jacobi-coordinate Gaussian-basis functions. All of the $\mathrm{NNN}\ensuremath{\Lambda}$ and $\mathrm{NNN}\ensuremath{\Sigma}$ rearrangements are explicitly taken into account for the first time in the context of realistic $\mathrm{NN}$ and $\mathrm{YN}$ interactions. The role of $\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Sigma}$ conversion and the size of the virtual $\ensuremath{\Sigma}$ component in ${}_{\ensuremath{\Lambda}}^{4}\mathrm{He}$ and ${}_{\ensuremath{\Lambda}}^{4}\mathrm{H}$ are discussed.