Hypernucleus _Λ⁴⁰Ca and recent hyperon-nucleon potentials

The Nijmegen NSC89 and the most recent NSC97 hyperon-nucleon potentials are adopted to study the structures of hypernuclei. Investigations are concentrated on the hypernucleus _Λ⁴⁰Ca by using our two-frequency shell-model folded-diagram approach. We first calculate the YN G matrix with an exact Pauli exclusion operator. The nucleon frequency for the harmonic oscillator basis wave function is chosen from the empirical formula ħω_N=45A^-1/3-25A^-2/3, while the hyperon one is obtained as the frequency when the lowest hyperon single-particle energy in the hypernucleus reaches a saturation minimum. The energy-independent effective interaction V_eff is then obtained from the YN G matrix elements, using a Q̂-box folded-diagram framework. We will examine how our calculated spectra vary via these different versions of the realistic hyperon-nucleon potentials. Special attention is drawn on the contribution of the ΛN-ΣN coupling diagram. Although this diagram contributes significantly to V_eff in most cases, it does not alter much to the final spectrum.