Double-Λ hypernuclei and the nuclear medium effective ΛΛ interaction

Abstract

We fit the 1 S 0 ΛΛ interaction in the nuclear medium to the masses of the experimentally known double-Λ hypernuclei: ΛΛ 6He, ΛΛ 10Be and ΛΛ 13B. We derive this effective interaction from OBE Jülich ΛΛ-type potentials and using both Hartree-Fock and variational approaches. We find that the inclusion of ΛΛ correlations in the variational scheme leads to significant differences and a better understanding of the dynamical features of the system. We investigate the sensitivity of the binding energies and the mesonic decay widths of the above double-Λ hypernuclei to the ωΛΛ coupling and the form factor at the σΛΛ vertex. We also use this effective interaction to predict binding energies and pionic decay widths of heavier double-Λ hypernuclei, not discovered yet. Finally, we discard the existence of 1S 0 ΛΛ bound states provided the ΛΛ-Ξ N coupling can be neglected.