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: $^{\phantom{6}6}_{ΛΛ}$He, $^{10}_{ΛΛ}$Be and $^{13}_{ΛΛ}$B. 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 $^1 S_0$ $ΛΛ$ bound states provided the $ΛΛ-ΞN$ coupling can be neglected.

49 pages, LaTeX + 8 ps-figure files