Double-Lambda hypernuclei and the nuclear medium effective Lambda Lambda interaction

We fit the S-1(0) Lambda Lambda interaction in the nuclear medium to the ma sses of the experimentally known double-Lambda hypernuclei: He-6(Lambda Lam bda), Be-10(Lambda Lambda) and B-13(Lambda Lambda). We derive this effectiv e interaction from OBE Julich Lambda Lambda-type potentials and using both Hartree-Fock and variational approaches. We find that the inclusion of nn c orrelations in the variational scheme leads to significant differences and a better understanding of the dynamical features of the system. We investig ate the sensitivity of the binding energies and the mesonic decay widths of the above double-Lambda hypernuclei to the omega Lambda Lambda coupling an d the form factor at the sigma Lambda Lambda vortex, We also use this effec tive interaction to predict binding energies and pionic decay widths of hea vier double-Lambda hypernuclei, not discovered yet. Finally, we discard the existence of S-1(0) Lambda Lambda bound states provided the Lambda Lambda- Xi N coupling can be neglected. (C) 1999 Elsevier Science B.V.