Fully Coupled Channel Approach to Doubly Strange s-Shell Hypernuclei

We describe ab initio calculations of doubly strange, S=-2, s-shell hypernuclei (ΛΛ4H, ΛΛ5H, ΛΛ5He, and ΛΛ6He) as a first attempt to explore the few-body problem of the full-coupled channel scheme for these systems. The wave function includes ΛΛ, ΛΣ, NΞ, and ΣΣ channels. Minnesota NN, D2' YN, and simulated YY potentials based on the Nijmegen hard-core model are used. Bound-state solutions of these systems are obtained. We find that a set of phenomenological B8B8 interactions among the octet baryons in S=0,-1, and -2 sectors, which is consistent with all of the available experimental binding energies of S=0,-1, and -2 s-shell (hyper)nuclei, can predict a particle stable bound state of ΛΛ4H. For ΛΛ5H and ΛΛ5He, ΛN-ΣN and ΞN-ΛΣ potentials significantly affect the net ΛΛ-NΞ coupling, and a large Ξ probability is obtained even for a weaker ΛΛ-NΞ potential