Double-Strangeness Five-Body System

We perform theoretical analysis on the structure and decay of a double-strangeness five-body system which consists of 5ΛΛH and 5ΞH states. In this S =−2 five-body system the thresholds of the tΛΛ channel and the αΞ− channel come closer with only 8.51 MeV difference. We treat both bound and resonant states of the three-body channels tΛΛ and tpΞ− by applying a complex rotation method. It is found that there is a bound 5ΛΛH state with 6.3 MeV below the threshold t+Λ+Λ. In the Ξ− channel a resonant 5ΞH state appears at 1.7 MeV below the threshold of α+Ξ−. Though the existence of this state is ensured by the Coulomb interaction, it is a ‘halo’ nuclear state rather than an atomic state as judged from its size. The conversion width of this state is 0.2 MeV which is extremely narrow. It is also found that Ξ mixing into the 5ΛΛH ground state is small with 1.0%. For the 5ΛΛH state, the weak decay to the α+Σ− final state produces a high mono-energetic Σ− with branching ratio of 5.5%. Thus the Σ− with discrete energy would become a clear signature of the forming of the ΛΛ hypernucleus.