Possible Lightest Ξ Hypernucleus with Modern ΞN Interactions

Experimental evidence exists that the Ξ-nucleus interaction is attractive. We search for NNΞ and NNNΞ bound systems on the basis of the AV8 NN potential combined with either a phenomenological Nijmegen ΞN potential or a first principles HAL QCD ΞN potential. The binding energies of the three-body and four-body systems (below the d+Ξ and H3/He3+Ξ thresholds, respectively) are calculated by a high precision variational approach, the Gaussian expansion method. Although the two ΞN potentials have significantly different isospin (T) and spin (S) dependence, the NNNΞ system with quantum numbers (T=0, Jπ=1+) appears to be bound (one deep for Nijmegen and one shallow for HAL QCD) below the H3/He3+Ξ threshold. Experimental implications for such a state are discussed.