Low-lying states of A = 6 hypernuclear doublets (6ΛHe and 6ΛLi) and A = 7 triplets (7ΛHe, 7ΛLi, and 7ΛBe) are studied with an accurate three-body model calculation in which all the rearrangement Jacobian coordinates are equally taken into account. Since most of the hypernuclear states concerned are weakly bound states, focus is placed on the binding energies with respect to the particle breakup thresholds and on the density distributions in the surface and exterior regions. With the α + Λ + N model, the observed binding energies of the ground states of 6ΛHe and 6ΛLi are well reproduced. 6ΛHe is found to have a three-layer structure of the matter distribution: the α nuclear core, a Λ skin, and a neutron halo. The A = 7 hypernuclei are shown to be well described with the 5ΛHe + N+N model. Using a realistic NN interaction, the correlation between the valence nucleons is fully taken into account; this is essentially important to make the proton-rich three-body system 7ΛBe = 5ΛHe + p+p bound although none of the two-body subsystems is bound. The observed binding energies of 7ΛLi and 7ΛBe are well reproduced, and energies are predicted for 7ΛHe whose core nucleus is a neutron halo nucleus, 6He. We discuss the validity of the assumption of frozen deuterons adopted in the previous α + d + Λ models for the T = 0 states of 7ΛLi.
ASJC Scopus subject areas
- Nuclear and High Energy Physics