Energy levels of the double-Λ hypernuclei ΛΛ7 He, ΛΛ7 Li, ΛΛ8 Li, ΛΛ9 Li, ΛΛ9 Be, and ΛΛ10 Be are predicted on the basis of an α+x+Λ+Λ four-body model, where x = n, p, d, t, 3He, and α, respectively. Interactions between the constituent particles are determined so as to reproduce reasonably the observed low-energy properties of the α+x nuclei (5He, 5Li, 6Li, 7Li, 7Be, 8Be) and the existing data for Λ-binding energies of the x + Λ and α+x+Λ systems (Λ3H, Λ4H, Λ5He, Λ6He, Λ6Li, Λ8Li, Λ8Be, Λ9 Be). An effective ΛΛ interaction is constructed so as to reproduce, within the α+Λ+Λ model, the BΛΛ of ΛΛ6 He, which was extracted from the emulsion experiment, the NAGARA event. With no adjustable parameters for the α+x+Λ+Λ system, BΛΛ of ground and bound excited states of the double-Λ hypernuclei with A=7-10 are calculated within the Gaussian-basis coupled-rearrangement-channel method. The Demachi-Yanagi event, identified recently as ΛΛ10Be, is interpreted as an observation of its 2+ excited state on the basis of the present calculation. Structural changes in the α + x core nuclei, due to the interaction of the Λ particles, are found to be substantial, and these play an important role in estimating the ΛΛ bond energies of those hypernuclei.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics