Few-body aspects of light hypernuclei Original Research Article

Three- and four-body structure calculations of single Λ hypernuclei such as Λ7He, Λ9Be and Λ13C and double Λ hypernuclei such as ΛΛ4H, ΛΛ7He, ΛΛ7Li, ΛΛ8Li, ΛΛ9Li, ΛΛ9Be and ΛΛ10Be are discussed. The energy levels of Λ7He whose core is a famous halo nucleus, Λ6He, are predicted based on Λ5He + 2N three-body model. In the microscopic 2α + Λ(3α + Λ) model for Λ9Be(Λ13C), we predict the spin-orbit splittings of 5/21+−3/21+ in Λ9Be and 3/21−−1/21− in Λ13C to be 0.08–0.16 MeV and 0.39–0.78 MeV, respectively, with the use of OBE-model NSC97a ∼f. On the other hand quark-model ΛN spin-orbit force gives rise to half of the splittings of the smallest OBE-model prediction. The experimental data were reported to be 31.4−3.6+2.5 keV for Λ9Be and to be 152 ± 54 ± 36 keV for Λ13C. By performing four-body calculation of ΛΛ4H with both NNΛΛ and NNNΞ channels, we show that the ΛΛ − ΞN coupling potential plays an important role in making ΛΛ4H. Energy levels of the double-Λ hypernuclei, ΛΛ7He, ΛΛ7Li, ΛΛ8Li, ΛΛ9Li, ΛΛ9Be and ΛΛ10Be are predicted on the basis of an α + x + Λ + Λ four-body model, where x = n,p,d,t3He and α, respectively.