Description of Hypernucleus _(ΛΛ)~6He by the ΛΛ_α Model

Based on the ΛΛα model,a variational calculation for the double-Λhypernucleus ΛΛ6He is carried out with the harmonic oscillator formalism.Among thevarious Λ-Λ interactions proposed,the Gaussian type with or without repulsive core ischosen.Their influence on eigenenergy,structure and interparticle correlation is studiedby observing the shape-density.

Phenomenological Analysis of Binding Energies of ■ Hypernuclei

The ground-state(GS)binding energies of the■hyperon in a few known■hyper-nuclei are calculated by solving Schr■dinger and Dirac equations with phenomenological■nu-cleus potential of Woods-Saxon shape.The calculated binding energies are in good agreementwith the experimental values.The optimal well depth of■-nucleus potential is extracted:U■=23.9 MeV.

The interplay of single-particle and collective motions in the low-lying states of ^(21)_(A)Ne with quadrupole-octupole correlations

The beyond mean-field approach for low-lying hypernuclear states is extended by mixing the configurations associated with both single-particle and quadrupole-octupole collective excitations within the generator coordinate method based on a covariant den-sity functional theory.The method is demonstrated in the application to the low-lying states of 21ΛNe,where the configurations with theΛhyperon occupying the first(Λ_(s))and second(Λ_(p))lowest-energy states are considered.The results indicate that the positive-parity states are dominated by theα+^(12)C+α+Λ_(s) structure.In contrast,the low-lying negative-parity states are domi-nated by a strong admixture ofα+16O+Λ_(s) structure andα+12C+α+Λ_(p) structure due to the inclusion of octupole correlations.As a result,the low-lying negative-parity states become much lower than what is expected from the previous studies without the mixing,and the electric multipole transition strengths are significantly quenched.

Beyond mean-field approach for pear-shaped hypernuclei

We develop both relativistic mean field and beyond approaches for hypernuclei with possible quadrupole-octupole deformation or pear-like shapes based on relativistic point-coupling energy density functionals. The symmetries broken in the mean-field states are recovered with parity, particle-number and angular momentum projections. We take_Λ^(21)Ne as an example to illustrate the method, where the Λ hyperon is put on one of the two lowest-energy orbits(labeled as Λ_s, Λ_p), respectively. We find that the Λ hyperon in both cases disfavors the formation of a reflection-asymmetric molecular-like^(16)O+α structure in^(20)Ne, which is consistent with the Nilsson diagram for the hyperon in(β_2, β_3) deformation plane. In particular, we show that the negative-parity states with the configuration^(20)Ne(K~π= 0^-)  Λ_s are close in energy to those with the configuration^(20)Ne(K~π= 0^+)Λ_p, even though they have very different structures. The Λ_s(Λ_p) becomes more and more concentrated around the bottom(top) of the"pear" with the increase of octupole deformation.