Skyrme型NΛ相互作用下超越平均场模型的Λ超核研究

Study of Λ Hypernuclei Using the Beyond-mean-field Approach with Skyrme-type NΛ Interaction

使用超越平均场Skyrme-Hartree-Fock(SHF)模型对_Λ~9Be,_(ΛΛ)^(10)Be,_Λ^(13)C和_Λ^(21)Ne进行计算,采用SLy4参数组的Skyrme力作为NN相互作用力,采用最近提出的SLL4参数组的Skyrme力作为NΛ相互作用。计算中包含了超子的自旋-轨道力以再现单粒子态的自旋-轨道能级分裂和不交叉效应,并采用BCS方法处理对力。讨论了不同组态超核的相关性质,包含^(12)C?Λ[000]1/2^+,^(12)C?Λ[110]1/2^-,^(12)C?Λ[101]3/2^-和^(12)C?Λ[101]1/2^-及~8Be?Λ[000]1/2^+,~8Be?Λ[110]1/2^-,~8Be?Λ[101]3/2^-和~8Be?Λ[101]1/2^-。计算了_Λ~9Be,_Λ^(13)C的低激发能谱并与实验值进行了比较。结果表明,采用的超越平均场SHF模型能很好地再现Λ超子占据sΛ轨道的正宇称能级。对8Be的计算结果表明该模型可以很好地再现8Be的集团结构,可以得出_Λ~9Be的真实超核态能级和9Be类似态。对_Λ~9Be及13ΛC的计算均再现了自旋双重态(3/2+,5/2+),但是得到的双重态能级差依然与实验值有出入。此外,对于上述超核体系均在Λ超子占据Λ[000]1/2^+轨道时产生了收缩效应。还对_Λ^(21)Ne进行了计算并和超越平均场RMF模型计算结果进行比较,发现两者计算结果虽有细节上的出入,但是结果基本一致。

The beyond-mean-field Skyrme-Hartree-Fock approach is adopted to investigate the properties of Λ9Be,ΛΛ10Be,Λ13C and Λ21Ne. The nucleon-nucleon(NN) interaction SLy4 and the nucleon-hyperon(NΛ) interaction Skyrme-type SLL4 are used. The spin-orbit force of hyperon is included to show the spin-orbit splitting and non-crossing effect with BCS method to deal with pairing force. Energies of different configurations, such as 12CΛ[000]1/2+,12CΛ[110]1/2-,12C■Λ[101]3/2-,12C■Λ[101]1/2-,8Be■Λ[000]1/2+,8BeΛ[110]1/2-,8Be■Λ[101]3/2- and 8Be■Λ[101]1/2- are given and used to study the effects of Λ occupying different orbitals.The calculated energy spectra, including both positive-and negative-parity levels, are given and compared to the experimental data. The observed positive-parity spin-doublet(3/2+,5/2+) are successfully reproduced, but the energy difference needs further investigation. The two well known band structures corresponding to the genuine hypernuclear states and the 9Be-analog states are also obtained and compared with the observed ones. The shrinkage effect of Λ occupying Λ[000]1/2+ is investigated through the density distributions of nuclear core. And finally the calculation results of Λ21Ne are given and compared with the results of RMF method, which are nearly the same but with differences in some details.