Relativistic mean-field approach for Λ,Ξ, and Σ hypernuclei

We systematically study the properties of single-Λ,Ξ, and Σ hypernuclei within the framework of relativistic mean-field model. The YN coupling constants are constrained according to the experimental data and previous theoretical efforts. By adding a hyperon to Ca40, we investigate its mean-field potentials, single-hyperon levels, density distributions, and binding energies, where the consequences of introducing different types of hyperons (Λ,Ξ0,−, and Σ+,0,−) are examined. In general, the Λ and Σ0 hyperons show similar behaviors in bulk properties since both of them are electroneutral and have similar coupling constants; Ξ0 hyperon owns the shallowest mean-field potential well with the most extended density distribution; and Coulomb interactions play vital roles in the charged Ξ−,Σ−, and Σ+ hyperons. As a result, those hyperons have different impurity effects on the nuclear core Ca40. The ωYY tensor couplings are included and show remarkable effects on the spin-orbit splitting which even change the level ordering of Ξ hyperon. Finally, the single-hyperon binding energy of hypernuclei generally increases with the mass number. However, there is a turning point for Σ+ hypernuclei at NbΣ+91 where the binding energy begins to decrease. This is mainly due to the increasing Coulomb repulsive potential at large proton numbers.