Relativistic mean-field approach for Lambda, Xi, and Sigma hypernuclei

We systematically study the properties of single-Lambda, Xi, and Sigma 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 Ca-40, we investigate its mean-field potentials, single-hyperon levels, density distributions, and binding energies, where the consequences of introducing different types of hyperons (Lambda, Xi(0,-) and Sigma(+,0,-)) are examined. In general, the Lambda and Sigma(0) hyperons show similar behaviors in bulk properties since both of them are electroneutral and have similar coupling constants; Xi(0) hyperon owns the shallowest mean-field potential well with the most extended density distribution; and Coulomb interactions play vital roles in the charged Xi(-), Sigma(-), and Sigma(+) hyperons. As a result, those hyperons have different impurity effects on the nuclear core Ca-40. The omega YY tensor couplings are included and show remarkable effects on the spin-orbit splitting which even change the level ordering of Xi hyperon. Finally, the single-hyperon binding energy of hypernuclei generally increases with the mass number. However, there is a turning point for Sigma(+) hypernuclei at Nb-91(Sigma+) where the binding energy begins to decrease. This is mainly due to the increasing Coulomb repulsive potential at large proton numbers.