Spin and pseudospin symmetries in the single- Λ spectrum

Abstract

We explore spin and pseudospin symmetries in the single-$\mathrm{\ensuremath{\Lambda}}$ spectrum within the framework of relativistic mean-field theory. We find that the spin symmetry of the single-$\mathrm{\ensuremath{\Lambda}}$ spectrum maintains, which is consistent with experimental results of small spin-orbit splitting, whereas the approximate pseudospin symmetry is quite similar to that of nucleons. More interestingly, the $\ensuremath{\omega}\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}$ tensor coupling has opposite effects on these symmetries which makes the spin symmetry better but the pseudospin symmetry worse. This can be understood by the negative value of the $\ensuremath{\omega}\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}$ tensor potential, which reduces the spin-orbit potential while increasing the pseudospin-orbit potential.