Spin-orbit coupling in Σ-hypernuclei

Single-particle energies of Σ-hyperons in _Σ¹⁶O are calculated within a relativistic mean-field theory. This model predicts a small spin-orbit splitting for Σ-hyperons in _Σ¹⁶O compared to ordinary nucleons in nuclei. Half of the small spin-orbit splitting is due to the anomalous magnetic moment of the Σ-hyperon. K and K¹ exchange terms are negligible. This is to be seen in contrast to a previous quark-model prediction of a strong spin-orbit splitting for hyperons.