Relativistic σ-ω mean-field theory for hyperons from a quark model

We suggest a phenomenological description of hypernuclear {σ}-{ω} Dirac mean-field theory, where the meson-baryon vertices are based on the quark model with relativistic corrections. While the model is shown to be in agreement with the {σ}-{ω} model for regular nuclei, large tensor {ω}YY couplings are derived for {ω}-hyperon vertices. This coupling, which is negligible for nucleons, is capable of resolving the problem of the small spin-orbit interaction in {Λ} hypernuclei within the Dirac approach, as was recently shown independently by Jennings. Our model explains the available data. It can also be the basis for more systematic theoretical studies. Predictions are thus presented for {Σ} and {Ξ} hypernuclei. Further improvements of the model are discussed.