Single-particle spin–orbit strengths of the nucleon and hyperons by [formula omitted] quark-model

Abstract

The quark-model hyperon–nucleon interaction suggests an important antisymmetric spin–orbit component. It is generated from a color analogue of the Fermi–Breit interaction dominating in the one-gluon exchange process between quarks. We discuss the strength S B of the single-particle spin–orbit potential, following the Scheerbaum's prescription. Using the SU 6 quark-model baryon–baryon interaction which was recently developed by the Kyoto–Niigata group, we calculate NN, ΛN and ΣN G-matrices in symmetric nuclear matter and apply them to estimate the strength S B . The ratio of S B to the nucleon strength S N∼−40 MeV fm 5 is S Λ/S N∼1/5 and S Σ/S N∼1/2 in the Born approximation. The G-matrix calculation of the model FSS modifies S Λ to S Λ/S N∼1/12 . For S N and S Σ , the effect of the short-range correlation is comparatively weak against meson-exchange potentials with a short-range repulsive core. The significant reduction of the Λ single-particle potential arises from the combined effect of the antisymmetric LS force, the flavor-symmetry breaking originating from the strange to up-down quark-mass difference, as well as the effect of the short-range correlation. The density dependence of S B is also examined.