Λ, Σ, and Ξ hyperons in neutron matter

Hyperon single-particle potentials are calculated in pure neutron matter in the framework of the lowest-order Brueckner theory, using two recent baryon-baryon interactions, the SU6 quark-model potential and the potential derived from the chiral effective field theory. These properties are important for understanding neutron star matter on the basis of underlying baryon-baryon interactions. Because the calculated potential of Σ− is strongly repulsive and that of Ξ− is also repulsive, these hyperons are unlikely to appear in neutron star matter. The Λ potential is attractive enough to appear in high neutron matter as has been commonly expected in microscopic calculations. After showing important contributions of three-nucleon forces in neutron matter, analogous repulsive contributions to the Λ potential from the Σ⁎ excitation are estimated by evaluating second-order diagrams.