S-wave pairing of Λ hyperons in dense matter

In this work we calculate the ${}^1{S}_0$ gap energies of Λ hyperons in neutron star matter. The calculation is based on a solution of the BCS gap equation for an effective $G$-matrix parametrization of the Λ-Λ interaction with a nuclear matter background, presented recently by Lanskoy and Yamamoto. We find that a gap energy of a few tenths of a MeV is expected for Λ Fermi momenta up to about $1.3{\mathrm{fm}}^{\mathrm{-}1}.$ Implications for neutron star matter are examined, and suggest the existence of a Λ ${}^1{S}_0$ superfluid between the threshold baryon density for Λ formation and the baryon density where the Λ fraction reaches 15–20 %.