Possibility of pairing and its dependence on background density in a relativistic Hartree-Bogoliubov model

Tanigawa, Tomonori; Matsuzaki, Masayuki*; Chiba, Satoshi

We calculate a pairing gap in binary mixed matter of nucleons and hyperons within the relativistic Hartree-Bogoliubov model since a recent experiment suggests a weaker attraction than before, which has a significant impact on properties of neutron stars in various aspects. Lambda hyperons to be paired up are immersed in background nucleons in normal state. A phenomenological interaction, which is derived relativistically from the Lagrangian of the system, is adopted to the gap equation. It is found that at background density the pairing gap is very small, and that denser background makes it rapidly suppressed. This result suggests a mechanism, specific to mixed matter dealt with relativistic models, of its dependence on the nucleon density.