The hyperon superfluidity and the hyperon couplings in neutron stars within the relativistic mean field model

Abstract

A systematic study of the effects of hyperon couplings on hyperon superfluidity is conducted by using the relativistic mean field model. Combining the slope of symmetry energy, the hyperon couplings are determined in two ways -- by the hypernuclear potentials or under the SU(3) symmetry. In either way, the hyperon coupling constants cannot be fixed uniquely but vary within a certain range due to the uncertainties in hypernuclear potentials or the breaking of SU(6) to SU(3) symmetry. When the coupling constants are constrained by the hypernuclear potentials, the pairings of $\Lambda$ and $\Xi^{0,-}$ are strong and they each show little variations. The pairing of $\Sigma^-$ is more sensitive to hyperon potentials and the slope of symmetry energy. Under the SU(3) symmetry, the superfluidity of various hyperons differ significantly. The dependence of the pairings of $\Lambda$ and $\Xi^{0,-}$ on the additional parameters of SU(3) symmetry are the opposite to that of the maximum mass of neutron stars on the additional parameters of SU(3) symmetry, while the pairing of $\Sigma^-$ shows a similar trend in general. These results suggest that the hyperon superfluidity associated with astrophysical processes is an essential window to probe the physics of neutron star cores, the hyperon-hyperon interactions and the SU(3) symmetry. Compared with other hyperons, $\Sigma^-$ could serve as a cleaner glass for this purpose.