Compact star and compact star matter properties from a baryonic extended linear sigma model with explicit chiral symmetry breaking

Based on a baryonic extended linear sigma model including explicit chiral symmetry breaking effect, the structure of neutron star with the emergence of hyperons is investigated using the relativistic mean field approximation. It’s found that, except the lightest scalar meson $\sigma$ whose structure is not well understood so far, the vacuum mass spectra of relevant hadrons and NM properties around saturation density can be well reproduced. Nevertheless, we found that, to have a realistic mass-radius relation of neutron stars, the $\pi N$ sigma term ${\sigma }_{\pi N}$, which denotes the contribution of explicit symmetry breaking, should deviate from its empirical values at vacuum. Specifically, ${\sigma }_{\pi N}\sim -600$ MeV, rather than $(32-89)\mathrm{M}\mathrm{e}\mathrm{V}$ at vacuum. With an appropriate choice of ${\sigma }_{\pi N}$ and $K(n_0)$, our framework can give a more data favored mass-radius relation of neutron stars with the emergence of hyperons. The effect of explicit symmetry breaking at densities is hoped to provide a new insight to the relation between microscopic symmetries in medium and macroscopic phenomena.