Speaker
Description
We study the effect of the isovector-scalar meson a0(980) on the properties of nuclear matter and the neutron star (NS) matter by constructing a parity doublet model with including the a0 meson based on the chiral SU(2)L×SU(2)R symmetry. We also include the ω-ρ mixing contribution to adjust the slope parameter at the saturation. We find that, when the chiral invariant mass of nucleon m0 is smaller than about 800 MeV, the existence of a0(980) enlarges the symmetry energy by strengthening the repulsive ρ meson coupling. On the other hand, for large m0 where the Yukawa coupling of a0(980) to nucleon is small, the symmetry energy is reduced by the effect of ω-ρ mixing. We then construct the equation of state (EoS) of a neutron star matter to obtain the mass-radius relation of NS. We find that, in most choices of m0, the existence of a0(980) stiffens the EoS and makes the radius of NS larger. We then constrain the chiral invariant mass of nucleon from the observational data of NS, and find that 580 MeV≲m0≲860 MeV for L0=57.7 MeV.
