Wednesday, July 17, 2013

1307.4154 (J. N. Hu et al.)

Extended quark mean-field model for neutron stars: Toward a broken flavor SU(3) symmetry    [PDF]

J. N. Hu, A. Li, H. Toki, W. Zuo
We extend the quark mean-field (QMF) model to strangeness freedom to study the properties of hyperons ($\Lambda,\Sigma,\Xi$) in infinite baryonic matter and neutron star properties. The baryon-scalar meson couplings in QMF model are determined self-consistently from the quark level, where the quark confinement is taken into account in terms of a scalar-vector harmonic oscillator potential. The strength of such confinement potential for $u,d$ quarks is constrained by the properties of finite nuclei, while the one for $s$ quark is limited by the properties of nuclei with a $\Lambda$ hyperon. These two strengths are not same, which represents the SU(3) symmetry breaking effectively in QMF model. With these baryon-scalar meson coupling constants, the single baryon potentials are obtained, where all of three hyperon potentials are attractive at nuclear saturation density. The potentials for $\Lambda$ and $\Sigma$ are difference about 5 MeV at the saturation density, which shows this SU(3) symmetry breaking approaches 20% in the extended QMF model. Finally we obtain a neutron star maximum mass of $1.59 M_{\odot}$ with $\Lambda$, $\Sigma$ and $\Xi$ hyperons within the present model. This value is far from the recently measured pulsar mass, consistent with the convectional relativistic mean field theory and also the microscopic studies based on developed realistic baryon-baryon interactions.
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