Altas Energias

K. Tsushima

Phys. Rev. D 99, 014026 – Published 17 January 2019

Abstract

In-medium properties of the low-lying strange, charm, and bottom baryons in symmetric nuclear matter are studied in the quark-meson coupling (QMC) model. Results for the Lorentz-scalar effective masses, mean field potentials felt by the light quarks in the baryons, in-medium bag radii, and the lowest mode bag eigenvalues are presented for those calculated using the updated data. This study completes the in-medium properties of the low-lying baryons in symmetric nuclear matter in the QMC model, for the strange, charm, and bottom baryons which contain one or two strange, one charm, or one bottom quark, as well as at least one light quark. The highlight is the prediction of the bottom baryon Lorentz-scalar effective masses; namely, the Lorentz-scalar effective mass of Σb becomes smaller than that of Ξb at moderate nuclear matter density, m∗Σb<m∗Ξb, although in vacuum mΣb>mΞb. We study further the effects of the repulsive Lorentz-vector potentials on the excitation (total) energies of these bottom baryons.

10.1103/PhysRevD.99.014026

Fábio L. Braghin

Fábio L. Braghin

Phys. Rev. D 99, 014001

Abstract

Form factors for pion interactions with constituent quarks are investigated as the leading effective couplings obtained from a one-loop background field method applied to a global color model. Two pion field definitions are considered and the resulting eleven form factors are expressed in terms of components of the quark and gluon propagators that compose only two momentum-dependent functions. A momentum-dependent Goldberger-Treiman relation is also obtained as one of the ratios between the form factors. The resulting form factors with pion momenta up to 1.5 GeV are exhibited for different quark effective masses and two different nonperturbative gluon propagators and they present similar behavior to fittings of experimental data from nucleons form factors. The corresponding pseudoscalar averaged quadratic radii (a.q.r.) and correction to the axial a.q.r. are presented as functions of the sea quark effective mass, being equal, respectively, to the scalar and vector ones at the present level of calculation.

10.1103/PhysRevD.99.014001