No Arabic abstract
In-medium properties of the low-lying baryons are studied in the quark-meson coupling (QMC) model, focusing on the $Sigma_b$ and $Xi_b$ baryons. It is predicted that the Lorentz-scalar effective mass of $Sigma_b$ becomes smaller than that of $Xi_b$ at moderate nuclear matter density, and as the density increases, namely, $m^*_{Sigma_b} < m^*_{Xi_b}$, although in vacuum $m_{Sigma_b} > m_{Xi_b}$. We also study the effects of the repulsive Lorentz-vector potentials on the excitation energies of these bottom baryons.
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 quarks, as well as at least one light quark. Highlight is the prediction of the bottom baryon Lorentz-scalar effective masses, namely, the Lorentz-scalar effective mass of $Sigma_b$ becomes smaller than that of $Xi_b$ at moderate nuclear matter density, $m^*_{Sigma_b} < m^*_{Xi_b}$, although in vacuum $m_{Sigma_b} > m_{Xi_b}$. We study further the effects of the repulsive Lorentz-vector potentials on the excitation (total) energies of these bottom baryons.
We study the magnetic moments of the octet, low-lying charm, and low-lying bottom baryons with nonzero light quarks in symmetric nuclear matter. This is the first study of estimating the medium modifications of magnetic moments for these low-lying charm and bottom baryons.
Properties of $rho$-meson in symmetric nuclear matter are investigated in a light-front constituent quark model (LFCQM), using the in-medium inputs calculated by the quark-meson coupling (QMC) model. The LFCQM used in this study was already applied for the studies of the electromagnetic properties of $rho$-meson in vacuum, namely, the charge~$G_0$, magnetic~$G_1$, and quadrupole~$G_2$ form factors, electromagnetic charge radius, and electromagnetic decay constant. We predict that the electromagnetic decay constant, charge radius, and quadrupole moment are enhanced as increasing the nuclear matter density, while the magnetic moment is slightly quenched. Furthermore, we predict that the value $Q^2_{rm zero}$, which crosses zero of the charge form factor, $G_0(Q^2_{rm zero})=0$ ($Q^2 = -q^2 > 0$ with $q$ being the four-momentum transfer), decreases as increasing the nuclear matter density.
We revisit the phase diagram of strong-interaction matter for the two-flavor quark-meson model using the Functional Renormalization Group. In contrast to standard mean-field calculations, an unusual phase structure is encountered at low temperatures and large quark chemical potentials. In particular, we identify a regime where the pressure decreases with increasing temperature and discuss possible reasons for this unphysical behavior.
The properties of neutron stars constituted of a crust of hadrons and an internal part of hadrons and kaon condensate are calculated within the quark-meson-coupling model. We have considered stars with nucleons only in the hadron phase and also stars with hyperons as well. The results are compared with the ones obtained from the non-linear Walecka model for the hadronic phase.