arXiv subjects

Nam-Yong Ghim

Publications and source records attributed to Nam-Yong Ghim.

5 recordsLinked to original sources

arXiv2026

Multipole structure of the nucleon tensor form factors

We investigate the multipole structure of the nucleon tensor form factors within the chiral quark-soliton model based on the $1/N_c$ expansion. Extending the previous leading-order analysis~\cite{Ghim:2025gqo}, we include the rotational $1/N_c$ corrections. These corrections provide the leading nonvanishing contributions to the flavor components that are absent at leading order, thereby completing the flavor decomposition of the tensor multipole form factors at the present order. We numerically evaluate the isoscalar tensor charge, the isovector anomalous tensor magnetic moment, and the isoscalar tensor quadrupole moment, obtaining $g_T^{u+d}=0.81$, $κ_T^{u-d}=1.97$, and $E_T^{u+d}(0)=5.98$, respectively. The isoscalar tensor charge and quadrupole moment are mainly governed by the valence-quark contribution, whereas the isovector anomalous tensor magnetic moment receives a sizable Dirac-sea contribution. We also examine the momentum-transfer dependence of the corresponding form factors. They decrease monotonically with increasing $-t$. In particular, the isovector anomalous tensor magnetic form factor shows a pronounced falloff in the small-$|t|$ region, reflecting the importance of the Dirac sea in the tensor dipole structure.

hep-ph↗

arXiv2025

Properties of neutron stars and strangeness-mixed stars from a pion mean-field approach

We investigate the properties of the static neutron stars and strangeness-mixed stars, based on the equations of state derived from a pion mean-field approach. Using the empirical data on the pion-nucleus scattering and bulk properties of nuclear matter, we have already fixed all the parameters in a previous work, where the nucleons and hyperons were shown to be modified in various nuclear medium. In the current work, we first examine the energy and pressure inside a neutron star. We show that the central densities in various neutron stars vary within the range of $(3-4)ρ_0$, where $ρ_0$ is the normal nuclear matter density. The mass-radius relations are obtained and discussed. As the slope parameter for neutron matter increases, the radii of the neutron stars increase with their masses fixed. We also study the strangeness-mixed stars or the hyperon stars using the same sets of the parameters. As the strangeness content of strange matter increases, the binding energy per nucleon is saturated and the corresponding equation of state becomes softened. Consequently, the central densities of the strangeness-mixed stars increase. Assuming that recently observed neutron stars are the strangeness-mixed ones, we find that the central densities increase.

hep-ph↗

arXiv2025

Nucleon tensor form factors at large $N_{c}$

We investigate nucleon tensor form factors in the large-$N_{c}$ limit. In this picture, the nucleon emerges as a state of the $N_c$ valence quarks, which were bound by pion mean fields that were created by the presence of the valence quarks self-consistently. We find that the tensor charge ($g^{u-d}_{T}=0.99$) and the anomalous tensor magnetic moment ($κ^{u+d}_{T}=7.61$) are dominated by valence quarks, while the tensor quadrupole moment ($Q^{u-d}_{T}=-7.02$) shows significant sea quark effects. We examine how these quantities vary as the average size of the pion mean field is changed, showing interpolation between non-relativistic quark and Skyrme limits. We also observe that $g^{u-d}_{T}$ and $κ^{u+d}_{T}$ depend weakly on the pion mass. In contrast, $Q^{u-d}_{T}$ exhibits strong enhancement near the chiral limit. The numerical results are in good agreement with available lattice QCD data and provide predictions for unmeasured quantities.

hep-ph↗

arXiv2022

Medium modification of singly heavy baryons in a pion-mean field approach

We investigate how the masses of singly heavy baryons undergo changes in nuclear matter. The mass spectrum of the singly heavy baryons was successfully described in a pion-mean field approach even with isospin symmetry breaking, based on which we extend the investigation to the medium modification of the singly heavy baryons. Since all dynamical parameters were determined by explaining the mass spectrum of the SU(3) light and singly heavy baryons in free space, we can directly implement the density-dependent functionals for the dynamical parameters, of which the density dependence was already fixed by reproducing the bulk properties of nuclear matter and medium modification of the SU(3) light baryons. We predict and discuss the density dependence of the masses of the singly heavy baryons.

hep-ph↗

arXiv2021

Baryonic matter and the medium modification of the baryon masses

We investigate the properties of baryonic matter within the framework of the in-medium modified chiral soliton model by taking into account the effects of surrounding baryonic environment on the properties of in-medium baryons. The internal parameters of the model are determined based on nuclear phenomenology at nonstrange sector and fitted by reproducing nuclear matter properties near the saturation point. We discuss the equations of state in different nuclear environments such as symmetric nuclear matter, neutron and strange matters. We show that the results for the equations of state are in good agreement with the phenomenology of nuclear matter. We also discuss how the SU(3) baryons masses undergo changes in these various types of nuclear matter.

nucl-th↗