arXiv subjects

Ki-Hoon Hong

Publications and source records attributed to Ki-Hoon Hong.

7 recordsLinked to original sources

arXiv2026

Transverse distributions of the energy-momentum tensor for a spin-$3/2$ baryon

We develop a multipole description of transverse distributions of the energy-momentum tensor for a spin-$3/2$ baryon in frames connected by a longitudinal boost. In the transverse Breit frame, the $T^{00}$, $T^{03}$, and $T^{33}$ matrix elements are expressed through seven multipole form factors for energy, angular momentum, and stress. At finite longitudinal momentum, we factorize the Lorentz mixing of these three components from the spin-$3/2$ Wigner rotations of the external states. The resulting elastic-frame matrix elements contain six transverse multipoles, whose Fourier transforms define the distributions of energy, longitudinal momentum, and longitudinal momentum flux. We also calculate $T^{++}$, $T^{+-}$, and $T^{--}$ directly with light-front Rarita-Schwinger spinors. The elastic-frame construction provides a continuous interpolation from the transverse Breit frame to the infinite-momentum frame. In this limit, the Wigner rotation becomes the Melosh rotation, and the leading elastic-frame matrix elements reproduce the corresponding light-front results. Using the $\Delta$-baryon gravitational form factors obtained in the Skyrme model as a representative numerical input, we find that the energy distribution is dominated by the energy monopole defined in the transverse Breit frame and changes only weakly under longitudinal boosts. Through boost mixing, this monopole provides the dominant contribution to the longitudinal momentum distribution and its flux at finite $P_z$. For a longitudinally polarized spin-$3/2$ target, the distributions contain only the monopole contributions, whereas those of a transversely polarized target exhibit spin-dependent quadrupole and octupole deformations and a dipole that shifts their maxima.

hep-ph↗

arXiv2026

Heavy mesons from the QCD instanton vacuum beyond the static limit

We study pseudoscalar heavy mesons in the QCD instanton vacuum beyond the static limit. Finite-mass effects in the heavy-light loop are encoded in a separable effective vertex built from a profile function $\phi(\vec{p})$, kept distinct from the static Wilson-line form factor $F_Q^{(\infty)}(\vec{q})$ of the $m_Q\to\infty$ limit. The pseudoscalar two-point function fixes the residual mass $\Lambda$ and the residue-normalized meson-quark coupling, from which we evaluate the decay constant, the spin-independent kinetic matrix element, and the zero-recoil slope of the Isgur-Wise function at order $1/m_Q$. The subleading calculation is restricted to the kinetic (derivative) part of the HQET operators. For a representative vertex calibrated to the $B$-meson decay constant and the spin-averaged $B$-meson mass, we obtain $f_B = 186.8$~MeV, $\Lambda = 184.5$~MeV, $m_b^{\mathrm{eff}} = 5.04$~GeV, $\lambda_1^{(\partial)} = -0.922~\mathrm{GeV}^2$, and $\rho_{\mathrm{IW}}^2 = 1.105$. The kinetic contribution yields a mass shift of order $\Lambda/2$ and a sizable $1/m_Q$ current correction, indicating that the spin-independent nonperturbative $1/m_Q$ sector is a sensitive probe of the finite-mass heavy-light vertex.

hep-ph↗

arXiv2024

Heavy-light quark systems from the QCD instanton vacuum: $N_f=1$ light flavor case

We investigate heavy-light quark systems within the framework of the QCD instanton vacuum, focusing on the $N_f = 1$ light flavor case. We derive an effective heavy-light quark interaction from the low-energy QCD partition function and construct a heavy-meson effective Lagrangian. The physical residual mass of heavy mesons, $\Lambda$, is determined by employing compositeness and normalization conditions. We calculate the masses of $D$ and $B$ mesons and their weak decay constants to the leading order and next-to-leading order in the $1/m_Q$ expansion. The current results for $f_D$ and $f_B$ are in good agreement with recent lattice QCD data and PDG average values.

hep-ph↗

arXiv2023

Two-dimensional charge distributions of the $Δ$ baryon: Interpolation between the nonrelativistic and ultrarelativistic limit

We investigate how the charge distributions of both the unpolarized and transversely polarized $Δ$ baryon change as the longitudinal momentum~($P_{z}$) of the $Δ$ baryon increases from $P_{z}=0$ to $P_{z}=\infty$ in a Wigner phase-space perspective. When the $Δ$ baryon is longitudinally polarized, its two-dimensional charge distribution is kept to be spherically symmetric with $P_{z}$ varied, whereas when the $Δ$ baryon is transversely polarized along the $x$-axis, the quadrupole contribution emerges at the rest frame ($P_{z}=0$). When $P_{z}$ grows, the electric dipole and octupole moments are induced. The induced dipole moment dominates over other higher multipole contributions and governs the deformation of the charge distribution of the $Δ$ baryon.

hep-ph↗

arXiv2022

Instanton effects on electromagnetic transitions of charmonia

We investigate the mass spectrum and electromagnetic transitions of charmonia, emphasizing the instanton effects on them. The heavy-quark potential consists of the Coulomb-like potential from one-gluon exchange and the linear confining potential. We introduce the nonperturbative heavy-quark potential derived from the instanton vacuum. We also consider the screened confining potential, which better describes the electromagnetic decays of higher excited states. Using this improved heavy-quark potential, we compute the mass spectrum and electromagnetic decays of the charmonia. Focusing on the instanton effects, we discuss the results compared with the experimental data and those from other works. The instanton effects are marginal on the electromagnetic decays of charmonia.

hep-ph↗

arXiv2019

Modification of hyperon masses in nuclear matter

We discuss the properties of baryons within the framework of the in-medium modified SU(3) Skyrme model. The modification is performed by a minimal way, the medium functionals in the SU(2) sector being introduced. These functionals are then related to nuclear matter properties near the saturation point. The modifications in the SU(3) sector are performed with the additional changes of kaon properties in nuclear matter. The results show that the properties of baryons in the strange sector are sensitive to the in-medium modifications of the kaon properties. The consistency of the in-medium modifications of hadron properties in the present approach with other model approaches and phenomenological indications is also discussed.

nucl-th↗

arXiv2018

In-medium properties of SU(3) baryons

Changes of baryon properties in nuclear matter are investigated within the framework of an in-medium modified SU(3) Skyrme model. Introducing the medium functionals in the SU(2) sector and considering the alteration of kaon properties in nuclear medium, we are able to examine the medium modification of the nucleon and hyperons. The functionals introduced in the SU(2) sector are related to ordinary nuclear matter properties near the saturation point. The results indicate that the changes of the baryon properties in the strange sector are strongly correlated with the in-medium properties of kaons.

nucl-th↗