arXiv subjects

Hyun-Chul Kim

Publications and source records attributed to Hyun-Chul Kim.

At least 91 records · Page 5Linked to original sources

arXiv2018

Mass spectra of heavy mesons with instanton effects

We investigate the mass spectra of ordinary heavy mesons, based on a nonrelativistic potential approach. The heavy-light quark potential contains the Coulomb-type potential arising from one-gluon exchange, the confining potential, and the instanton-induced nonperturbative local heavy-light quark potential. All parameters are theoretically constrained and fixed. We carefully examine the effects from the instanton vacuum. Within the present form of the local potential from the instanton vacuum, we conclude that the instanton effects are rather marginal on the charmed mesons.

hep-ph↗

arXiv2018

Excited $Ω$'s as heavy pentaquarks

We briefly summarize recent works on the identification of the excited $Ω_c$'s found by the LHCb Collaboration. Within the framework of a pion mean-field approach, the following scenario is the most favorable: While three of the excited $Ω_c$'s belong to the excited baryon sextet, two of them with the smaller decay widths can be identified as the members of the anti-decapentaplet which is one of the lowest-lying representations. It implies that these two $Ω_c$'s, i.e. $Ω(3050)$ and $Ω(3119)$ are most probably the exotic heavy pentaquark baryons.

hep-ph↗

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↗

arXiv2018

Electromagnetic properties of singly heavy baryons

In this presentation, we summarize selectively recent results of the electromagnetic form factors of singly heavy baryons with spin 1/2 and related quantities, which were derived within a framework of the self-consistent chiral quark-soliton model. The results are compared with those from the lattice QCD and their physical implications are discussed.

hep-ph↗

arXiv2018

Effects of nucleon resonances on $η$ photoproduction off the neutron reexamined

We investigate $η$ photoproduction off the neutron target, i.e., $γn \to ηn$, employing an effective Lagrangian method combining with a Regge approach. As a background, we consider nucleon exchange in the $s$-channel diagram and $ρ$- and $ω$-meson Regge trajectories in the $t$ channel. The role of nucleon resonances given in the Review of Particle Data Group in the range of $W \approx 1500 - 2100$ MeV and the narrow nucleon resonance $N(1685,1/2^+)$ is extensively studied. The numerical results of the total and differential cross sections, double polarization observable $E$, and helicity-dependent cross sections $σ_{1/2}$, $σ_{3/2}$ are found to be in qualitative agreement with the recent A2 experimental data. The predictions of the beam asymmetry are also given.

hep-ph↗

arXiv2018

$K^0Λ$ photoproduction off the neutron with nucleon resonances

We investigate kaon photoproduction off the neutron target, i.e., $γn \to K^0 Λ$, focusing on the role of nucleon resonances given in the Review of Particle Data Group in the range of $\sqrt{s} \approx 1600 - 2200$ MeV. We employ an effective Lagrangian method and a Regge approach. The strong couplings of nucleon resonances with $KΛ$ vertices are constrained by quark model predictions. The numerical results of the total and differential cross sections are found to be in qualitative agreement with the recent CLAS and FOREST experimental data. We discuss the effects of the narrow nucleon resonance $N(1685,1/2^+)$ on both the total and differential cross sections near the threshold energy. In addition, we present the results of the beam asymmetry as a prediction.

hep-ph↗

arXiv2018

Mass spectra of singly heavy baryons in a self-consistent chiral quark-soliton model

We investigate the mass spectra of the lowest-lying singly heavy baryons, based on the self-consistent chiral quark-soliton model. We take into account the rotational $1/N_c$ and strange current quark mass ($m_{\mathrm{s}}$) corrections. Regarding $m_{\mathrm{s}}$ as a small perturbation, we expand the effective chiral action to the second order with respect to $m_{s}$. The mass spectra of heavy baryons are computed and compared with the experimental data. Fitting the classical masses of the heavy baryon to the center mass of each representation, we determine the masses of all the lowest-lying singly heavy baryons. We predict the mass of the $Ω_b^*$ baryon to be 6081.9 MeV, when the second-order $m_{\mathrm{s}}$ corrections are included.

hep-ph↗

arXiv2018

Meson-baryon coupling constants of the SU(3) baryons with flavor SU(3) symmetry breaking

We investigate the strong coupling constants for the baryon octet-octet, decuplet-octet, and decuplet-decuplet vertices with pseudoscalar mesons within a general framework of the chiral quark-soliton model, taking into account the effects of flavor SU(3) symmetry breaking to linear order in the expansion of the strange current quark mass. All relevant dynamical parameters are fixed by using the experimental data on hyperon semileptonic decays and the singlet axial-vector constant of the nucleon. The results of the strong coupling constants for the baryon octet and the pseudoscalar meson octet are compared with those determined from the Jülich-Bonn potential and the Nijmegen extended soft-core potential for hyperon-nucleon scattering. The results of the strong decay widths of the baryon decuplet are in good agreement with the experimental data. The effects of $SU_f(3)$ symmetry breaking are sizable on the $η'$ coupling constants. We predict also the strong coupling constants for the $Ω$ baryons.

hep-ph↗

arXiv2018

Electromagnetic form factors of singly heavy baryons in the self-consistent SU(3) chiral quark-soliton model

The self-consistent chiral quark-soliton model is a relativistic pion mean-field approach in the large $N_c$ limit, which describes both light and heavy baryons on an equal footing. In the limit of the infinitely heavy mass of the heavy quark, a heavy baryon can be regarded as $N_c-1$ valence quarks bound by the pion mean fields, leaving the heavy quark as a color static source. The structure of the heavy baryon in this scheme is mainly governed by the light-quark degrees of freedom. Based on this framework, we evaluate the electromagnetic form factors of the lowest-lying heavy baryons. The rotational $1/N_c$ and strange current quark mass corrections in linear order are considered. We discuss the electric charge and magnetic densities of heavy baryons in comparison with those of the nucleons. The results of the electric charge radii of the positive-charged heavy baryons show explicitly that the heavy baryon is a compact object. The electric form factors are presented. The form factor of $Σ_c^{++}$ is compared with that from a lattice QCD. We also discuss the results of the magnetic form factors. The magnetic moments of the baryon sextet with spin 1/2 and the magnetic radii are compared with other works and the lattice data.

hep-ph↗

arXiv2018

Heavy baryons in a pion mean-field approach: A brief review

We review in this paper a series of recent works on properties of singly heavy baryons, based on a pion mean-field approach. In the limit of an infinitely heavy-quark mass, the heavy quark inside a heavy baryon can be regarded as a static color source. In this limit, a heavy baryon can be viewed as $N_c-1$ valence quarks bound by the pion mean fields which are created self-consistently by the presence of the $N_c$ valence quarks. We show that this mean-field approach can successfully describe the masses and the magnetic moments of the lowest-lying singly heavy baryons, using all the parameters fixed in the light-baryon sector except for the hyperfine spin-spin interactions. We also review a recent work on identifying the newly found excited $Ω_c$ baryons reported by the LHCb Collaboration. We discuss possible scenarios to identify them. Finally, we give a future perspective on this pion mean-field approach.

hep-ph↗

arXiv2018

Magnetic moments of the lowest-lying singly heavy baryons

A light baryon is viewed as $N_c$ valence quarks bound by meson mean fields in the large $N_c$ limit. In much the same way a singly heavy baryon is regarded as $N_c-1$ valence quarks bound by the same mean fields, which makes it possible to use the properties of light baryons to investigate those of the heavy baryons. A heavy quark being regarded as a static color source in the limit of the infinitely heavy quark mass, the magnetic moments of the heavy baryon are determined entirely by the chiral soliton consisting of a light-quark pair. The magnetic moments of the baryon sextet are obtained by using the parameters fixed in the light-baryon sector. In this mean-field approach, the numerical results of the magnetic moments of the baryon sextet with spin $3/2$ are just 3/2 larger than those with spin $1/2$. The magnetic moments of the bottom baryons are the same as those of the corresponding charmed baryons.

hep-ph↗

arXiv2017

Flavour structure of the nucleon electromagnetic form factors and transverse charge densities in the chiral quark-soliton model

We investigate the flavour decomposition of the electromagnetic form factors of the nucleon, based on the chiral quark-soliton model ($χ$QSM) with symmetry-conserving quantisation. We consider the rotational $1/N_c$ and linear strange-quark mass ($m_s$) corrections. We discuss the results of the flavour-decomposed electromagnetic form factors in comparison with the recent experimental data. In order to see the effects of the strange quark, we compare the SU(3) results with those of SU(2). We finally discuss the transverse charge densities for both unpolarised and polarised nucleons. The transverse charge density inside a neutron turns out to be negative in the vicinity of the centre within the SU(3) $χ$QSM, which can be explained by the contribution of the strange quark.

hep-ph↗

arXiv2017

Strong decays of exotic and non-exotic heavy baryons in the chiral quark-soliton model

In the large $N_c$ limit both heavy and light baryons are described by the universal mean field, which allows us to relate the properties of heavy baryons to light ones. With the only input from the decays of light octet baryons (due to the universality of the chiral mean field), excellent description of strong decays of both charm and bottom sextets is obtained. The parameter-free prediction for the widths of exotic anti-decapentaplet ($\overline{\boldsymbol{15}}$) baryons is also made. The exotic heavy baryons should be anomalously narrow despite of large phase space available. In particular, the widths of $Ω_c(3050)$ and $Ω_c(3119)$, interpreted as members of $\overline{\boldsymbol{15}}$-plet, are very small: 0.48~MeV and 1.12~MeV respectivly. This result is in very good agreement with the measurements of the LHCb Collaboration and provides natural and parameter free explanation of the LHCb observation that $Ω_c(3050)$ and $Ω_c(3119)$ have anomalously small widths among five recently observed states.

hep-ph↗

arXiv2017

Possibility of the existence of charmed exotica

We employ the chiral quark-soliton model to describe excited baryons with one heavy quark. Identifying known charmed baryons with multiplets allowed by the model, we argue that apart from regular excitations of the ground state multiplets, some of recently reported by the LHCb collaboration narrow $Ω^{0}_{c}$ states, may correspond to the exotic pentaquarks. This interpretation can be easily verified experimentally, since exotic $Ω^{0}_{c}$ states -- contrary to the regular excitations -- form isospin triplets, rather than singlets.

hep-ph↗

arXiv2017

Pion radiative weak decay from the instanton vacuum

We investigate the vector and axial-vector form factors for the pion radiative weak decays $π^+\to e^+ν_e γ$ and $π^+\to e^+ν_e e^+ e^-$, based on the gauged effective chiral action from the instanton vacuum in the large $N_c$ limit. The nonlocal contributions, which arise from the gauging of the action, enhance the vector form factor by about $20\,\%$, whereas the axial-vector form factor is reduced by almost $30\,\%$. Both the results for the vector and axial-vector form factors at the zero momentum transfer are in good agreement with the experimental data. The dependence of the form factors on the momentum transfer is also studied. The slope parameters are computed and compared with other works.

hep-ph↗

arXiv2017

Photoproduction of the scalar mesons $f_0(500)$ and $f_0(980)$ off the nucleon

We investigate photoproduction of the scalar mesona off the nucleon, using the effective Lagrangians and the Regge approach. We first study $f_0(980)$ photoproduction, replacing the Feynman propagator with the Regge ones for the $ρ$-meson exchange in the $t$-channel. The model parameters are fixed by reproducing the experimental data on the differential cross section. We then apply the same method to $f_0(500)$ or $σ$ photoproduction with the same parameters for the Regge propagator. Since the threshold energy of the $f_0(500)$ production is rather low, $N^*$ resonances, which can decay into the nucleon and two pions in the isoscalar and scalar state, can come into play in the $s$-channel. To examine the effects of the $N^*$ resonances, we set up two models to look into the respective contribution of the $N^*$ resonances. We find that in particular $N^*(1440)$ and $N^*(1680)$ play important roles in $f_0(500)$ photoproduction. We discuss the physical implications of the present results.

hep-ph↗

arXiv2017

Photoproduction of $Λ(1405)$ with the $N^*$ and $t$-channel Regge contributions

We investigate the photoproduction of $Λ(1405)\equivΛ^*$ hyperon resonance, i.e., $γp\to K^+Λ^*$, employing the effective Lagrangian approach with the $t$-channel Regge trajectories at tree level. We extensively explore the effects from the nucleon resonances in the vicinity of the threshold $\sqrt{s}_\mathrm{th}\approx1900$ MeV, i.e., $N(2000)$, $N(2030)$, $N(2055)$, $N(2095)$, and $N(2100)$, and observe that they are of great importance to reproduce the recent CLAS/Jlab experimental data. Total and differential cross sections are given as numerical results and compared with the experimental data, in addition to the $t$-channel momentum transfer and photon-beam asymmetry. The invariant-mass plots for $γp\to K^+π^0Σ^0$ via $Λ^*$ are also extracted from the two-body process results, showing a qualitative agreement with the data. We also discuss the constituent-counting rule for the internal structure of $Λ^*$, resulting in that $Λ^*$ appears to be different from a simple three-quark $(uds)$ state.

hep-ph↗

arXiv2017

Instanton effects on the heavy-quark static potential

We investigate the instanton effects on the heavy-quark potential,including its spin-dependent part, based on the instanton liquid model. Starting with the central potential derived from the instanton vacuum, we obtain the spin-dependent part of the heavy-quark potential. We discuss the results of the heavy-quark potential from the instanton vacuum. We finally solve the nonrelativistic two-body problem, associating with the heavy-quark potential from the instanton vacuum. The instanton effects on the quarkonia spectra are marginal but are required for quantitative description of the spectra.

hep-ph↗