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Hyun-Chul Kim

Publications and source records attributed to Hyun-Chul Kim.

At least 145 records · Page 8Linked to original sources
arXiv2011

Lambda(1405,1/2^-) photoproduction from the gamma p -> K^+ Lambda(1405) reaction

We investigate the photoproduction of Lambda(1405,1/2^-) = Lambda* off the proton target using the effective Lagrangian in the Born approximation. We observed that, depending on the choice of the K* N Lambda* coupling strength, the total cross section becomes 0.1 <~ sigma_Lambda* <~ 0.2 mu b near the threshold and starts to decrease beyond E_gamma ~ 1.6 GeV, and the angular dependence shows a mild enhancement in the forward direction. It turns out that the energy dependence of the total cross section is similar to that shown in the recent LEPS experiment. This suggests that the production mechanism of the Lambda* is dominated by the s-channel contribution.

hep-ph↗
arXiv2011

Spin structure of the pion from the instanton vacuum

We investigate the spin structure of the pion within the framework of the nonlocal chiral quark model from the instanton vacuum. We first evaluate the tensor form factors of the pion for the first and second moment (n=1,2) and compare it with the lattice data. Combining the tensor form factor of the pion with the electromagnetic one, we determine the impact-parameter dependent probability density of transversely polarized quarks inside the pion. It turns out that the present numerical results for the tensor form factor as well as those for the probability density are in good agreement with the lattice data. We also discuss the distortion of the spatial distribution of the quarks in the transverse plane inside the pion.

hep-ph↗
arXiv2011

Tensor properties of the nucleon

We report in the present talk recent results of the tensor properties of the nucleon within the framework of the chiral quark-soliton model. The tensor and anomalous tensor magnetic form factors are calculated for the momentum transfer up to $Q^{2}\leq1\,\mathrm{GeV}^{2}$ and at a renormalization scale of $0.36\,\mathrm{GeV}^{2}$. The main results are summarized as follows: the flavor tensor charges of the nucleon are yielded as $δu=1.08$, $δd=-0.31$, $δs=-0.01$, while the up and down anomalous tensor magnetic moments are evaluated as $κ_{T}^{u}=3.56$ and $κ_{T}^{d}=1.83$, respectively. The strange anomalous tensor magnetic moment turns out to be $κ_{T}^{s}=0.2\sim -0.2$, compatible with zero. We discuss their physical implications, comparing them in particular with those from the lattice QCD.

hep-ph↗
arXiv2011

Nucleon properties in nuclear matter

We present recent studies on the effective mass of the nucleon in infinite and homogeneous nuclear matter and its relation to nuclear matter properties within the framework of the in-medium modified Skyrme model. Medium modifications are achieved by introducing optical potential for pion fields and parametrization of the Skyrme parameter in nuclear medium. The present approach is phenomenologically well justified by pion physics in nuclear matter and describe successfully bulk nuclear matter properties.

nucl-th↗
arXiv2011

K*Λ(1116) photoproduction and nucleon resonances

In this presentation, we report our recent studies on the $K^*Λ(1116)$ photoproduction off the proton target, using the tree-level Born approximation, via the effective Lagrangian approach. In addition, we include the nine (three- or four-star confirmed) nucleon resonances below the threshold $\sqrt{s}_\mathrm{th}\approx2008$ MeV, to interpret the discrepancy between the experiment and previous theoretical studies, in the vicinity of the threshold region. From the numerical studies, we observe that the $S_{11}(1535)$ and $S_{11}(1650)$ play an important role for the cross-section enhancement near the $\sqrt{s}_\mathrm{th}$. It also turns out that, in order to reproduce the data, we have the vector coupling constants $g_{K^*S_{11}(1535)Λ}=(7.0\sim9.0)$ and $g_{K^*S_{11}(1650)Λ}=(5.0\sim6.0)$.

hep-ph↗
arXiv2011

Binding energy per nucleon and hadron properties in nuclear matter

We investigate the binding energy per nucleon and hadron properties in infinite and homogeneous nuclear matter within the framework of the in-medium modified Skyrme model. We first consider the medium modifications of the single hadron properties by introducing the optical potential for pion fields into the original Lagrangian of the Skyrme model. The parameters of the optical potential are well fitted to the low-energy phenomenology of pion-nucleus scattering. Furthermore, the Skyrme term is also modified in such a way that the model reproduces bulk properties of nuclear matter, in particular, the binding energy per nucleon. The present approach is self-consistent: the single hadron properties in a nuclear medium, their effective in-medium interactions, and the bulk matter properties are treated on the same footing.

hep-ph↗
arXiv2010

Electromagnetic mass differences of SU(3) baryons within a chiral soliton model

We investigate the electromagnetic mass differences of SU(3) baryons, using an "model-independent approach" within a chiral soliton model. The electromagnetic self-energy corrections to the masses of the baryon are expressed as the baryonic two-point correlation function of the electromagnetic currents. Using the fact that the electromagnetic current can be treated as an octet operator, and considering possible irreducible representations of the correlation function, we are able to construct a general collective operator for the electromagnetic self-energies, which consists of three unknown parameters. These parameters are fixed, the empirical data for the electromagnetic mass differences of the baryon octet being employed. We predict those of the baryon decuplet and antidecuplet. In addition, we obtain various mass relations between baryon masses within the corresponding representation with isospin symmetry breaking considered. We also predict the physical mass differences of the baryon decuplet. The results are in good agreement with the exisiting data.

hep-ph↗
arXiv2010

Anomalous tensor magnetic moments and form factors of the proton in the self-consistent chiral quark-soliton model

We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider $1/N_c$ rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: $κ_{T}^{u}=3.56$ and $κ_{T}^{d}=1.83$, respectively. The strange anomalous tensor magnetic moment is yielded to be $κ_{T}^{s}=0.2\sim -0.2$, that is compatible with zero. We also calculate the corresponding form factors $κ_{T}^{q}(Q^{2})$ up to a momentum transfer $Q^{2}\leq 1\,\mathrm{GeV}^{2}$ at a renormalization scale of $0.36\,\mathrm{GeV}^{2}$.

hep-ph↗
arXiv2010

Tensor charges and form factors of SU(3) baryons in the self-consistent SU(3) chiral quark-soliton model

We investigate the tensor form factors of the baryon octet within the framework of the chiral quark-soliton model, emphasizing those of the nucleon, taking linear 1/N_c rotational as well as linear m_s corrections into account, and applying the symmetry-conserving quantization. We explicitly calculate the tensor form factors H_{T}^{q}(Q^{2}) corresponding to the generalized parton distributions H_{T}(x,ξ,t). The tensor form factors are obtained for the momentum transfer up to Q^{2}\leq1\,\mathrm{GeV}^{2} and at a renormalization scale of 0.36\,\mathrm{GeV}^{2}. We find for the tensor charges δu=1.08, δd=-0.32, δs=-0.01 and discuss their physical consequences, comparing them with those from other models. Results for tensor charges for the baryon octet are also given.

hep-ph↗
arXiv2010

Mesons and nucleons from holographic QCD

We present in this talk a recent investigation on a unified approach within the framework of a hard-wall model of AdS/QCD. We first study a theoretical inconsistency in existing models. In order to remove this inconsistency, we propose a unified approach in which the mesons and the nucleons are treated on the same footing, the same infrared (IR) cutoff being employed in both fermionic and bosonic sectors. We also suggest a possible way of improving the model by introducing a five-dimensional anomalous dimension.

hep-ph↗
arXiv2009

Hadrons from a hard wall AdS/QCD model

We review a recent work on masses of mesons and nucleons within a hard wall model of holographic QCD in a unified approach. In order to treat meson and nucleon properties on the same footing, we introduced the same infrared (IR) cut for both sectors. In framework of present approach, the best fit to the experimental data is achieved introducing the anomalous dimension for baryons.

hep-ph↗
arXiv2009

Non-Fermi liquid from confinement in doped Mott insulators

A phenomenological description for confinement of fractionalized excitations is proposed in the gauge theory approach for doped Mott insulators. Introducing the Polyakov-loop parameter into an SU(2) gauge theory for the t-J model, we show that electron excitations emerge below the so-called coherence temperature, resulting from confinement of spinons and holons via the formation of the Polyakov loop. Remarkably, such confined electrons turn out to exhibit non-Fermi liquid physics without quantum criticality, yielding the electric resistivity in quantitative agreement with experimental data. The Higgs phase is not allowed due to confinement, suggesting a possible novel mechanism of superconductivity in the strong coupling approach.

cond-mat.str-el↗
arXiv2009

Mesons and nucleons from holographic QCD in a unified approach

We investigate masses and coupling constants of mesons and nucleons within a hard wall model of holographic QCD in a unified approach. We first examine an appropriate form of fermionic solutions by restricting the mass coupling for the five dimensional bulk fermions and bosons. We then derive approximated analytic solutions for the nucleons and the corresponding masses in a small mass coupling region. In order to treat meson and nucleon properties on the same footing, we introduce the same infrared (IR) cut in such a way that the meson-nucleon coupling constants, i.e., g_{pi NN} and g_{rho NN} are uniquely determined. The first order approximation with respect to a dimensionless expansion parameter, which is valid in the small mass coupling region, explicitly shows difficulties to avoid the IR scale problem of the hard wall model. We discuss possible ways of circumventing these problems.

hep-ph↗
arXiv2009

Photoproduction of the Theta^+ and its vector and axial-vector structure

We present recent investigations on the vector and axial-vector transitions of the baryon antidecuplet within the framework of the self-consistent SU(3) chiral quark-soliton model, taking into account the 1/N_c rotational and linear m_s corrections. The main contribution to the electric-like transition form factor comes from the wave-function corrections. This is a consequence of the generalized Ademollo-Gatto theorem. It is also found that in general the leading-order contributions are almost canceled by the rotational 1/N_c corrections. The results are summarized as follows: the vector and tensor K^*-N-Theta coupling constants, g_{K^*-N-Theta}=0.74 - 0.87 and f_{K^*-N-Theta}=0.53 - 1.16, respectively, and Gamma_{Theta->KN}=0.71 MeV, based on the result of the K-N-Theta coupling constant g_{K-n-Theta}=0.83. We also show the differential cross sections and beam asymmetries, based on the present results. We also discuss the connection of present results with the original work by Diakonov, Petrov, and Polyakov.

hep-ph↗
arXiv2009

Magnetic susceptibility of the QCD vacuum at finite quark-chemical potential

We investigate the QCD magnetic susceptibility chi at the finite quark-chemical potential (mu>0) and at zero temperature (T=0) to explore the pattern of the magnetic phase transition of the QCD vacuum. For this purpose, we employ the nonlocal chiral quark model derived from the instanton vacuum in the presence of the chemical potential in the chiral limit. Focusing on the Nambu-Goldstone phase, we find that the magnetic susceptibility remains almost stable to mu~200 MeV, and falls down drastically until the the quark-chemical potential reaches the critical point mu_c~320 MeV. Then, the strength of the chi is reduced to be about a half of that at mu=0, and the first-order magnetic phase transition takes place, corresponding to the chiral restoration. From these observations, we conclude that the response of the QCD vacuum becomes weak and unstable to the external electromagnetic field near the critical point, in comparison to that for vacuum. It is also shown that the breakdown of Lorentz invariance for the magnetic susceptibility, caused by the finite chemical potential, turns out to be small.

hep-ph↗
arXiv2009

eta photoproduction and N* resonances

We investigate the eta photoproduction using the effective Lagrangian approach at the tree level. We focus on the new nucleon resonance N*(1675), which was reported by the GRAAL, CB-ELSA and Tohoku LNS, testing its possible spin and parity states theoretically (J^P=1/2^+-,3/2^+-). In addition, we include six nucleon resonances, D_13(1520), S_11(1535), S_11(1650), D_15(1675), P_11(1710), P_13(1720) as well as the possible background contributions. We calculate various cross sections including beam asymmetries for the neutron and proton targets. We find noticeable isospin asymmetry in transition amplitudes for photon and neutron targets. This observation may indicate that the new resonance can be identified as a non-strangeness member of the baryon antidecuplet.

hep-ph↗
arXiv2009

Photoproduction of Theta^+(1540,1/2^+) reexamined with new theoretical information

We reinvestigate the photoproduction of the exotic pentaquark baryon Theta^+(1540,1/2^+) from the gamma N -> Kbar Theta^+ reaction process within the effective Lagrangian approach, taking into account new theoretical information on the K-N-Theta and K*-N-Theta coupling strengths from the chiral quark-soliton model (chiQSM). We also consider the crossing-symmetric hadronic form factor, satisfying the on-shell condition as well. Due to the sizable vector and tensor couplings for the vector kaon, g_{K* N Theta} and f_{K* N Theta}, which are almost the same with the vector coupling g_{K N Theta} ~ 0.8 for the pseudoscalar kaon, the K*-exchange contribution plays a critical role in the photon beam asymmetries.

hep-ph↗