arXiv subjects

Hyun-Chul Kim

Publications and source records attributed to Hyun-Chul Kim.

At least 199 records · Page 11Linked to original sources

arXiv2005

Exotic and nonexotic magnetic transitions in the context of the SELEX and GRAAL experiments

We calculate magnetic transition moments in the chiral quark-soliton model, with explicit SU(3)-symmetry breaking taken into account. The dynamical model parameters are fixed by experimental data for the magnetic moments of the baryon octet and from the recent measurements of $Θ^{+}$ mass. Known magnetic transition moments $μ_{ΛΣ}$, $μ_{NΔ}$ are reproduced and predictions for other octet-decuplet and octet-antidecuplet transitions are given. In particular $μ_{ΣΣ^{\ast}}$ recently constrained by SELEX is shown to be below $0.82 μ_N$. The recent GRAAL data on $η$ photoproduction off the nucleon are explained in terms of a new narrow antidecuplet neutron-like resonance.

hep-ph↗

arXiv2005

Production of Lambda(1520)

We investigate the Lambda(1520) photoproduction via the reaction process, gamma N -> K Lambda(1520). We employ the Born approximation and the Rarita Schwinger formalism is used for Lambda(1520). We reproduce the total cross sections and the various angular distributions qualitatively well for the proton target and estimate them for the neutron one. We find that the contact term contributes much more to the process than the other kinematical channels. Taking into account this fact, we reanalyze the K^*--exchange dominance hypothesis suggested by the previous experiments.

hep-ph↗

arXiv2005

Pentaquark $Θ^+$ mass and width in dense matter

We investigate medium modifications of the pentaquark $Θ^+$ in dense medium, taking into account different parities of the exotic $Θ^+$ baryon. We find that the chemical potential of the $Θ^+$ is shifted in a density-dependent way to one-loop order. We also investigated the effect of the scaled nucleon mass in dense medium on the $Θ^+$ propagator. The results turn out to depend sensitively on the scaled nucleon mass and on the parity of the $Θ^+$.

hep-ph↗

arXiv2005

Photoproduction of Lambda(1520,3/2^-)

We investigate the photoproduction of Lambda(1520,3/2^-) via the gamma N -> K Lambda^* reaction using the Born approximation and the Rariata-Schwinger vector-spinor field for the spin 3/2 particle. We reproduce the experimental data of the total cross section and the angular dependence for the proton target qualitatively well and estimate them for the neutron target. For the neutron target, we find much smaller total cross section than that of the proton and the significant K^*-exchange contribution.

hep-ph↗

arXiv2005

Determination of the parity of the pentaquark baryons : Theta^+ and Xi_5

We study determination of the parity of the pentaquark baryons in two different processes. First, we investigate the Theta^+ production via the vec{p} vec{p} -> Sigma^+ Theta^+ reaction process which was proposed to determine unambiguously the parity of Theta^+. We observe the clear differences in the total cross sections and the spin observable A_{xx}. As for the Xi_5 in the bar{K} N -> K Xi_5 reaction process, the total cross section for the positive parity presents about one hundred times lager than that of the negative one due to the huge destructive interference.

hep-ph↗

arXiv2005

Magnetic moments of exotic pentaquark baryons

In this talk, we present our recent investigation on the magnetic moments of the exotic pentaquark states, based on the chiral quark-soliton model, all relevant intrinsic parameters being fixed by using empirical data.

hep-ph↗

arXiv2004

Magnetic moments of the pentaquarks

We present in this talk a recent analysis for the magnetic moments of the baryon antidecuplet within the framework of the chiral quark-soliton model with linear $m_s$ corrections considered. We take into account the mixing of higher representations to the collective magnetic moment operator, which comes from the SU(3) symmetry breaking. Dynamical parameters of the model are fixed by experimental data for the magnetic moments of the baryon octet as well as by the masses of the octet, decuplet and of $Θ^{+}$. The magnetic moment of $Θ^{+}$ is rather sensitive to the pion-nucleon sigma term and ranges from $-1.19 {\rm n.m.}$ to $-0.33 {\rm n.m.}$ as the sigma term is varied from $Σ_{πN} = 45$ to 75 MeV, respectively. On top of them, we obtained that the strange magnetic moment of the nucleon has the value of $μ^{(s)}_N =+0.39$ n.m. within this scheme and turns out to be almost independent of the sigma term.

hep-ph↗

arXiv2004

Strange and singlet form factors of the nucleon: Predictions for G0, A4, and HAPPEX-II experiments

We investigate the strange and flavor-singlet electric and magnetic form factors of the nucleon within the framework of the SU(3) chiral quark-soliton model. Isospin symmetry is assumed and the symmetry-conserving SU(3) quantization is employed, rotational and strange quark mass corrections being included. For the experiments G0, A4, and HAPPEX-II we predict the quantities $G^{0}_E + βG^{0}_M$ and $G^{\rm s}_E + βG^{\rm s}_M$. The dependence of the results on the parameters of the model and the treatment of the Yukawa asymptotic behavior of the soliton are investigated.

hep-ph↗

arXiv2004

Theta^+ baryon production from gamma N and NN scattering

We investigate Theta^+ production via gamma N and NN reactions in order to obtain information on the structure of Theta^+, especially its parity. We observe that the positive parity. Theta^+production provides about ten times total cross sections than those of the negative parity one in both photon and nucleon induced reactions due to P-wave enhancement of the KNTheta vertex. We also consider the model independent method in the nucleon induced reaction to determine the parity of Theta^+ and show clearly distinguishable signals for the two parities.

nucl-th↗

arXiv2004

Photon and nucleon induced production of Theta^+

We investigate Theta^+ production via photon and nucleon induced reactions. We observe that the positive parity Theta^+ production provides about ten times larger total cross sections than those of the negative parity one in both photon and nucleon induced reactions due to P-wave enhancement of the K-N-Theta vertex. We also consider the model independent method in the nucleon induced reaction to determine the parity of Theta^+ and show clearly distinguishable signals for the two parities.

nucl-th↗

arXiv2004

Pentaquarks: Review on Models and Solitonic Calculations of Antidecuplet Magnetic Moments

After a quick look at the present status of experiments we shortly review in a first step the ongoing discussions on some of the basic theoretical approaches to pentaquarks: Chiral solitons, Large-$N_c$ considerations, quark models, and lattice gauge approaches. In a second step we apply the chiral quark-soliton approach including linear $m_s$-corrections to the calculation of magnetic moments of the baryons of the anti-decuplet. In this approach the parameters are fixed solely by experimental data for the magnetic moments of the baryon octet and for the masses of the octet, decuplet and of $Θ^{+}$. The magnetic moment of $Θ^{+}$ depends rather strongly on the pion-nucleon sigma term and reads $-1.19 {\rm n.m.}$ to $-0.33 {\rm n.m.}$ for $Σ_{πN} = 45$ and 75 MeV respectively. As a byproduct the strange magnetic moment of the nucleon is obtained with a value of $μ^{(s)}_N =+0.39$ n.m.

hep-ph↗

arXiv2004

Magnetic susceptibility of the QCD vacuum

We investigate the magnetic susceptibility of the QCD vacuum, based on the instanton vacuum. Starting from the instanton liquid model for the instanton vacuum, we derive the light-quark partition function $Z[V,T,\hat{m}]$ in the presence of the current quark mass $\hat{m}$ as well as the external Abelian vector and tensor fields. We calculate a two-point correlation function relevant for the magnetic susceptibility and derive it beyond the chiral limit. We obtain for the different flavors the following magnetic susceptibility: $χ_{u,d}< iψ_{u,d}^\dagger ψ_{u,d}>_0 \sim 40\sim45 {\rm MeV}$, while $χ_{s}< iψ_s^\dagger ψ_s >_0 \simeq 6\sim 10 {\rm MeV}$ with the quark condensate $ _0$.

hep-ph↗

arXiv2004

Octet, decuplet and antidecuplet magnetic moments in the chiral quark soliton model revisited

We reanalyse the magnetic moments of the baryon octet, decuplet, and antidecuplet within the framework of the chiral quark-soliton model, with SU(3) symmetry breaking taken into account. We consider the contributions of the mixing of higher representations to the magnetic moment operator arising from the SU(3) symmetry breaking. Dynamical parameters of the model are fixed by experimental data for the magnetic moments of the baryon octet and from the masses of the octet, decuplet and of $Θ^{+}$. The magnetic moment of $Θ^{+}$ depends rather strongly on the pion-nucleon sigma term and reads $-1.19 {\rm n.m.}$ to $-0.33 {\rm n.m.}$ for $Σ_{πN} = 45$ and 75 MeV respectively. The recently reported mass of $Ξ^{--}_{\bar{10}}(1862)$ is compatible with $Σ_{πN} = 73$ MeV. As a byproduct the strange magnetic moment of the nucleon is obtained with a value of $μ^{(s)}_N =+0.39$ n.m.

hep-ph↗

arXiv2004

Photo-production of the pentaquark $Θ^{+}$ with positive and negative parities

We investigate the production of the pentaquark $Θ^+$ baryon via the $γn\to K^-Θ^+$ and $γp\to \bar{K}^0 Θ^+$ processes, focusing on the parity of the $Θ^+$. Using the effective Lagrangians, we calculate the total and differential cross sections with the spin of the $Θ^+$ presumed to be 1/2. We employ the coupling constant of the $KNΘ$ vertex determined by assuming its mass and the decay width to be $1540 {\rm MeV}$ and $15 {\rm MeV}$. That of the $K^*NΘ$ is taken to be about a half of the $KNΘ$ coupling constant. We estimate the cutoff parameter by reproducing the total cross section of the $γp \to K^+ Λ$ reaction. It turns out that the total cross section for the $γn\to K^- Θ^+$ process is about four times larger than that of the $γp\to\bar{K}^0Θ^+$. We also find that the cross sections for the production of the positive-parity $Θ$ are about ten times as large as those for the negative-parity ones.

hep-ph↗

arXiv2003

Magnetic moments of exotic pentaquarks in the chiral quark-soliton model

We investigate the magnetic moments of the baryon antidecuplet within the framework of the chiral quark-soliton model in the chiral limit in a ``\emph{model-independent}'' approach. Sum rules for the magnetic moments are derived. The magnetic moment of $Θ^{+}$ is found to be about $0.2\sim 0.3 μ_{N}$.

hep-ph↗

arXiv2003

Effective chiral lagrangian in the chiral limit from the instanton vacuum

We study the effective chiral Lagrangian in the chiral limit from the instanton vacuum. Starting from the nonlocal effective chiral action, we derive the effective chiral Lagrangian, using the derivative expansion to order $O(p^4)$ in the chiral limit. The low energy constants, $L_1$, $L_2$, and $L_3$ are determined and compared with various models and the corresponding empirical data. The results are in a good agreement with the data. We also discuss about the upper limit of the sigma meson, based on the present results.

hep-ph↗

arXiv2003

A test of the instanton vacuum with low-energy theorems of the axial anomaly

We revisit the QCD+QED axial anomaly low-energy theorems which give an exact relation between the matrix elements of the gluon and photon parts of the axial anomaly operator equation within the framework of the {\em effective action} derived from the instanton vacuum. The matrix elements between the vacuum and two photon states and between the vacuum and two gluon states are investigated for arbitrary $N_f $ in the chiral limit. Having gauged the effective action properly, we show that the model does exactly satisfy the low-energy theorems.

hep-ph↗

arXiv2002

Strange vector form factors in the context of the SAMPLE, A4, HAPPEX and G0 experiments

We present the recent results of the strange vector form factors of the nucleon within the framework of the SU(3) chiral quark-soliton model. We compare our results with the recent experimental data of the SAMPLE and HAPPEX collaborations and find that they are in a good agreement with the data. We also predict the future experiments of the A4, HAPPEX-II and G0 collaborations.

hep-ph↗