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Hyun-Chul Kim

Publications and source records attributed to Hyun-Chul Kim.

At least 217 records · Page 12Linked to original sources
arXiv2001

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

The strange properties of the nucleon are investigated within the framework of the SU(3) chiral quark-soliton model assuming isospin symmetry and applying the symmetry conserving SU(3) quantization. We present the form factors $G^0_{E,M}(Q^2)$, $G^Z_M(Q^2)$ and the electric and magnetic strange form factors $G^s_{E,M}(Q^2)$ incorporating pion and kaon asymptotics. The results show a fairly good agreement with the recent experimental data from the SAMPLE and HAPPEX collaborations. We also present predictions for future measurements including the A4 experiment at MAMI (Mainz).

hep-ph↗
arXiv2001

$ΔS=1,2$ Effective Weak Chiral Lagrangian from the Instanton Vacuum

We study the effective weak chiral Lagrangian within the framework of the instanton vacuum. We incorporate the $ΔS=1,2$ effective weak Hamiltonian into the effective low-energy QCD partition function defining the chiral symmetric quark-Goldstone boson interactions with the momentum-dependent dynamical quark mass. Employing the derivative expansion, we derive the corresponding weak effective Lagrangian in leading order with the low energy constants to be used e.g. in chiral perturbation theory. We find that the momentum-dependent dynamical quark mass plays an essential role in improving the low energy constants and their ratio $g_{8}/g_{27}$.

hep-ph↗
arXiv2000

Spin structure of the octet baryons

We analyze the semileptonic weak decays of the octet baryons in a "{\em model independent}" approach, based on the algebraic structure of the Chiral Quark-Soliton Model. We argue that this analysis is in fact more general than the model itself. While the symmetry breaking for the semileptonic decays themselves is not strong, other quantities like $Δs$ and $ΔΣ$ are much more affected. We calculate $ΔΣ$ and $Δq$ for all octet baryons. Unfortunately, large experimental errors of $Ξ^-$ decays propagate in our analysis, in particular, in the case of $ΔΣ$ and $Δs$. Only if the errors for these decays are reduced, the accurate theoretical predictions for $ΔΣ$ and $Δs$ will be possible.

hep-ph↗
arXiv2000

Spin content of the $Λ$ hyperon

Using the known experimental data for the hyperon semileptonic decay constants, we calculate integrated quark densities $Δq_Λ$ and $% ΔΣ_Λ$ for the hyperon $Λ$ with flavor SU(3) symmetry breaking taken into account. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by the experimental data for six hyperon semileptonic decay constants. This parametrization allows us to reproduce the first moment of the $g_1^{\rm p}(x)$ of the proton. For the $Λ$ we obtain: $Δu_Λ=Δd_Λ \approx 0$ and $Δs_Λ$ of the order of 1. Unfortunately large experimental errors of $Ξ^-$ decays propagate in our analysis especially in the case of $ΔΣ_Λ$ and $Δs_Λ$. Only if the errors for these decays are reduced, the accurate theoretical predictions for $ΔΣ_Λ$ and $% Δs_Λ$ will be possible.

hep-ph↗
arXiv2000

Hyperon semileptonic decays and quark spin content of the proton

We investigate the hyperon semileptonic decays and the quark spin content of the proton $ΔΣ$ taking into account flavor SU(3) symmetry breaking. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by the experimental data for six hyperon semileptonic decay constants. As a result we predict the unmeasured decay constants, particularly for $Ξ^0 \to Σ^+$, which will be soon measured and examine the effect of the SU(3) symmetry breaking on the spin content $ΔΣ$ of the proton. Unfortunately large experimental errors of $Ξ^-$ decays propagate in our analysis making $ΔΣ$ and $Δs$ practically undetermined. We conclude that statements concerning the values of these two quantities, which are based on the exact SU(3) symmetry, are premature. We stress that the meaningful results can be obtained only if the experimental errors for the $Ξ$ decays are reduced.

hep-ph↗
arXiv1999

Effective Weak Chiral Lagrangian to ${\cal O} (p^4)$ in the Chiral Quark Model

We investigate the $ΔS = 1,2$ effective weak chiral Lagrangian within the framework of the chiral quark model. Starting from the effective four-quark operators, we derive the effective weak chiral action by integrating out the constituent quark fields. Employing the derivative expansion, we obtain the effective weak chiral Lagrangian to order ${\cal O} (p^4)$. We examine the contributions of the order ${\cal O} (N_c)$ to the ratio $g_{\underline{8}}/g_{\underline{27}}$, considering e.g. the quark axial-vector constant $g_{\rm A}$ different from unity. The low energy constants of the counterterms are also presented and discussed.

hep-ph↗
arXiv1999

Effective Weak Chiral Lagrangian from the Instanton Vacuum

We present in this talk the recent investigation of the effective weak chiral Lagrangian within the framework of the instanton-induced chiral quark model. The low energy constants in leading order $g_8$ and $g_{27}$, and their ratio are determined. The momentum-dependence of the constituent quark mass turns out to improve the low energy constants to the great extent, respecting the $ΔT=1/2$ enhancement.

hep-ph↗
arXiv1998

Effective $ΔS=1$ weak chiral Lagrangian from the instanton-induced chiral quark model

We present the recent investigation of the $ΔS = 1$ effective weak chiral Lagrangian within the framework of the instanton-induced chiral quark model. Starting from the effective four-quark operators, we derive the effective weak chiral action by integrating out the constituent quark fields. Employing the derivative expansion, we obtain the effective weak chiral Lagrangian to ${\cal O} (p^4)$ order with low energy constants.

hep-ph↗
arXiv1998

Flavor structure of the octet magnetic moments

We use the chiral quark-soliton model to identify all symmetry breaking terms linear in $m_{s}$ and investigate the strange magnetic moment in a ``model-independent'' way. Assuming hedgehog symmetry and employing the collective quantization, we obtain the most general expression for the flavor-singlet and flavor-octet magnetic moments in terms of seven independent parameters. Having fitted these parameters to the experimental magnetic moments of the octet baryons, we show that the strange magnetic moment turns out to be positive. The best fit obtained by minimizing $χ^2$ assuming 15% theoretical accuracy yields: $μ^{({\rm s})}_{N} = (0.41 \pm 0.18) μ_{N}$.

hep-ph↗
arXiv1998

Tensor susceptibilities of the vacuum from constituent quarks

We show that the constituent quark model leads to simple expressions for the isoscalar and isovector tensor susceptibilities of the vacuum. The found values are negative and of magnitude compatible with QCD-sum-rule parameterizations of spectral densities in appropriate L=1-meson channels.

hep-ph↗
arXiv1997

Magnetic moments of the SU(3) decuplet baryons in the chiral quark-soliton model

Magnetic moments of baryons are studied within the chiral quark soliton model with special emphasis on the decuplet of baryons. The model is used to identify all symmetry breaking terms proportional to $m_{\rm s}$. Sum rules for the magnetic moments are derived. A ``model-independent'' analysis of the symmetry breaking terms is performed and finally model calculations are presented, which show the importance of the rotational $1/N_{\rm c}$ corrections for cranking of the soliton.

hep-ph↗
arXiv1997

Semileptonic decay constants of octet baryons in the chiral quark-soliton model

Based on the recent study of the magnetic moments and axial constants within the framework of the chiral quark-soliton model, we investigate the baryon semileptonic decay constants $(f_1,f_2)$ and $(g_1, g_2)$. Employing the relations between the diagonal transition matrix elements and off-diagonal ones in the vector and axial-vector channels, we obtain the ratios of baryon semileptonic decay constants $f_2/f_1$ and $g_1/f_1$. The $F/D$ ratio is also discussed and found that the value predicted by the present model naturally lies between that of the Skyrme model and that of the nonrelativistic quark model. The singlet axial constant $g^{(0)}_A$ can be expressed in terms of the $F/D$ ratio and $g^{(3)}_A$ in the present model and turns out to be small. The results are compared with available experimental data and found to be in good agreement with them. In addition, the induced pseudotensor coupling constants $g_2/f_1$ are calculated, the SU(3) symmetry breaking being considered. The results indicate that the effect of SU(3) symmetry breaking might play an important role for some decay modes in hyperon semileptonic decay.

hep-ph↗
arXiv1997

The effects of the kaonic cloud on the neutron electric form factor

We investigate the effects of mesonic clouds on neutron electric and nucleon strange form factors in the framework of the chiral quark soliton model. We present a mechanism to identify the mesonic clouds and their Yukawa tail in the polarized Dirac sea. We find that, assuming hedgehog structures and semiclassical quantization, the neutron electric and the nucleon strange form factors are noticeably dependent on the value of the mass parameter in the Yukawa tails. A method is described to treat these Yukawa tails correctly. A hybrid way of calculating the neutron electric form factor is presented, which gives operationally both meson fields the proper Yukawa tails. This yields noticeably better agreement with experiment than previous calculations in the chiral quark soliton model and turns out to reproduce the data well.

hep-ph↗
arXiv1997

Weak electricity of the Nucleon in the Chiral Quark-Soliton Model

The induced pseudotensor constant (weak electricity) of the nucleon is calculated in the framework of the chiral quark soliton model. This quantity originates from the G-parity violation and hence is proportional to $m_u-m_d$. We obtain for $m_u-m_d=-5 MeV$ a value of $g_T/g_A =-0.0038$.

hep-ph↗
arXiv1996

Form factors of the nucleon in the SU(3) chiral quark-soliton model

The recent investigation on various form factors of the nucleon is reviewed in the framework of the SU(3) chiral quark-soliton model. The results for the electromagnetic and scalar form factors are in remarkable agreement with experimental and empirical data. The strange vector form factors are also discussed with the effect of the kaon cloud being considered. In addition to the form factors, the recent calculation of the tensor charges is presented.

hep-ph↗
arXiv1996

Tensor Charges of the Nucleon in the SU(3) Chiral Quark Soliton Model

The tensor charges of the nucleon are calculated in the framework of the SU(3) chiral quark soliton model. The rotational $1/N_c$ and strange quark mass corrections are taken into account up to linear order. We obtain the following numerical values of the tensor charges: $δu=1.12$, $δd=-0.42$, and $δs=-0.008$. In contrast to the axial charges, the tensor charges in our model are closer to those of the nonrelativistic quark model, in particular, the net number of the transversely polarized strange quarks in a transversely polarized nucleon $δs$ is compatible with zero.

hep-ph↗