arXiv subjects
Publications and source records attributed to Klaus Goeke.
We propose a scenario in which Roper octet can mix with a putative antidecuplet of exotic baryons and predict the properties of its strange members. We show that 1795 MeV < M_Sigma_{\bar{10}} <1830 MeV and 1900 MeV < M_Xi_{\bar{10}}<1970 MeV. We also estimate total widths: 10 MeV < Gamma_Σ_{\bar{10}}< 30 MeV} and Gamma_Ξ_{\bar{10}}\sim 10 MeV and branching ratios for different decay modes.
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.
We investigate the semileptonic hyperon decays within the framework of the self-consistent SU(3) chiral quark-soliton model ($χ$QSM). We take linear $1/N_c$ rotational as well as linear $m_s$ corrections into account and apply the symmetry conserving quantization. We present the results for the form factors $f_1(Q^2)$, $f_2(Q^2)$ and $g_1(Q^2)$ in addition to the semileptonic decay constants of hyperons. We also have calculated the radii and dipole masses of these form factors for all relevant strangeness-conserving and strangeness-changing transitions.
We investigate the axial-vector transition constants of the baryon antidecuplet to the octet and decuplet within the framework of the self-consistent SU(3) chiral quark-soliton model. Taking into account rotational 1/N_c and linear m_s corrections and using the symmetry-conserving quantization, we calculate the axial-vector transition constants. It is found that the leading-order contributions are generally almost canceled by the rotational 1/N_c corrections. Thus, the m_s corrections turn out to be essential contributions to the axial-vector constants. The decay width of the Theta^+ to NK transition is determined to be Gamma(Theta -> NK)=0.71, MeV, based on the result of the axial-vector transition constant g_A^* (Theta -> NK)=0.05. In addition, other strong decays of the baryon antidecuplet are investigated.
We present in this talk recent results of the vector and axial-vector transitions of the nucleon to the pentaquark baryon Theta^{+}, based on the SU(3) chiral quark-soliton model. The results are summarized as follows: K^{*}-N-Theta vector and tensor coupling constants turn out to be g_{K^{*}N Theta} = 0.81 and f_{K^{*}N Theta}=0.84, respectively, and the KN Theta axial-vector coupling constant to be g_{A}^* = 0.05. As a result, the total decay width for Theta^+ to NK becomes very small: Gamma_{Theta -> NK} = 0.71 MeV, which is consistent with the DIANA result Gamma_{Theta -> NK}=0.36 +- 0.11 MeV.
We investigate the vector transition form factors of the nucleon and vector meson K^* to the pentaquark baryon Theta^+ within the framework of the SU(3) chiral quark-soliton model. We take into account the rotational 1/N_c and linear $m_{\rm s}$ corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. It turns out that the leading-order contributions to the form factors are almost cancelled by the rotational corrections. Because of this, the flavor SU(3) symmetry-breaking terms yield sizeable effects on the vector transition form factors. In particular, the main contribution to the electric-like transition form factor comes from the wave-function corrections, which is a consequence of the generalized Ademollo-Gatto theorem derived in the present work. We estimate with the help of the vector meson dominance the K^* vector and tensor coupling constants for the Theta^+: $g_{K^{*}NΘ}=0.74 - 0.87$ and $f_{K^{*}NΘ}=0.53 - 1.16$. We argue that the outcome of the present work is consistent with the null results of the CLAS experiments in the reactions gamma n -> K^- Theta^+ and gamma p ->bar{K}^0 Theta^+. The results of the present work are also consistent with the recent experiments at KEK. In addition, we present the results of the $Σ_{\bar{10}}\to N\bar{K}^*$ transition form factors and its $\bar{K}^*NΣ_{\bar{10}}$ coupling constants.
We investigate the magnetic susceptibility of the QCD vacuum with the $1/N_c$ corrections taken into account, based on the instanton vacuum. Starting from the instanton liquid model we derive the gauged light-quark partition function in the presence of the current quark mass as well as of external Abelian vector and tensor fields. We consider the $1/N_c$ meson-loop corrections which are shown to contribute to the magnetic susceptibility by around 15% for the up (and down) quarks. We also take into account the tensor terms of the quark-quark interaction from the instanton vacuum as well as the finite-width effects, both of which are of order $\mathcal{O}(1/N_c)$. The effects of the tensor terms and finite width turn out to be negligibly small. The final results for the up-quarks are given as: $χ< iψ^\dagger ψ>_0 \simeq 35-40 \mathrm{MeV}$ with the quark condensate $ _0$. We also discuss the pion mass dependence of the magnetic susceptibility in order to give a qualitative guideline for the chiral extrapolation of lattice data.
We use the chiral quark soliton model to estimate masses and widths of the two eikosiheptaplets (27-plets of SU(3) flavor) of spin 3/2 and 1/2 that emerge in the rigid rotator quantization. We use as input: hyperon decays, Theta+ mass and width. While 27_{3/2} has small widths (although much larger than the values allowed by the partial wave analysis), 27_{1/2} has large decay widths to antidecuplet. However exactly for this decay channels the widths are suppressed in the large N_{c} limit.
Using the exisiting experimental data for hyperon semileptonic decays and the flavor-singlet axial-vector charge $g_{A}^{(0)}$ from polarized deep inelastic scattering of the proton, we derive the decay width of the $Θ^{+}$ pentaquark baryon. We take into account the effects of flavor SU(3) symmetry breaking within the framework of the chiral quark-soliton model. All dynamical parameters of the model are fixed by using the five experimental hyperon semileptonic decay constants and flavor singlet axial-vector charge. We obtain the numerical results of the decay width of the $Θ^{+}$ pentaquark baryon as a function of the pion-nucleon sigma term $Σ_{πN}$ and investigate the dependence of the decay width of the $Θ^{+}$ on the $g_{A}^{(0)}$, varying the $g_{A}^{(0)}$ within the range of the experimental uncertainty. We demonstrate that the combined values of all known semileptonic decays with the generally accepted value of $g_{A}^{(0)} \approx 0.3$ for the proton are compatible with a small decay width $Γ_{ΘKN}$ of the $Θ^{+}$ pentaquark, i.e. $Γ_{ΘKN} \leq 1$ MeV.
We study the cross section for one-particle inclusive deep inelastic scattering off the nucleon for low transverse momentum of the detected hadron. We decompose the cross section in terms of structure functions and calculate them at tree level in terms of transverse-momentum-dependent parton distribution and fragmentation functions. Our results are complete in the one-photon exchange approximation at leading and first subleading twist accuracy, with both beam and target polarization.
We summarize the results of the chiral quark-soliton model ($χ$QSM) concerning basically all form factors necessary to interpret the present data of the parity violating electron scattering experiments SAMPLE, HAPPEX, A4 and G0. The results particularly focus on the recently measured asymmetries and the detailed data for various combinations of $G_{M}^{s}$, $G_{E}^{s}$, $\tilde{G}_{A}^{p}$ and $\tilde{G}_{A}^{n}$ at $Q^2=0.1$ GeV$^2$. The calculations yield positive strange magnetic and electric form factors and a negative axial vector one, all being rather small. The results are very close to the combined experimental world data from parity violating electron scattering and elastic $νp$- and $\bar{νp}$- scattering.
We investigate the electric form factors and charge radii of the pentaquark baryons within the framework of the chiral quark-soliton model. We consider the rotational $1/N_c$ and linear $m_s$ corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. The flavor-decomposed charge densities of the $Θ^+$ are presented. The electric form factors and charge radii of the charged pentaquark baryons turn out to be very similar to those of the corresponding octet baryons. The charge radii of the neutral pentaquark baryons are obtained to be very tiny and positive. The strange electric form factor of the pentaquark proton is shown to be larger than the corresponding one of the proton by around 20%. We also present the charge radii of the baryon decuplet for comparison.
We investigate parity-violating electroweak asymmetries in the elastic scattering of polarized electrons off protons within the framework of the chiral quark-soliton model ($χ$QSM). We use as input the former results of the electromagnetic and strange form factors and newly calculated SU(3) axial-vector form factors, all evaluated with the same set of four parameters adjusted several years ago to general mesonic and baryonic properties. Based on this scheme, which yields positive electric and magnetic strange form factors with a $μ_s=(0.08-0.13)μ_N$, we determine the parity-violating asymmetries of elastic polarized electron-proton scattering. The results are in a good agreement with the data of the A4, HAPPEX, and SAMPLE experiments and reproduce the full $Q^2$-range of the G0-data. We also predict the parity-violating asymmetries for the backward G0 experiment.
We investigate three different axial-vector form factors of the nucleon, $G_A^{0}$, $G_A^3$, $G_A^8$, within the framework of the SU(3) chiral quark-soliton model, emphasizing their strangeness content. We take into account the rotational $1/N_c$ and linear strange quark ($m_s$) contributions using the symmetry-conserving SU(3) quantization and assuming isospin symmetry. The strange axial-vector form factor is also obtained and they all are discussed in the context of the parity-violating scattering of polarized electrons off the nucleon and its relevance to the strange vector form factors.
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.
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.
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.
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.