Strong decay of low-lying S 11 and D 13 nucleon resonances to pseudoscalar mesons and octet baryons

A chiral quark-model approach is adopted to study the γp → η ′ p and γn → η ′ n. Good descriptions of the recent observations from CLAS and CBELSA/TAPS are obtained. Both of the processes are governed by S 11 (1535) and u channel background. Strong evidence of an n = 3 shell resonance D 15 (2080) is found in the reactions, which accounts for the bump-like structure around W = 2.1 GeV observed in the total cross section and excitation functions at very forward angles. The S 11 (1920) seems to be needed in the reactions, with which the total cross section near threshold for the γp → η ′ p is improved slightly. The polarized beam asymmetries show some sensitivities to D 13 (1520), although its effects on the differential cross sections and total cross sections are negligible. There is no obvious evidence of the P-, D 13 -, F-and G-wave resonances with a mass around 2.0 GeV in the reactions.

Section: A Parameterssupporting

confidence: 75%

η′photoproduction on the nucleon in the quark model

Zhong

Zhao

2011

“…• Set II: ω 3 = 340 MeV and ω 5 = 600 MeV, values adopted to reproduce the data for electromagnetic and strong decays of several baryon resonances [34,35], corresponding to R ≃ 1.76 and C 35 ≃ 0.63.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

Strangeness magnetic form factor of the proton in the extended chiral quark model

Saghai

2013

Self Cite

Background: Unravelling the role played by nonvalence flavors in baryons is crucial in deepening our comprehension of QCD. The strange quark, a component of the higher Fock states in baryons, is an appropriate tool to study nonperturbative mechanisms due to the pure sea quark.Purpose: Study the magnitude and the sign of the strangeness magnetic moment µ s and the magnetic form factor (G s M ) of the proton. Methods:Within an extended chiral constituent quark model, we investigate contributions from all possible five-quark components to µ s and G s M (Q 2 ) in the four-vector momentum range Q 2 ≤ 1 (GeV/c) 2 . The probability of the strangeness component in the proton wave function is calculated employing the 3 P 0 model. Results:Predictions are obtained by using input parameters taken from the literature. The observables µ s and G s M (Q 2 ) are found to be small and negative, consistent with the lattice-QCD findings as well as with the latest data released by the PVA4 and HAPPEX Collaborations.Conclusions: Due to sizeable cancelations among different configurations contributing to the strangeness magnetic moment of the proton, it is indispensable to i) take into account all relevant five-quark components and include both diagonal and non-diagonal terms, ii) handle with care the oscillator harmonic parameter ω 5 and the ss component probability.

“…3, the numerical results are somewhat sensitive to R 35 in all three interaction models, the variation of the energies amount up to 160 MeV. The energies of the lowest states in the three models first decrease and then increase with increasing values for R 35 and lie within the range ∼ 1750 ± 50 MeV The energies of the other states just increase with R 35 , with the exception of the blue-dash-dotted lines in the OGE and GBE models, which represent the energy of the fourth five-quark configuration in these two models, which does not mix with any others states in the OGE and GBE models, so the energies of this state are independent of R 35 .…”

Section: B Dependence Of Numerical Results On Parametersmentioning

confidence: 92%

“…[34][35][36][37], in order to reproduce the electromagnetic and strong decays of nucleon resonances, both R 35 > 1 and R 35 < 1 have been suggested. In [34][35][36][37] it was shown that the most sensitive parameter is in fact the ratio 2ω 3 ω 5 /(ω 2 3 + ω 2 5 ). It is thus very difficult to judge whether R 35 is less than 1 or not.…”

Section: B Dependence Of Numerical Results On Parametersmentioning

confidence: 99%

Mixing of the low-lying three- and five-quarkΩstates with negative parity

Metsch

Zou

2013

Self Cite

Mixing of the low-lying three-and five-quark Ω states with spin-parity quantum numbers 1 2 − and 3 2 − is investigated, employing an instanton-induced quark-antiquark pair creation model, which precludes transitions between s 3 and s 4s configurations. Models with hyperfine interactions between quarks of three different kinds, namely, one-gluon-exchange, Goldstone-boson-exchange (GBE) and an instanton-induced interaction (INS) are called OGE, GBE and INS models, respectively. Numerical results show that the instanton-induced pair creation causes strong mixing between the threeand five-quark configurations with spin 3/2, and that this mixing decreases the energy of the lowest spin 3/2 states in all three different hyperfine interaction models to ∼ 1750 ± 50 MeV. On the other hand, transition couplings between s 3 and s 3 qq states with spin 1/2 caused by instanton-induced qq creation is very small and the resulting mixing of three-and five-quark configurations in the OGE and INS models is negligible, while the mixing of the spin 1/2 states in GBE model is not, but effects of this mixing on energies of mixed states are also very small. Accordingly, the lowest Ω states with negative parity in all three hyperfine interactions models have spin 3/2.