arXiv subjects

Guan Yeu Chen

Publications and source records attributed to Guan Yeu Chen.

3 recordsLinked to original sources

arXiv2007

Nucleon resonances in πN scattering up to energies \sqrt(s) < 2.0 GeV

A meson-exchange model for pion-nucleon scattering was previously constructed using a three-dimensional reduction scheme of the Bethe-Salpeter equation for a model Lagrangian involving π, η, N, Δ, ρ, and σfields. We thereby extend our previous work by including the ηN channel and all the πN resonances with masses ~ 2 GeV, up to the F waves. The effects of the ππN channels are taken into account by introducing an effective width in the resonance propagators. The extended model gives an excellent fit to both πN phase shifts and inelasticity parameters in all channels up to the F waves and for energies below 2 GeV. We present a new scheme to extract the properties of overlapping resonances. The predicted values for the resonance masses and widths as well as resonance pole positions and residues are compared to the listing of the Particle Data Group.

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arXiv2006

A meson-exchange piN model up to energies sqrt(s) < 2.0 GeV

A meson-exchange piN model, previously constructed using three-dimensional reduction scheme of the Bethe-Salpeter equation for a model Lagrangian involving π, η, N, Δ, rho, and σfields, is extended to energies up to 2 GeV by including the ηN channel and all the four stars πN resonances up to the F-waves. The effects of other 2 pion channels are taken into account phenomenologically. The extended model gives an excellent fit to both piN phase shifts and inelasticity parameters in all channels up to the F-waves. However, a few of the extracted resonance parameters differ considerably from the PDG values.

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arXiv2001

Recent developments in the dynamical and unitary isobar models for pion electromagnetic production

gamma N->Delta transition form factors and threshold pi^0 photo- and electroproduction are studied with the new version of MAID and a dynamical model. By re-analyzing the recent Jlab data on p(e,e'p) pi^0 at Q^2 = 2.8 and 4.0 (GeV/c)^2, we find that the hadronic helicity conservation is not yet observed in this region of Q^2. The extracted R_{EM}, starting from a small and negative value at the real photon point, actually exhibits a clear tendency to cross zero and change sign as Q^2 increases, while the absolute value of R_{SM} is strongly increasing. Our analysis indicates that A_{1/2} and S_{1/2}, but not A_{3/2}, starts exhibiting the pQCD scaling behavior at about Q^2 = 2.5 (GeV/c)^2. For the pi^0 photo- and electroproduction near threshold, results obtained within the dynamical model with the use of a meson-exchange pi N model for the final state interaction are in as good agreement with the data as ChPT.

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