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Nucleon Resonances in Scattering up to energies W < 2.0 GeV introduction a meson-exchange model for scattering conventional resonance parameters pole positions and residues summary and outlook G.Y. Chen, S.S. Kamalov, S.N. Yang, D. Drechsel and L.T. NTU Taipei, JINR Dubna, Universität Mainz
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dynamical meson exchange models for pion-nucleon scattering have been developed over many years, mostly in the energy region of the resonance the first goal is to extract N* parameters to investigate the structure of QCD and to compare with lattice calculations an open question is still: How can we understand the very successfull description of N* properties by constituent quark models and why does it fail in some other cases Dynamical Models
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another important point is the dynamical amplitude (formerly called off-shell amplitude), which plays a significant role in electromagnetic reactions, like loop effects in pion photoproduction within the dynamical models one can calculate the pion-loop contributions for threshold photo- and electroproduction in a similar way as in ChPT, but unrestricted in energy and momentum Dynamical Models
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previous work on Taipei meson exchange model:
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recent work on dynamical models for W<2 GeV: Mainz-Dubna-Taipei: Chen, Kamalov, Yang, Drechsel, L.T., nucl-th/0703096 with nucleon resonance analysis (this presentation) EBAC (JLab): Diaz, Lee, Matsuyama, Sato, nucl-th/0704.1615 with first step of a bigger project
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results of the fits to the SAID partial waves S waves single-energy pw analysis from SAID nonresonant background
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P waves
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D and F waves we find no improvement including F 17 (1990)
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Extraction of resonance parameters
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bare and physical resonance masses, total widths, branching ratios and background phases for N* resonances (I=1/2) bare phys our analysis PDG
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our analysis PDG bare mass physical mass additional res.
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resonance parameters for resonances (I=3/2) bare mass physical mass our analysis PDG
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resonance parameters for resonances (I=3/2) bare mass physical mass our analysis PDG additional res.
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pole positions and residues for N* resonances (I=1/2)
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pole positions and residues for resonances (I=3/2)
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a new meson-exchange model has been presented for pion nucleon scattering that fits the S,P,D,F waves very well up to W = 2.3 GeV for all but one PDG resonances below 2200 we can determine conventional resonance parameters and pole positions we cannot find the F 17 (1990) resonance (same as SAID), but find 4 broad states that are not listed in PDG: S 11 (1878), D 13 (2152), P 13 (2204), P 13 (2204) this model is very well suited for an application of pion and eta photo- and electroproduction Summary and Conclusions
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