Authors: N. Suzuki, T. Sato and T. -S. H. Lee
Title: Extraction of resonance parameters from meson production reactions
Keywords: nucleon resonance, transition form factor
Abstract:
The excited baryon and meson states couple strongly with the continuum
states and they are identified with the resonance states in hadron reactions. The spectra and decay widths of the hadron resonances reveal the role of the confinement and chiral symmetry of QCD in the non-perturbative region.
Therefore, the extraction of the basic resonance parameters from reaction data is one of the important tasks in hadron physics.
In this work we report on our recent progress on a method to extract the resonance parameters from meson production reactions[1] and the resonance parameters[2] obtained from the application of this method.
The resonances are characterized from the pole of the partial wave amplitude on the complex energy plane. For multi-channel case, the analytic structure
of the scattering T-matrix becomes non-trivial. We developed an analytic continuation method for extracting the resonance parameters within a recently developed Hamiltonian formulation of meson-nucleon reactions.
The method was tested for simple solvable models and then applied for the coupled channels ($\pi N$, $\eta N$, $\pi\Delta$, $\rho N$, and $\sigma N$ ) model of the $\pi N$ and $\gamma^* N$ reactions up to $W < 2GeV$[3-4].
The pole positions of the amplitudes give the resonance energies and the total width. Then the electromagnetic helicity amplitudes and the strong interaction decay vertex of the resonances are obtained form the residues of the amplitudes at resonance pole. We report on the N* parameter obtained from this method for some of the N* resonances. The comparison of our approach with the others such as K-matrix method and Breit-Wigner parametrization is discussed.
[1] N. Suzuki, T. Sato, T.-S. H. Lee, arXive:0806.2043[nucl-th]
[2] N. Suzuki, T. Sato, T.-S. H. Lee, in preparation
[3] A. Matsuyama, T. Sato and T.-S. H. Lee, Phys. Rep. 439 (2007) 193
[4] B. Julia-Diaz, T.-S. H. Lee, T. Sato and L.C. Smith, Phys.Rev.
C75(2007)015205
H. Kamano, B. Julia-Diaz, T. -S. H. Lee, A. Matsuyama, T. Sato,
arXiv:0807.2273[nucl-th] |