Physics – Nuclear Physics – Nuclear Theory
Scientific paper
2002-10-05
Nucl.Phys. A723 (2003) 447-463
Physics
Nuclear Physics
Nuclear Theory
15 pages LATEX including 7 tables and 7 figures, revised version
Scientific paper
10.1016/S0375-9474(03)01453-2
A self-consistent analysis of pion scattering and pion photoproduction within a coupled channels dynamical model is presented. In the case of pion photoproduction, we obtain background contributions to the imaginary part of the S-wave multipole which differ considerably from the result based on the K-matrix approximation. Within the dynamical model these background contributions become large and negative in the region of the S_{11}(1535) resonance. Due to this fact much larger resonance contributions are required in order to explain the results of the recent multipole analyses. For the first S_{11}(1535) resonance we obtain as a value of the dressed electromagnetic helicity amplitude: A_{1/2}=(72 +/- 2) * 10^{-3} GeV^{-1/2}. Similar values can be derived from eta photoproduction if one takes the same total width Gamma_R=95 +/- 5 MeV) as in pion scattering and pion photoproduction. The combined analysis yields considerable strength at invariant mass W>1750 MeV, which can be explained by a third and a fourth S_{11} resonance with the masses 1846 +/- 47 and 2113 +/- 70 MeV.
Chen Guan-Yeu
Drechsel Dieter
Kamalov Sabit S.
Tiator Lothar
Yang Shin Nan
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