Excitation of S11 resonances in pion scattering and pion photoproduction on the proton

✍ Scribed by Guan-Yeu Chen; Sabit Kamalov; Shin Nan Yang; Dieter Drechsel; Lothar Tiator

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 234 KB
• Volume: 723
• Category: Article
• ISSN: 0375-9474
• DOI: 10.1016/s0375-9474(03)01453-2

✦ Synopsis

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 (Γ 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.