S11 resonances in pion scattering and pion photoproduction

por Sabit Kamalov (Mainz University and Dubna)

viernes 9 jul. 2004 15:00 → 16:00 Europe/Madrid

Sala Seminarios IFIC (Edf. Institutos de Investigación)

A self-consistent analysis of pion scattering and pion photoproduction within a coupled channels dynamical model is presented. The results indicate the existence of a third and a fourth $S_{11}$ resonance with the masses $1846\pm 47$ and $2113\pm 70$ MeV. 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 analysis. For the first $S_{11}(1535)$ resonance we obtain as a value of the electromagnetic helicity amplitude: $A_{1/2}=72\pm 2 \times 10^{-3}$GeV$^{-1/2}$.}