Untersuchung der ersten Nukleonresonanzen in der Pion-Nukleon Streuung

In the present work we study the first excited states of the nucleon by investigating #pi#N scattering from the threshold up to c.m. energies of 1.9 GeV. Therefore, we develop a meson exchange model which describes #pi#N scattering in a system of the coupled reaction channels #pi#N, #sigma#N, #pi##DELTA#, #rho#N, #pi#N"*(1520), and #eta#N. Within this model a detailed analysis of the resonance N"*(1440) is performed. We find this resonance to be generated dynamically by the strong coupling to the #sigma#N channel. By using the speedplot method resonance parameters are extracted. Within a simplified model we demonstrate, that the large inelasticity, which is connected with the resonance N"*(1440), is generated by the often disregarded #sigma#N channel and that the #pi##DELTA# channel is less important. Furthermore, we investigate the resonance N"*(1520). We find, that it is indeed possible to generate this resonance as #rho#N bound state as suggested in earlier publications, but this is not in agreement with other observables. The importance of the resonance N"*(1520) as a contribution to the differential cross section of the reaction #pi#N#->##eta#N is seen as an interference, which leads to a strong angular dependence in this observable. (orig.)SIGLEAvailable from TIB Hannover: RA 831(3692) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman