Analyticity of the Scattering Amplitude and Resonance Parameters in the Meson Exchange Picture

Michael Doering, 
Forschungszentrum Juelich, Germany

The determination of the analytic structure of the scattering amplitude 
allows for a precise extraction of resonance parameters such as pole 
positions and residues, in case sufficiently precise data are available 
for all relevant channels. This model independent description of 
baryonic resonances permits one to compare the resonance spectrum to 
theoretical approaches like quark models and lattice QCD.

The Julich model of piN interaction is used to extract the resonance 
parameters. This coupled channel formalism based on a field-theoretical 
approach ensures the full analyticity. Also, recent results for the 
photoproduction are addressed. The unified description of different 
reactions improves the understanding of the meson-baryon dynamics from 
piN threshold beyond the second resonance region.