MODEL-INDEPENDENT DETERMINATION OF K-MATRIX POLES AND RESIDUES IN THE DELTA(1232) REGION FROM THE MULTIPOLE DATA FOR PION-PHOTOPRODUCTION

Using only the analytic structure of the K matrix and the assumption that the Compton-scattering amplitude is small compared to strong and electrostrong amplitudes, we extract the pole position and the residues for the resonant multipoles, in a model-independent and background-free fashion, directly from the experimentally obtained multipole data base in the (1232) region, posing a challenge for QCD-inspired hadron models. © 1990 The American Physical Society.