THE POSITION AND THE RESIDUES OF THE DELTA-RESONANCE POLE IN PION-PHOTOPRODUCTION

We have analyzed the M(1+)((3/2)) and E(1+)((3/2)) multipole amplitude s of pion photoproduction in the framework of fixed-t dispersion relat ions. Applying the speed plot technique to our results for these multi poles, we have determined the position and the residues of the Delta ( 1232) resonance pole. The pole is found at total c.m. energy W = (1211 - 50i) MeV on the second Riemann sheet, and the ratio of the electric and magnetic residues is R(Delta) = -0.035 - 0.046i, resulting in an E2/M1 ratio for the ''dressed'' delta resonance of -3.5%.