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 amplitudes of pion photoproduction in the framework of fixed-t dispersion relations. Applying the speed plot technique to our results for these multipoles, 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%.