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The position and the residues of the delta resonance pole in pion photoproduction
1996
Physics Letters B
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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 Δ (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_Δ = - 0.035 - 0.046 i, resulting in an E2/M1 ratio for the "dressed" delta resonance of - 3.5 %.
doi:10.1016/0370-2693(96)00855-6
fatcat:2y7hb3t6gvh4vhmx4bhyly2bge