Determination of the E2/M1 Ratio in the γN \to Δ(1232) Transition from a Simultaneous Measurement of p(\vecγ,p)π^0 and p(\vecγ,π^+)n

Abstract

Tagged linearly polarized photons have been used at the Mainz Microtron MAMI for simultaneous measurements of the p(\vecγ,p)π^0 and p(\vecγ,π^+)n reaction channels to study the γN \to Δ(1232) transition. The energy dependence of the magnetic dipole M_{1+}^{3/2} and electric quadrupole E_{1+}^{3/2} amplitudes have been extracted from these data in the photon energy range from 270 to 420 MeV. The E2/M1 ratio for the γN \to Δ(1232) transition has been determined to be - (2.5+-0.1_{stat}+-0.2_{sys}) % at the resonance position delta_{33}=90^0.