Measurement of the G asymmetry for the γp↦Nπ channels in the Δ(1232) resonance region

The G asymmetry of the γp↦Nπ reaction has been measured for the first time for Eγ = 340±14 MeV. This observable, for which very scarce published data exist, plays an important role to disentangle the contributions of the various nucleon resonances. The experiment, performed at the Mainz microtron MAMI, used a 4π-detector system, a linearly polarized, tagged photon beam, and a longitudinally polarized proton target.