Well-established nucleon resonances revisited by double-polarization measurements

Understand

The first measurement is reported of the double-polarization observable G in photoproduction of neutral pions off protons, covering the photon energy range from 620 to 1120 MeV and the full solid angle.

• G describes the correlation between the photon polarization plane and the scattering plane for protons polarized along the direction of the incoming photon.
• The observable is highly sensitive to contributions from baryon resonances.
• The new results are compared to the predictions from SAID, MAID, and BnGa partial wave analyses.