The helicity amplitudes A$_{1/2}$ and A$_{3/2}$ for the D$_{13}(1520)$   resonance obtained from the $\vec{\gamma} \vec{p} \to p \pi^0$ reaction}
  The helicity dependence of the $\vec{\gamma} \vec{p} \to p \pi^0$ reaction has been measured for the first time in the photon energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4$\pi$-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the $D_{13}(1520)$ resonance and are used to determine its parameters. 
GDH- and A2-Collaborations: J. Ahrens, et al