Backward Photoproduction ofπ0in the Region of theP33Pion-Nucleon Resonance

The ${\pi }^0$ photoproduction cross section has been measured at 180° for photon energies from 220 to 380 MeV, in steps of 20 MeV, by detecting the recoil proton at 0°. The statistical accuracy of the measurements varies between 3 and 7%, depending on the energy. Absolute cross sections have been deduced from a comparison of the measurements with electron-proton scattering. The experimental data are compared with theoretical results calculated from fixed-momentum-transfer dispersion relations. Special attention is paid to the prediction of the multipoles at the first resonance, namely, ${E_{1+}}^{\frac{3}{2}}$, ${M_{1+}}^{\frac{3}{2}}$, and ${E_{0+}}^{{\pi }^0}$ to obtain agreement with experiment.