Photoproduction of Neutral Pions at Energies 600 to 800 Mev

The photoproduction of neutral $\pi$ mesons from hydrogen has been studied at the California Institute of Technology Synchrotron Laboratory by detecting recoil protons from a liquid hydrogen target irradiated by the synchrotron bremsstrahlung beam. The recoil protons were detected by a five-counter telescope. Data were taken at proton laboratory angles of 19°, 30°, 40°, 50°, and 60° at proton energies corresponding to photon energies of 600, 700, and 800 Mev. Angular distribution data are produced at these three energies and fitted with functions of the form: $A+B{{cos\theta }_{\pi }}^{\prime }+C{{{cos}^2\theta }_{\pi }}^{\prime }$. These functions are qualitatively like those at lower energies; $B$ is small and $-\frac{A}{C}$ is roughly 1.25. The total cross section is found to have a minimum at about 600 Mev, being slightly larger at 700 and 800 Mev.