Photoproduction of Neutral Pions at Energies 600 to 800 Mev

Abstract

The photoproduction of neutral $\ensuremath{\pi}$ 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\ifmmode^\circ\else\textdegree\fi{}, 30\ifmmode^\circ\else\textdegree\fi{}, 40\ifmmode^\circ\else\textdegree\fi{}, 50\ifmmode^\circ\else\textdegree\fi{}, and 60\ifmmode^\circ\else\textdegree\fi{} 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: $A+B{{cos\ensuremath{\theta}}_{\ensuremath{\pi}}}^{\ensuremath{'}}+C{{{cos}^{2}\ensuremath{\theta}}_{\ensuremath{\pi}}}^{\ensuremath{'}}$. These functions are qualitatively like those at lower energies; $B$ is small and $\ensuremath{-}\frac{A}{C}$ 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.