Photoproduction of Neutral Pions in Hydrogen from 500 to 950 Mev

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The process [...] has been studied by detecting recoil protons from a liquid hydrogen target which was bombarded by the bremsstrahlung beam of the California Institute of Technology electron synchrotron. The angle and momentum of the recoil protons were measured by a magnetic spectrometer-three scintillation counter coincidence system. The process has been studied between photon laboratory energies of 490 and 940 Mev. and between pion center-of-mass angles of [...] and [...]. Protons which arose from meson pair production were significant at forward laboratory angles. A correction for this contamination is discussed. The rapid decrease of the total cross section above 320 Mev. continues out to 600 Mev. and then rises slightly reaching a peak value around 800 Mev. The center-of-mass angular distributions are analyzed in a power series of the cosine of the pion angle and it is found that terms up to the fourth power are necessary to fit the data above 600 Mev. A multipole expansion is made assuming that mesons are produced in only S, P and D states; this expansion is used to show that no single multipole absorption is responsible for the rise in the cross section above 600 Mev