Photoproduction of neutral pions in hydrogen from 500 to 950 mev

Citation

Vette, James I. (1958) Photoproduction of neutral pions in hydrogen from 500 to 950 mev. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-04112005-090012

Abstract

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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.

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