Neutral Pion Production in Deuterium and Hydrogen: Ratios

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Abstract
Neutral photopion production in deuterium and hydrogen has been studied by counting the decay photons singly. Pure gas targets were used. The photon counter consisted of three counters, the first in anticoincidence and the second and third in coincidence. The photon counting rate was obtained by taking the difference between the counting rates with a Pb converter alternately behind and in front of the anticoincidence counter. Data were obtained for 300-, 400-, and 500-Mev bremsstrahlung at laboratory angles of 30, 73, and 140°. An attempt to apply the photon-difference method was only moderately successful owing to poor control of the bremsstrahlung end point and the unfavorable shape of the neutral pion excitation curve. At 73° and 140° the data are consistent with a constant value of 0.90 per nucleon for the deuterium-to-hydrogen neutral photopion production ratio. At 30° and 300 Mev there is some evidence for a larger ratio, which points to constructive interference between production on the proton and neutron in the deuteron. The data are consistent with the predictions of the "symmetrical theory" concerning the coupling of neutral pions to nucleons and with Watson's phenomenological theory of photopion production.