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Gamma rays from the decay of neutral pions photoproduced in the bremsstrahlung beam of the Caltech synchrotron from high density deuterium and hydrogen gas have been observed with a Thallium Chloride crystal gamma ray spectrometer. Integral gamma ray yields and gamma ray energy spectra have been obtained for several bremsstrahlung endpoint energies from 0.6 to 1.08 Bev at [theta] = 60° and 120° with respect to the bremsstrahlung beam. The resulting integral D/H ratios show no significant variation with bremsstrahlung energy in this range; the ratio for [theta] = 60° may be a percent or so lower than that for [theta] = 120° but the average over energy and angle is consistent with [...] YH = = 0.94 +/- 0.02 per nucleon.
Gamma ray yields for 0.2 Bev ranges of incident photon energy have been calculated from the above integral yields using the photon difference method. The resulting differential D/H ratio may exhibit a broad minimum around 0.8 Bev. The results are consistent, however, with a constant value [...] = = 0.85 +/- 0.05 per nucleon, averaged over incident photon energy and spectrometer angle.
It was possible to separate to some extent those observed gamma rays coming from the decay of [...] photoproduced singly from those from [...] multiply photoproduced, on the basis of their different energy spectra. Cross sections for single [...] photo-production from hydrogen obtained from the "singles" gamma rays are in general (but not complete) agreement with those obtained by more precise methods by Vette and Worlock. The D/H ratios for singly photoproducing [...] may exhibit a maximum for incident photon energy about 0.8 to 0.9 Bev for [theta] = 120°. n/p ratios calculated from the D/H ratios for singly photopro.ducing [...] are equal to the [...] ratios from deuterium obtained by Neugebauer et al., within the rather large errors on the n/p for incident photon energy >= 0.8 Bev for both [theta] = 60° and [theta] = 120°. The n/p ratio is significantly lower than the -/+ for [...], [theta] = 120°, possibly higher for [...], [theta] = 60°.
Cross sections for multiply photoproducing [...] from hydrogen, obtained from the observed multiples gamma rays, are of the same order of magnitude (possibly somewhat larger) as those obtained for example by Bloch for charged pion pair production from hydrogen, and exhibit similar features: no large variation is apparent with incident photon energy, pion center of mass system angle or pion CMS kinetic energy. The D/H ratio for multiple [...] photoproduction is in general somewhat less than, but on the order of one, with possibly a minimum in the region around 0.8 to 0.9 Bev incident photon energy. The observed multiples gamma ray energy spectra are not measured with sufficient precision to distinguish between multiple pion kinetic energy spectra predicted on the bases of various proposed models for pion pair production. Some indication is found, however, that the observed pion kinetic energy spectrum (CMS) may be somewhat peaked toward higher energy for incident photon energies 0.7 and 0.8 Bev, toward lower energy for 0.9 and 0.99 Bev
