PHOTOPRODUCTION OF POSITIVE PIONS FROM HYDROGEN NEAR THRESHOLD
Thesis/Dissertation
·
OSTI ID:4666293
Differential cross sections were measured for positive pion photoproduction on hydrogen at low energies. Pions were produced in a polyethylene target, and the carbon contribution was subtracted by measuring the yield from a carbon target. The gamma rays were obtained from bremsstrahlung of the electron beam of the Stanford 1-Bev linear electron accelerator. The electron beam was not swept out of the path of the gamma beam, and direct electroproduction of pions in the target had to be taken into account. The pions were identified by momentum and range by using a magnet spectrometer and a scintillation counter telescope. Absolute values of the cross sections were obtained by calibrating the solid angle of the magnet with an alpha-particle source. Relative cross sections were also measured using a liquid-hydrogen target. The electroproduction background was eliminated in this case by sweeping the electron beam away from the target. These data agreed with those obtained with the solid target technique within the experimental accuracy of plus or minus 5%. The final results are in agreement with the theoretical predictions of Chew et al. as computed by Robinson, but disagree with the predictions of Ball. This disagreement may come from the fact that Ball neglected the small p-wave phase shifts. The threshold value of the photoproduction matrix element was found, by extrapolation using the theory of Chew et al., to be (15.9 plus or minus 0.5) mu b sr/sup -1/. (TCO)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-026641
- OSTI ID:
- 4666293
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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