The photoproduction of charged pions from deuterium has been studied using a "monochromatic" gamma-ray beam of 292±8 Mev. The energy spectra of both positive and negative pions at the laboratory angle of 120° were determined and both agreed within experimental error with that predicted by the theory of Lax and Feshbach. The negative-to-positive ratio at 120° was 1.07±0.16, and within experimental error, was independent of meson energy. At an angle of 73° the ratio was 0.90±0.23 for 98.7 Mev mesons. The measured negative-to-positive ratio disagrees both with the simple classical picture of Brueckner and the phenomenological theory of Watson. Some results on the ratio using a bremsstrahlung beam are given.
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Protons of the internal circulating beam of the Bevatron were scattered in a polyethylene target. Both scattered and recoil protons were detected by scintillation counters at angles which define elastic proton-proton events. An internal counter was located within a few inches of the beam to permit measurements at laboratory scattering angles as low as 2°. Absolute values are based on the calibration of the induction electrode that monitors the circulating beam. Total elastic cross sections obtained by integrating the differential spectra are 17, 10, and 8 mb at 2.24, 4.40, and 6.15 Bev, respectively. The experimental angular distributions are consistent with the prediction of a simple optical model with a complex index of refraction at short range.
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The scattering of 139.5-Mev electrons in hydrogen gas at one-atmosphere pressure has been investigated using photographic emulsions. The beam of electrons from the Stanford Mark III linear accelerator, collimated to a diameter of 116 in., passed through the gas and was collected in a lead Faraday cup. Ilford C−2 emulsions, 50 μ thick, which were arranged symmetrically about the beam, detected the recoil protons. Measurements of the recoil angle γ and the range in the emulsion were made on the proton tracks. Only those events were accepted whose measured range and angle correlated within ±2.33 standard deviations of the distribution about the elastic kinematic range-angle curve calculated from the multiple scattering in the emulsion and the uncertainty in angle measurement. A total of 2350 tracks have been tabulated in the angular interval 54°<~γ<~78° giving a statistical error matching the systematic errors in plate geometry, beam integration, and track measurement. The results are compared with the Mott cross section integrated over the interval. The theoretical cross section was corrected for (a) proton recoil, (b) the proton magnetic moment, (c) the finite size of the proton's charge and magnetic moment, (d) the radiative correction, including the effect on the cross section of emission of real photons contributing to the observed recoil protons. The result is σexpσtheor=0.988±0.021 (probableerror), using a proton radius of 7.7×10−14 cm, and including a 2.74% radiative correction; the result is not sensitive to the choice of proton radius.
The radiative corrections were not applied in the calculation of the cross sections from the experimental data. Thus the cross sections given in the table are experiment-dependent because the radiative correction depends on the resolution of an experiment. The errors given in the table include systematic and statistical errors combined quadratically. The statistical error varies from 3.5% at 77 DEG to 23.6% at 55 DEG.
These cross sections were recalculated by ZOV from the experimental ones using a radiative correction (see fig.15). Thus they may be considered as an experiment-independent cross sections of a 'pure' process E- P --> E- P.
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