Polarization of Recoil Protons from the Photoproduction of Neutral Pions in Hydrogen at 585 and 660 Mev.

Citation

Maloy, John Owen (1961) Polarization of Recoil Protons from the Photoproduction of Neutral Pions in Hydrogen at 585 and 660 Mev. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/418S-MZ02. https://resolver.caltech.edu/CaltechETD:etd-05052005-154404

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The polarization of the recoil proton in the photoproduction process [...] has been measured at laboratory photon energies of 585 and 660 Mev, at pion center-of-mass angles of 86 and 77 degrees respectively. Nuclear emulsion was used as a scatterer and detector to analyze the polarization of magnetically selected recoil protons emitted from a liquid hydrogen target. The target was bombarded by bremsstrahlung and electrons from the Stanford Mark III Linear Accelerator. The emulsion was area-scanned for scattering events; no evidence of left-right scanning bias was found. The polarization was calculated from the observed scattering distributions by the method of maximum likelihood, using values of the analyzing power of emulsion obtained at Harwell. Large polarizations were found, 56 ± 14 per cent at 585 Mev and 58 ± 19 per cent at 660 Mev; the 660 Mev value becomes 51 ± 14 per cent if events found in scanning by different methods at Rome and at Padua are included. The polarization is in the direction k x p, where k and p are the momentum vectors of the incident photon and recoil proton, respectively. The results are in agreement with measurements made elsewhere. It is shown that the polarizations and angular distributions observed in this reaction are consistent with the choice of odd parity for the second pion resonance, but are not consistent with the choice of even parity.

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