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Photoproduction of charged pion pairs from hydrogen at energies up to 1500 MeV


Fretwell, Lyman Jefferson (1967) Photoproduction of charged pion pairs from hydrogen at energies up to 1500 MeV. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/KFYM-DK24.


Charged pion pair photoproduction has been investigated up to a gamma energy of 1500 MeV, using the Caltech 12-inch heavy liquid bubble chamber with a small diameter, high intensity photon beam passing through a central beam tube gaseous hydrogen target surrounded by the sensitive Freon. Scanning, analysis, and data reduction techniques have been developed to deal with the problems of two-vie stereo, hidden event origins, absence of magnetic field, and the range-energy and multiple scattering relationships that occur in the heavy materials. Roughly 5700 pictures have been scanned and analyzed, yielding 754 acceptable events. Cross section and parameter distributions are generally consistent with the results of previous experiments. A statistically insignificant “bump” was observed in the dipion mass spectrum in the region of 500 MeV, the disputed σ meson mass. This region was investigated as carefully as the limited statistics would allow; dipion angular distributions are consistent with isotropy, and there is indication that some of the events in this region might come from decay of an intermediate N*11 (1425) into a proton and dipion.

Photographic materials on pp. 18, 20, 22, and 24 are essential and will not reproduce clearly on Xerox copies. Photographic copies should be ordered.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Mullins, J. H.
Thesis Committee:
  • Unknown, Unknown
Defense Date:9 June 1966
Funding AgencyGrant Number
Atomic Energy CommissionUNSPECIFIED
Record Number:CaltechTHESIS:11302015-103822413
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9294
Deposited On:30 Nov 2015 21:47
Last Modified:09 Nov 2022 19:20

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