University of Illinois Urbana-Champaign

Photoproduction of positive pions near threshold in hydrogen

Simpson, James D.

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Description

Title
Photoproduction of positive pions near threshold in hydrogen
Author(s)
Simpson, James D.
Issue Date
1964
Doctoral Committee Chair(s)
Goldwasser, E.L.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • photoproduction
  • positive pions
  • hydrogen
  • hydrogen threshold
  • hydrogen bubble chamber
  • meson tracks
Language
en
Abstract
An experiment has been done to improve available measurements of pi+ photoproduction cross sections very near threshold 0 To do this, a 1410 hydrogen bubble chamber was used in an X-ray beam with Emax = 230 MeV. Meson tracks could be observed from their origins in the photon beam. Only those events were used in which the '1T+ stopped and decayed in the visible region of the chamber. To suppress electron background, the X-ray beam from the University of Illinois petatron was hardened before it passed through the bubble chamber. Each X-ray pulse contained a total energy of about 106 MeV. A special high pressure ion chamber was used to monitor the beam flux. The uncertainty in the calibration of the monitor is about 2.4%0 From 435 0 000 sets of photographs u about 9100 usable protoproduction events were found. The scanning efficiency appears to be greater than 99%. The 90 0 center-of-momentum matrix-e1ement-squared is found to agree well with an evaluation of the theoretical prediction of Chew, Goldberger, Low, and Nambu (CGLN). the threshold value for the a. oc·oe coefficient is. ... found to be 21.1 ± 0.8 ~b/str. In conjunction with the theoretically predicted value for the minus-to-plus ratio and using a theorem by Kroll and Ruderman g a value of .0788 ± .0030 is obtained for the re-norma1ized pion-nucleon coupling constant
Type of Resource
text
Permalink
http://hdl.handle.net/2142/23959
Copyright and License Information
1964 James D. Simpson

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