Photoproduction of charged pions from deuterium near threshold
Yoon, Taek-Soon
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https://hdl.handle.net/2142/23962
Description
Title
Photoproduction of charged pions from deuterium near threshold
Author(s)
Yoon, Taek-Soon
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
charged pions
deuterium
deuterium near threshold
liquid deuterium bubble chamber
Language
en
Abstract
"An experiment has been performed in order to improve existing
information on the behavior of the pi-photoproduction cross section near
threshold. To do this an X=ray beam from the University of Illinois
betatron was passed through a 14 inch liquid deuterium bubble chamber.
Each X ·-ray pulse (E max :: 230 MeV) contained a total energy of about
106 MeV. l'ne X.""ray beam wa.s hardened by means of a. standard beam
. hardening technique to reduce the electron background. The X-ray beam
monitor was calibrated with an uncertainty of ± 2.4%.
A total of 140,000 usable photographs were taken. About 5400
."" +
~ -photoproduction events and about 2700 ~ Qphotoproduction events were
found. Each ~=-event was identified by a kinematic fitting of the vertex,
and each n+=event was identified by a characteristic ~= ~ decay signature.
Results were compared with Baldin9s impulse approximation calculations
in order to obtain the matrix element for the ~=-photoproduction process
from a free neutron. The results agree with the previous experiment by
Adamovich et al. and with the photoproduction theory of Chew, Goldberger$
Low and Nambu. This result, however, was found to be sensitive to the
so-called Ucut~offgD parameter. The .., + . ~ to ~ ratio has been dete~ned for seven pion laboratory
energy and angle binsp using the ~+~events observed in deuterium.
Coulomb corrections have been applied to these results.
A. Chew=Low ti8unstable tar get ei extrapolation procedure was used in
order to obtain the cross section for the ~=-photoproduction process
from a free neutron. A. correction factor has been calculated to
eliminate the effects of the Coulomb interaction and specific n~clear
force interaction of the recoiling protons in the final state. The
result of this analysis agrees with the CGLN theory evaluated with a
coupling constant f 2= 0.·073 (=) ~ .003 and N being set to zero.
The extrapolation to threshold was carried out using the cross
section shape predicted by CGLN. The threshold value of BRa 0 ( .., ) Ci was
found to be 26.0! 1.0 ~b/ster. Comparing th~s with the result of the
latest ~ + experiment a't the University of Illinoisp the threshold t;J' -/t;+J'
ratio was found to be 1.23 + .06."
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