Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

Measurement of the neutral-pion form factor by means of the reaction. pi. /sup 0/. -->. e/sup +/e. sqrt gamma

Thesis/Dissertation ·
OSTI ID:5947344
The slope parameter a of the ..pi../sup 0/-electromagnetic transition form factor was obtained from a measurement of the partial branching ratio of the Dalitz decay ..pi../sup 0/ ..-->.. e/sup +/e/sup -/..gamma.. into high invariant-mass electron-positron pairs. The experiment was carried out at the TRIUMF cyclotron laboratory. A beam of ..pi../sup -/ mesons was stopped in a liquid hydrogen target to produce neutral pions in the reaction ..pi../sup -/ p ..-->.. n ..pi../sup 0/. The electron-positron pairs were detected with two delay-line chamber telescopes, each followed by a large Nal crystal. A third Cal crystal measured the number of ..pi../sup 0/'s in the target by counting the photons from the decay ..pi../sup 0/ ..cap alpha.. ..gamma.. ..gamma... Data was taken at three detector opening angles 60/sup 0/, 130/sup 0/ and 156/sup 0/. The 60/sup 0/ measurement confirms the authors normalization. A value a = - 0.01 +/- 0.035 + 0.07/-0.05, where the first error is due to statistics and the second is an estimate of systematic effects, was obtained from the 130/sup 0/ geometry. This value does not support the result of the most recent previous experiment and is in accord with most theoretical calculations indicating that there is no unexpected structure in the ..pi../sup 0/ decay form factor.
Research Organization:
Oregon State Univ., Corvallis (USA)
OSTI ID:
5947344
Country of Publication:
United States
Language:
English