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UBC Theses and Dissertations

A measurement of the branching ratio, R=[mathematical description for a branching ratio] Berghofer, David


The Branching Ratio R= [See Thesis for formula] has been measured on the basis of 100,000 π→ev events. Pions were provided by the TRIUMF cyclotron. The muons produced by pion decay themselves subsequently decay via [Formula]. The mono-energetic positrons from pion decay and the "Michel" distribution of positrons from muon decay were simultaneously detected in a large NaI crystal. A raytracing experiment was also performed to accurately determine the response of the NaI. After radiative corrections, and corrections for bremsstrahlung, positron annihilation, and energy losses, a discrepancy of about 4% between the empirical π→ev[sub e] lineshape and the calculated lineshape remains. The source of this background has not yet been determined., Based on the number of positrons from pion decay and from muon decay detected during several "time bins", our result is R = (1.212 ± 0.017) x10⁻⁴ The value predicted for V-A coupling and muon-electron universality is R (theory) = 1.233x10⁻⁴

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