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McDonald, Steven Campbell

TRIUMF

This thesis reports the first measurement of the radiative muon capture photon energy spectrum from hydrogen, performed at TRIUMF. The partial branching ratio for photons greater than 58 Me V is measured using a large solid-angle photon pair spectrometer. With this measurement, the strength of the weak pseudoscalar coupling, gp, of the weak hadronic current for the nucleon has been obtained. This was determined by comparing the measured photon rate with the most recent relativistic calculation of Fearing and Beder which included the affect of the Δ(1232) nucleon resonance in the process. When a muon is captured by a proton at densities of liquid hydrogn, it occurs predominantly from one of two states, the ortho molecular state and the para molecular state. The muon capture probability varies considerably between the two, with the ortho state the dominant. At present there is some contention over the rate of transfer between these two states, this rate, λ₀p, can effect the total rate of capture. This rate must be known for an accurate determination of gp· Consequently, two values of gp have been obtained. One, using the measured ortho to para transition rate, λ₀p = 4.1 x 10⁴ giving a value of gp = 11.2 ± 2.5, approximately 34% higher then the Goldberger-Treiman prediction. The corresponding partial branching ratio for photons greater than 58 MeV was measured to be 1.80 ± 0.3 x 10-⁸. The second value was obtained using the theoretical prediction for the transfer rate to the ground para state, λ₀p = 7.1 x 10⁴. This gives a value of gp = 10.5 ± 2.2 with the equivalent partial branching ratio of 1.82 ± 0.3 x 10-⁸, 26% larger than the PCAC prediction.

Text

2019-03-06

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/68497

Unreviewed

http://creativecommons.org/licenses/by-nc-nd/4.0/