Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)




David S Armstrong


A precise measurement of the induced weak pseudoscalar coupling constant of the proton, gp, is of interest as a basic test of chiral symmetry breaking. This is the least well-known weak form factor of the nucleon. Muon capture experiments [Jonkmans et al., Phys. Rev. Lett. 77(1996)4512] have been used to measure gp. However, the interpretation of these muon capture experiments requires knowledge of the relative population of the muonic atomic and molecular states for muons in liquid hydrogen. In particular, lambda op, the transition rate between the ortho- and para-molecular states of the pmup molecule, needs to be known with precision. The only previous measurement [Bardin et al., Phys. Lett. 104B(1981)320.] of lambda op yielded a value of (4.1 +/- 1.4) x 10 4 s-1, significantly different than the theoretical prediction [Bakalov et al., Nucl. Phys. A384(1982)302.] of 7.1 x 104 s-1. A measurement of lambdaop using the time distribution of neutrons from muon capture was performed at TRIUMF during June--July 1999 and November 1999. The lambdaop measured in this experiment is (13.8 +/- 1.6) x 104 s-1 . The uncertainty is dominated by the statistical precision of the fit and the background due to the deuterium contamination in the protium target. The implications of this result for gp are discussed.



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