Thesis--Ph. D., University of Hong Kong.

Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 60-63). Also available via the World Wide Web.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 120-122) Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 1976. / Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 1974. / Also available in print.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

A photon asymmetry measurement in radiative muon capture (RMC) on ⁴⁰Ca has been carried out in order to determine a value for the induced-pseudoscalar coupling constant (ցƿ), thereby allowing us to investigate the possible renormalisation effect for this coupling constant inside nuclear matter. Negative muons from the M20A channel at TRIUMF were stopped in a ⁴⁰Ca target. The resulting RMC photons were then converted by a 5 cm thick Nal converter placed immediately in front of our main detector, a Nal crystal of size 46 cm∅x51 cm. The purpose of the converter was to provide discrimination against the prolific high energy neutron background. From a fit to our time spectrum for the high-energy (57 MeV< E⋎ <95 MeV) photons, we were able to extract a value for the RMC photon asymmetry (⍺⋎). This time spectrum, with 5200 "clean" photons and a signal to noise ratio of ~7, showed the photon asymmetry quite clearly. With our measured value for the photon asymmetry: ⍺⋎ = 1.00±0.23, the predicted value of the induced-pseudoscalar coupling constant becomes: ցƿ = (0.0±⁸‧⁰₆․₇) ցA;, this range contains the (theoretical) unrenormalised value of Goldberger-Treiman: ցƿ ≈ 7 ցA⋅ / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The photon asymmetry (⍺⋎) and partial branching ratio (Rk>57), for radiative muon capture on ⁴⁰Ca, have been measured in order to determine the magnitude of the induced-pseudoscalar coupling constant, gp. A large Nal(Tl) crystal (46cm ϕ x 51cm) was used with an active Nal(Tl) converter (36cm x 30cm x 5cm) as the photon detector. The combined system had an energy resolution of 15% at 70 MeV; a factor of two improvement over previous similar experiments. Simultaneous measurements of the photon asymmetry and the partial branching ratio have been performed twice in the past. From a theoretical stand-point the photon asymmetry measurement is of greater interest as it represents the least nuclear model-dependent way of extracting gp. In the present experiment we have observed 3100 photons with energies greater than 57 MeV, after background subtraction. Of these, 2500 could be used in the determination of ⍺⋎. A value of ⍺⋎ = 1.32+⁺⁰֗⁵⁴˗₀․₄₇ is obtained from a fit to the photon time distribution. For the first time in such measurements the photon asymmetry was visible in the time spectrum and an unconstrained fit is able to reproduce its known frequency and phase. The extracted asymmetry allows for the first time a meaningful limit to be placed on gp which is free of the uncertainties associated with the extraction of gp from the partial branching ratio. Our asymmetry result implies gp < 5Agp, favouring a renormalization of the induced-pseudoscalar coupling constant. The partial branching ratio determined in this experiment is consistent with previous measurements. A model-dependent extraction of gp from Rk>57 yields gP ~ (7 ± 2)gA. As a consequence of this work an improved experiment has recently been successfully performed at TRIUMF with increased statistics, improved energy resolution, and an improvement of approximately a factor of 15 in the signal-to-noise ratio. We have also identified a potential systematic error of as large as 15% in the normalization of the photon asymmetry in past experiments. Such an error occurs from the use of the V—A asymmetry distribution rather than a bound decay asymmetry distribution when performing Monte Carlo calculations of the decay electron asymmetry. This error affects the estimation of the residual muon polarization which is used to normalize the photon asymmetry. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Physics / Doctoral / Doctor of Philosophy