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UBC Theses and Dissertations

A direct measurement of pmu xi from muon decay Bueno, James


The asymmetry of the positron distribution in polarised muon decay provides confirmation that the weak interaction maximally violates parity conservation. Since 1957 the quantity Pmu xi has been measured with increasing precision, where Pmu is the polarisation of the muon, and xi is a parameter describing the asymmetry. Thus far the results have been consistent with the standard model using a (V-A) interaction. A new measurement of pmu xi using the TRIUMF Weak Interaction Symmetry Test (TWIST) spectrometer is presented in this thesis. The result is pmu xi = 1.00084 +- 0.00035 (stat.) -0.00063,+0.00165 (syst.), which is a factor of 3.2 more precise than a previous TWIST direct measurement, and a factor of 7.0 more precise than the pre-TWIST value. New limits are set on physics beyond the standard model, including the weak decay of right-handed muons, and left-right symmetric models where a (V+A) current is introduced to conserve parity at higher energies.

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