Precision measurement of the muon decay parameters {rho} and {delta}
- University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada)
- TRIUMF, Vancouver, British Columbia, V6T 2A3 (Canada)
The TWIST Collaboration has performed new measurements of two of the parameters that describe muon decay: {rho}, which governs the shape of the overall momentum spectrum, and {delta}, which governs the momentum dependence of the parity-violating decay asymmetry. This analysis gives the results {rho}=0.750 14{+-}0.000 17(stat){+-}0.000 44(syst){+-}0.000 11({eta}), where the last uncertainty arises from the correlation between {rho} and the decay parameter {eta}, and {delta}=0.750 67{+-}0.000 30(stat){+-}0.000 67(syst). These are consistent with the value of 3/4 given for both parameters in the standard model of particle physics, and are a factor of two more precise than the measurements previously published by TWIST. A new global analysis of all available muon decay data incorporating these results is presented. Improved lower and upper limits on the decay parameter P{sub {mu}}{sup {pi}}{xi} of 0.995 24<P{sub {mu}}{sup {pi}}{xi}{<=}{xi}<1.000 91 at 90% confidence are determined, where P{sub {mu}}{sup {pi}} is the polarization of the muon when it is created during pion decay, and {xi} governs the muon decay asymmetry. These results set new model-independent constraints on the possible weak interactions of right-handed particles. Specific implications for left-right symmetric models are discussed.
- OSTI ID:
- 21250584
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 78, Issue 3; Other Information: DOI: 10.1103/PhysRevD.78.032010; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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