Muon decay parameters and the TWIST experiment
The TRIUMF Weak Interaction Symmetry Test (TWIST) collaboration has completed a simultaneous measurement of the muon decay parameters ρ, δ, and Pμξ , improving the precision of each by about one order of magnitude compared to the best previous experiments. The results test predictions of the standard model (SM) in a purely leptonic process and provide improved limits for relevant extensions to the SM. The talk will focus on successes and surprises encountered in the process of reducing systematic uncertainties to the level of 10-4 of the parameter values [2,3]. The final results as well as implications for physics beyond the SM will be summarized.
1. R. Bayes et al., Phys. Rev. Lett. 106, 041804 (2011).
2. J.F. Bueno et al., Phys. Rev. D 84, 032005 (2011).
3. A. Hillairet et al., Phys. Rev. D 85, 092013 (2012).