Theoretical implications of the TWIST experiment results

The TRIUMF Weak Interaction Symmetry Test (TWIST) experiment measures the momentum and direction of the positron from the decay of polarized muons with very high precision. The TWIST results represent the world's most precise measurement of the muon decay spectrum. The experiment expects to meet its ambitious goals of an order of magnitude improvement over pre-TWIST results for the muon decay parameters ρ, δ and Pμπξ. Our most recent published results combined with other experiments provide improved constraints on any deviations from the standard model. These results as well as the corresponding constraints on new physics are presented. The measures that have been taken to reduce the systematic uncertainties for the upcoming final result are described.