Abstract: Muon decay provides an excellent probe of the space-time structure of the weak interaction. The TWIST experiment is searching for new physics by measuring with high precision the momentum and angular dependence of e+ emitted from the decay of polarized μ+. The ultimate TWIST goal is to measure the Michel parameters ρ, δ, and Pμξ to a few parts in 104. The initial physics results of TWIST, improved measurements of ρ and δ, place new limits on physics beyond the Standard Model.

References: hep-ex/0409063, hep-ex/0410045.