New measurements of muon decay from TWIST

The TRIUMF Weak Interaction Symmetry Test (TWIST) has recently completed its first physics analyzes. The results represent a significant increase in precision for two of the four Michel parameters describing the energy and angle distributions of positrons from polarized positive muon decay. This is the first step toward our eventual goal of improving upon previous determinations for three of the parameters by at least an order of magnitude, as a test of the Standard Model in the purely leptonic decay interaction. TWIST uses a polarized muon beam stopping at the center of a spectrometer consisting of a low mass, high precision array of planar drift chambers in a two tesla solenoidal field. The talk will focus on the operation of the device and the methods which are used to extract the decay parameters in a reliable way. Systematic uncertainties are especially important, as they will limit the final results. (author)