A Precision Measurement Of Muon Decay

The (V - A) structure of the weak interaction was put into the standard model by hand in order to obtain agreement with experiments. These experiments, however, do not rule out relatively large deviations from this structure. Muon decay provides an ideal laboratory to test this structure, being a purely leptonic process. The TRIUMF Weak Interaction Symmetry Test (TWIST) will measure both the energy and emission-angle distribution of positrons from the decay of polarized muons. This will provide a simultaneous determination of the Michel parameters P(mu)xi, p and delta describing muon decay with a precision of a few parts in 10(4). Stringent limits may then be placed on the coupling constants, as well as the mass and mixing angle of a possible right-handed W boson (W-R). In this paper the formalism for muon decay is presented, TWIST is described, and the expected results axe discussed.