TWIST: Measuring the Space-Time Structure of Muon Decay

Abstract

Abstract. TWIST, the TRIUMF Weak Interaction Symmetry Test, is a precision measurement of the energy and angular distributions of the positrons emitted in polarized muon decay. The goal is to search for new physics that leads to deviations of the Michel parameters ρ, δ , and P µ ξ from their Standard Model values. TWIST will determine these parameters to a few parts in 10 4 , an improvement of at least an order of magnitude in each case. At this level, TWIST will confront several proposed extensions to the Standard Model.