Measurement of the Michel Parameter $\rho$ in Muon Decay

TWIST Collaboration, J. R. Musser

The TWIST Collaboration has measured the Michel parameter $\rho$ in normal muon decay, ${\mu }^{+}\to e^{+}{\nu }_e{\bar{\nu }}_{\mu }$. In the Standard Model, $\rho$ = 3/4. Deviations from this value require…