Measuring the Michel parameter xi ''

Unlike the majority of Michel parameters which are consistent with the Stan dard Model V-A interaction, the experimental value of xi " (= 0.65 +/- 0.36 ) [1] is poorly known. Our experiment will measure the longitudinal polariz ation, P-L, of positrons emitted from the decay of polarized muons. The val ue of P-L, equal to unity in the Standard Model, will decrease for high ene rgy positrons emitted antiparallel to the muon spin if the combination of M ichel parameters xi "/xi xi' -1 deviates from the Standard Model value of z ero.