Measurement of the Michel parameter rho in muon decay.
/ Authors
J. Musser, R. Bayes, Y. Davydov, P. Depommier, J. Doornbos, W. Faszer, C. Gagliardi, A. Gaponenko, D. Gill, P. Green
and 34 more authors
P. Gumplinger, M. Hasinoff, R. Henderson, J. Hu, B. Jamieson, P. Kitching, D. Koetke, A. Krushinsky, Y. Lachin, J. Macdonald, R. P. Macdonald, G. Marshall, E. Mathie, L. V. Miasoedov, R. Mischke, P. Nord, K. Olchanski, A. Olin, R. Openshaw, T. Porcelli, J. Poutissou, R. Poutissou, M. Quraan, N. Rodning, V. Selivanov, G. Sheffer, B. Shin, F. Sobratee, T. Stanislaus, R. Tacik, V. Torokhov, R. Tribble, M. Vasiliev, D. Wright
/ Abstract
The TWIST Collaboration has measured the Michel parameter rho in normal muon decay, mu(+)--> e(+)nu(e)nu (mu). In the standard model, rho = 3/4. Deviations from this value imply mixing of left- and right-handed muon and electron couplings. We find rho=0.750 80+/-0.000 32(stat) +/- 0.000 97(syst) +/- 0.000 23, where the last uncertainty represents the dependence of rho on the Michel parameter eta. This result sets new limits on the W(L)-W(R) mixing angle in left-right symmetric models.
Journal: Physical review letters