1. The first measurement of the Michel parameter η in τ decays
- Author
-
Mikhail Danilov, Ivan Belyaev, G. Kostina, Klaus R. Schubert, T. S. Yoon, R. Schwierz, S. Weseler, A. Nau, Sergey Semenov, D. O. Litvintsev, R. Reiner, A. Kosche, Yuri Gershtein, B. Spaan, Hermann Kolanoski, D. Töpfer, I. Korolko, P. Pakhlov, P. Eckstein, H. Schröder, R. P. Hofmann, P. R.B. Saull, V. Lubimov, T. Siegmund, Werner Hofmann, Sebastian Nowak, D. Wegener, M. Schmidtler, R. G. Van de Water, I. Tichomirov, J. Stiewe, H. Wegener, K. T. Knöpfle, S. Chechelnitsky, R. Mundt, D. Reßing, P. Krieger, K. Ehret, A. Snizhko, C. Hast, H. Thurn, T. Podobnik, J. Spengler, Michael Schneider, E. Križnič, H. Kapitza, A. Hüpper, D. B. MacFarlane, Holger Schulz, K. Reim, J. D. Prentice, R. Waldi, Axel Lindner, T. Živko, A. Droutskoy, G. Kernel, A. Lange, C. Frankl, M. Walter, T. Oest, O. Mai, M. Schieber, R. Eckmann, Thomas Hamacher, Yu. Zaitsev, S. Werner, K. Tzamariudaki, P. Križan, A. Golutvin, W. Schmidt-Parzefall, Vladislav Balagura, H. Kuipers, T. Kirchhoff, H. Albrecht, R. Mankel, and R. Wurth
- Subjects
Physics ,Nuclear and High Energy Physics ,Particle physics ,Argus ,Electron–positron annihilation ,Hadron ,DESY ,Spectral line ,Vertex (geometry) ,Nuclear physics ,High Energy Physics::Experiment ,computer ,Storage ring ,computer.programming_language ,Lepton - Abstract
Using the ARGUS detector at the e+e - storage ring DORIS II at DESY, we have studied lepton energy spectra in ~- decays. We present a "pseudo-rest-frame" technique in which the second r in the event, decaying into a heavy hadronic system, is used as reference. This method allows for the first measurement of the Michel Parameter 7/in ~- decays. We also determine the Michel Parameter p in 7" --~ e~u decays with a precision comparable to the present world average. The measured values of the parameters p = 0.735 4- 0.036 4- 0.020 and r 1 = 0.03 4- 0.18 4- 0.12 are in good agreement with standard V-A coupling at the ~--~,-W vertex.
- Published
- 1995