Determination of the Michel parameters ρ, ξ, and δ in τ-lepton decays with τ → ρν tags

H. Albrecht, T. Hamacher, R. P. Hofmann, T. Kirchhoff, R. Mankel, A. Nau, S. Nowak, D. Reßing, H. Schröder, H. D. Schulz, M. Walter, R. Wurth, C. Hast, H. Kapitza, H. Kolanoski, A. Kosche, A. Lange, A. Lindner, M. Schieber, T. SiegmundH. Thurn, D. Töpfer, D. Wegener, C. Frankl, J. Graf, M. Schmidtler, M. Schramm, K. R. Schubert, R. Schwierz, B. Spaan, R. Waldi, K. Reim, H. Wegener, R. Eckmann, H. Kuipers, O. Mai, R. Mundt, T. Oest, R. Reiner, A. Rohde, W. Schmidt-Parzefall, J. Stiewe, S. Werner, K. Ehret, W. Hofmann, A. Hüpper, K. T. Knöpfle, J. Spengler, P. Krieger, D. B. MacFarlane, J. D. Prentice, P. R.B. Saull, K. Tzamariudaki, R. G. Van De Water, T. S. Yoon, M. Schneider, S. Weseler, M. Bračko, G. Kernel, P. Križan, E. Križnič, G. Medin, T. Podobnik, T. Zivko, V. Balagura, S. Barsuk, I. Belyaev, R. Chistov, M. Danilov, V. Eiges, L. Gershtein, Yu Gershtein, A. Golutvin, O. Igonkina, I. Korolko, G. Kostina, D. Litvintsev, P. Pakhlov, S. Semenov, A. Snizhko, I. Tichomirov, Yu Zaitsev

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2 Scopus citations


Using the ARGUS detector at the e+e- storage ring DORIS II, we have measured the Michel parameters ρ, ξ, and ξδ for τ± → l± νν̄ decays in τ-pair events produced at center of mass energies in the region of the γ resonances. Using τ± → ρ±ν as spin analyzing tags, we find ρe = 0.68 ± 0.04 ± 0.08, ξe = 1.12 ± 0.20 ± 0.09, ξδe = 0.57 ± 0.14 ± 0.07, ρμ = 0.69 ± 0.06 ± 0.08, ξμ = 1.25 ± 0.27 ± 0.14 and ξδμ = 0.72 ± 0.18 ± 0.10. In addition, we report the combined ARGUS results on ρ, ξ, and ξδ using this work und previous measurements.

Original languageEnglish (US)
Pages (from-to)179-187
Number of pages9
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1-2
StatePublished - Jul 9 1998
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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