Determination of the structure of τ decays in the reaction e+e- → τ+τ- → ϱ+vτϱ-v τ and a precision measurement of the τ-neutrino helicity

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. SiegmundB. Spaan, H. Thurn, D. Töpfer, D. Wegener, P. Eckstein, M. Schmidtler, M. Schramm, K. R. Schubert, R. Schwierz, R. Waldi, K. Reim, H. Wegener, R. Eckmann, H. Kuipers, O. Mai, R. Mundt, T. Oest, R. Reiner, 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, C. Frankl, M. Schneider, S. Weseler, G. Kernel, P. Križan, E. Križnič, T. Podobnik, T. Živko, V. Balagura, I. Belyaev, S. Chechelnitsky, M. Danilov, A. Droutskoy, Yuri Gershtein, A. Golutvin, I. Korolko, G. Kostina, D. Litvintsev, V. Lubimov, P. Pakhlov, S. Semenov, A. Snizhko, I. Tichomirov, Yu Zaitsev

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Abstract

Using the ARGUS detector at the DORIS II storage ring we have investigated the Lorentz structure of the electroweak interaction in semi-hadronic τ decays. Spin correlations in the process e+e- → τ+τ- → vτπ+ π0 vτπ-π0 are exploited for a measurement of the normalized product of the vector (gV) and axial vector (gA) couplings of the τ lepton, γinAV = 2 Re{gAgV*} (|gV|2). The correlations are sensitive to the product of the couplings in both τ decays: γAV2 = γAV- → ντW-) AV = -h(vτ)h(vτ). The measured value, γAV2 = 1.044±0.057±0.060, determines the relative sign of the neutrino helicities. Assuming CP invariance, the absolute value |γAV| = 1.022±0.028±0.030 was found to be incellent agreement with the Standard Model. The contribution of scalar (gs) or pseudoscalar (gP) couplings was also investigated. No evidence for a scalar-like coupling was found.

Original languageEnglish (US)
Pages (from-to)383-392
Number of pages10
JournalPhysics Letters B
Volume337
Issue number3-4
DOIs
StatePublished - Oct 13 1994

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics

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