A Measurement of the Michel Parameters in Leptonic Decays of the Tau

R. Ammar, P. Baringer, A. Bean, D. Besson, D. Coppage, C. Darling, R. Davis, N. Hancock, S. Kotov, I. Kravchenko, N. Kwak, S. Anderson, Y. Kubota, M. Lattery, J. J. O’Neill, S. Patton, R. Poling, T. Riehle, V. Savinov, A. SmithM. S. Alam, S. B. Athar, Z. Ling, A. H. Mahmood, H. Severini, S. Timm, F. Wappler, A. Anastassov, S. Blinov, J. E. Duboscq, D. Fujino, R. Fulton, K. K. Gan, T. Hart, K. Honscheid, H. Kagan, R. Kass, J. Lee, M. B. Spencer, M. Sung, A. Undrus, R. Wanke, A. Wolf, M. M. Zoeller, B. Nemati, S. J. Richichi, W. R. Ross, P. Skubic, M. Wood, M. Bishai, CLEO Collaboration

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10 Scopus citations


We have measured the spectral shape Michel parameters ρ and η using leptonic decays of the τ, recorded by the CLEO II detector. Assuming e - μ universality in the vectorlike couplings, we find ρ = 0.735 ± 0.013 ± 0.008, where the first error is statistical and the second systematic. We also present measurements for the parameters for e and μ final states separately.

Original languageEnglish (US)
Pages (from-to)4686-4690
Number of pages5
JournalPhysical review letters
Issue number25
StatePublished - Jun 23 1997


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