Phys. Rev. Lett.
78,
4686–4690
(1997)
A Measurement of the Michel Parameters in Leptonic Decays of the Tau
R. Ammar et al. (CLEO Collaboration)
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R. Ammar1, P. Baringer1, A. Bean1, D. Besson1, D. Coppage1, C. Darling1, R. Davis1, N. Hancock1, S. Kotov1, I. Kravchenko1, N. Kwak1, S. Anderson2, Y. Kubota2, M. Lattery2, J. J. O'Neill2, S. Patton2, R. Poling2, T. Riehle2, V. Savinov2, A. Smith2, M. S. Alam3, S. B. Athar3, Z. Ling3, A. H. Mahmood3, H. Severini3, S. Timm3, F. Wappler3, A. Anastassov4, S. Blinov4, J. E. Duboscq4, D. Fujino4, R. Fulton4, K. K. Gan4, T. Hart4, K. Honscheid4, H. Kagan4, R. Kass4, J. Lee4, M. B. Spencer4, M. Sung4, A. Undrus4, R. Wanke4, A. Wolf4, M. M. Zoeller4, B. Nemati5, S. J. Richichi5, W. R. Ross5, P. Skubic5, M. Wood5, M. Bishai6, J. Fast6, E. Gerndt6, J. W. Hinson6, N. Menon6, D. H. Miller6, E. I. Shibata6, I. P. J. Shipsey6, M. Yurko7, L. Gibbons7, S. D. Johnson7, Y. Kwon7, S. Roberts7, E. H. Thorndike7, C. P. Jessop8, K. Lingel8, H. Marsiske8, M. L. Perl8, S. F. Schaffner8, D. Ugolini8, R. Wang8, X. Zhou8, T. E. Coan9, V. Fadeyev9, I. Korolkov9, Y. Maravin9, I. Narsky9, V. Shelkov9, J. Staeck9, R. Stroynowski9, I. Volobouev9, J. Ye9, M. Artuso10, A. Efimov10, F. Frasconi10, M. Gao10, M. Goldberg10, D. He10, S. Kopp10, G. C. Moneti10, R. Mountain10, Y. Mukhin10, S. Schuh10, T. Skwarnicki10, S. Stone10, G. Viehhauser10, X. Xing10, J. Bartelt11, S. E. Csorna11, V. Jain11, S. Marka11, A. Freyberger12, D. Gibaut12, R. Godang12, K. Kinoshita12, I. C. Lai12, P. Pomianowski12, S. Schrenk12, G. Bonvicini13, D. Cinabro13, R. Greene13, L. P. Perera13, B. Barish14, M. Chadha14, S. Chan14, G. Eigen14, J. S. Miller14, C. O'Grady14, M. Schmidtler14, J. Urheim14, A. J. Weinstein14, F. Würthwein14, D. M. Asner15, D. W. Bliss15, W. S. Brower15, G. Masek15, H. P. Paar15, J. Gronberg16, R. Kutschke16, D. J. Lange16, S. Menary16, R. J. Morrison16, S. Nakanishi16, H. N. Nelson16, T. K. Nelson16, C. Qiao16, J. D. Richman16, D. Roberts16, A. Ryd16, H. Tajima16, M. S. Witherell16, R. Balest17, B. H. Behrens17, K. Cho17, W. T. Ford17, H. Park17, P. Rankin17, J. Roy17, J. G. Smith17, J. P. Alexander18, C. Bebek18, B. E. Berger18, K. Berkelman18, K. Bloom18, D. G. Cassel18, H. A. Cho18, D. M. Coffman18, D. S. Crowcroft18, M. Dickson18, P. S. Drell18, K. M. Ecklund18, R. Ehrlich18, R. Elia18, A. D. Foland18, P. Gaidarev18, R. S. Galik18, B. Gittelman18, S. W. Gray18, D. L. Hartill18, B. K. Heltsley18, P. I. Hopman18, S. L. Jones18, J. Kandaswamy18, N. Katayama18, P. C. Kim18, D. L. Kreinick18, T. Lee18, Y. Liu18, G. S. Ludwig18, J. Masui18, J. Mevissen18, N. B. Mistry18, C. R. Ng18, E. Nordberg18, M. Ogg18, J. R. Patterson18, D. Peterson18, D. Riley18, A. Soffer18, C. Ward18, M. Athanas19, P. Avery19, C. D. Jones19, M. Lohner19, C. Prescott19, S. Yang19, J. Yelton19, J. Zheng19, G. Brandenburg20, R. A. Briere20, Y. S. Gao20, D. Y.-J. Kim20, R. Wilson20, H. Yamamoto20, T. E. Browder21, F. Li21, Y. Li21, J. L. Rodriguez21, T. Bergfeld22, B. I. Eisenstein22, J. Ernst22, G. E. Gladding22, G. D. Gollin22, R. M. Hans22, E. Johnson22, I. Karliner22, M. A. Marsh22, M. Palmer22, M. Selen22, J. J. Thaler22, K. W. Edwards23, A. Bellerive24, R. Janicek24, D. B. MacFarlane24, K. W. McLean24, P. M. Patel24, and A. J. Sadoff25 (CLEO Collaboration)
1University of Kansas, Lawrence, Kansas 66045
2University of Minnesota, Minneapolis, Minnesota 55455
3State University of New York at Albany, Albany, New York 12222
4Ohio State University, Columbus, Ohio 43210
5University of Oklahoma, Norman, Oklahoma 73019
6Purdue University, West Lafayette, Indiana 47907
7University of Rochester, Rochester, New York 14627
8Stanford Linear Accelerator Center, Stanford University, Stanford,California 94309
9Southern Methodist University, Dallas, Texas 75275
10Syracuse University, Syracuse, New York 13244
11Vanderbilt University, Nashville, Tennessee 37235
12Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
13Wayne State University, Detroit, Michigan 48202
14California Institute of Technology, Pasadena, California 91125
15University of California, San Diego, La Jolla, California 92093
16University of California, Santa Barbara, California 93106
17University of Colorado, Boulder, Colorado 80309-0390
18Cornell University, Ithaca, New York 14853
19University of Florida, Gainesville, Florida 32611
20Harvard University, Cambridge, Massachusetts 02138
21University of Hawaii at Manoa, Honolulu, Hawaii 96822
22University of Illinois, Champaign-Urbana, Illinois 61801
23Carleton University, Ottawa, Ontario, Canada K1S 5B6 and the Institute of Particle Physics, Canada
24McGill University, Montréal, Québec, Canada H3A 2T8 and the Institute of Particle Physics, Canada
25Ithaca College, Ithaca, New York 14850
Received 26 December 1996; published in the issue dated 23 June 1997
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 ρeμ = 0.735±0.013±0.008 and ηeμ = -0.015±0.061±0.062, where the first error is statistical and the second systematic. We also present measurements for the parameters for e and μ final states separately.
© 1997 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.78.4686
DOI:
10.1103/PhysRevLett.78.4686
PACS:
13.35.Dx, 14.60.Fg, 14.80.Cp
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