Improved tau polarisation measurement

D. Buskulic, D. Casper, I. De Bonis, D. Decamp, P. Ghez, C. Goy, J. P. Lees, M. N. Minard, P. Odier, B. Pietrzyk, F. Ariztizabal, M. Chmeissani, J. M. Crespo, I. Efthymiopoulos, E. Fernandez, M. Fernandez-Bosman, V. Gaitan, Ll Garrido, M. Martinez, S. OrteuA. Pacheco, C. Padilla, F. Palla, A. Pascual, J. A. Perlas, F. Sanchez, F. Teubert, D. Creanza, M. de Palma, A. Farilla, G. Iaselli, G. Maggi, N. Marinelli, S. Natali, S. Nuzzo, A. Ranieri, G. Raso, F. Romano, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, G. Zito, X. Huang, J. Lin, Q. Ouyang, T. Wang, Y. Xie, R. Xu, S. Xue, J. Zhang, L. Zhang, W. Zhao, G. Bonvicini, M. Cattaneo, P. Comas, P. Coyle, H. Drevermann, A. Engelhardt, R. W. Forty, M. Frank, M. Girone, R. Hagelberg, J. Harvey, R. Jacobsen, P. Janot, B. Jost, J. Knobloch, I. Lehraus, M. Maggi, C. Markou, E. B. Martin, P. Mato, H. Meinhard, A. Minten, R. Miquel, T. Oest, P. Palazzi, J. R. Pater, P. Perrodo, J. F. Pusztaszeri, F. Ranjard, P. Rensing, L. Rolandi, D. Schlatter, M. Schmelling, O. Schneider, W. Tejessy, I. R. Tomalin, A. Venturi, H. Wachsmuth, W. Wiedenmann, T. Wildish, W. Witzeling, J. Wotschack, Z. Ajaltouni, M. Bardadin-Otwinowska, A. Barres, C. Boyer, A. Falvard

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Abstract

Using 22 pb-1 of data collected at LEP in 1992 on the peak of the Z resonance, the ALEPH collaboration has measured the polarisation of the tau leptons decaying into {Mathematical expression}, πν, ρν and a1 ν from their individual decay product distributions. The measurement of the tau polarisation as a function of the production polar angle yields the two parameters N τ and N e, where, in terms of the axial and vector couplings g Al and g Vl, N l=2 g Vl gAl/(g Vl 2 +g Al 2 ). This analysis follows to a large extent the methods devised for the 1990 and 1991 data but with improvements which bring a better understanding of the systematic uncertainties. Combining the 1992 measurements with our previously published results yields N τ=0.136±0.012±0.009 and N e=0.129±0.016±0.005. Assuming e-τ universality, the measurements imply an effective weak mixing angle of sin 2 θ W eff =0.2332±0.0014. © 1996 Springer-Verlag.
Original languageEnglish
Pages (from-to)183-193
JournalZeitschrift für Physik C: Particles and Fields
Volume69
Issue number1
DOIs
Publication statusPublished - 1 Jan 1995

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    Buskulic, D., Casper, D., De Bonis, I., Decamp, D., Ghez, P., Goy, C., Lees, J. P., Minard, M. N., Odier, P., Pietrzyk, B., Ariztizabal, F., Chmeissani, M., Crespo, J. M., Efthymiopoulos, I., Fernandez, E., Fernandez-Bosman, M., Gaitan, V., Garrido, L., Martinez, M., ... Falvard, A. (1995). Improved tau polarisation measurement. Zeitschrift für Physik C: Particles and Fields, 69(1), 183-193. https://doi.org/10.1007/BF02907399