Measurement of the Michel parameters and the average tau-neutrino helicity from tau decays at LEP

• Published in: Physics letters. B 1998-10, Vol.438 (3), p.405-416
• Main Authors: Alemanni, G., Anderhub, H., Andreev, V.P., Bagnaia, P., Bay, A., Berges, P., Bertucci, B., Biland, A., Blyth, S.C., Bobbink, G.J., Bock, R., Bourquin, M., Buijs, A., Busenitz, J., Cara Romeo, G., Chamizo, M., Chen, A., Chen, G., Chen, G.M., Chen, H.F., Chen, H.S., Clare, I., Clare, R., Cotorobai, F., Csilling, A., Dai, T.S., D'Alessandro, R., Degré, A., Deiters, K., Dierendonck, D.van, Dittmar, M., Fabre, M., Falciano, S., Filthaut, F., Forconi, G., Galaktionov, Yu, Gau, S.S., Goldfarb, S., Gougas, A., Gurtu, A., Hidas, P., Jin, B.N., Khan, R.A., Kienzle-Focacci, M.N., Kim, J.K., Kunin, A., Lacentre, P., Landi, G., Lebrun, P., Lecoq, P., Lee, H.J., Linde, F.L., Lu, Y.S., Lustermann, W., Mangeol, D., Marzano, F., Merola, L., Metzger, W.J., Mey, M.von der, van Mil, A.J.W., Moore, R., Moulik, T., Muheim, F., Newman, H., Nisati, A., Organtini, G., Passaleva, G., Pauluzzi, M., Paus, C., Pauss, F., Pei, Y.J., Pistolesi, E., Ren, D., Robohm, A., Sakar, S., Salicio, J., Schmidt-Kaerst, S., Shukla, J., Siedenburg, T., Stickland, D.P., Stone, H., Stoyanov, B., Swain, J.D., Ting, S.M., Tóth, J., Valente, E., Vogel, H., Vogt, H., Vorvolakos, A., Wallraff, W., Wang, J.C., Wang, X.L., Wu, S.X., Wynhoff, S., Xu, J., Xu, Z.Z., Yang, H.J., Zalite, Yu, Zhou, Y., Zichichi, A.
• Format: Article
• Language: English
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/S0370-2693(98)01082-X

Four of the Michel parameters and the average tau-neutrino helicity have been measured by analysing tau decay spectra in 147 pb −1of data collected by the L3 detector. The decays τ −→ e −ν τ ν ̄ e , τ −→ μ −ν τ ν ̄ μ , τ −→ π −ν τ , τ −→ ρ −ν τ and their charge conjugates were considered. The results: ρ=0.762±0.035, η=0.27±0.14, ξ=0.70±0.16, ξδ=0.70±0.11 and ξ h =−1.032±0.031 are consistent with a V−A structure for the weak charged current and lepton universality.