Measurement of the Tau Neutrino Helicity and the Michel Parameters in Polarized e+e- Collisions

Abstract

We present a new measurement of the tau neutrino helicity, hnu and the tau Michel parameters rho, eta, xi and the product delta xi. The analysis exploits the highly polarized SLC electron beam to extract these quantities directly from a measurement of the tau decay spectra, using the 1993-1995 SLD data sample of 4328 e+e- --> Z0 --> tau+tau- events. From the decays tau --> pi nu(tau) and tau --> rho nu(tau) we obtain a combined value hnu=-0.93+/-0.10+/-0.04. The leptonic decay channels yield combined values of rho=0.72+/-0.09+/-0.03, xi=1.05+/-0.35+/-0.04 and delta xi=0.88+/-0.27+/-0.04.

10 pages, LaTex document, 2 figures all in gzip tar file. Also available in gzip-compressed postscript form (64 Kb) at http://www.slac.stanford.edu/~erez/hnutex/lorentz.ps.gz Uncompressed postscript file (214 Kb) available to DECNET users as SLACVX: :DISK$SLD_USR0:[EREZ.XXX]LORENTZ.PS to be published at Phys. Rev. Lett. 78 (June 1997)

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• Searching For Anomalous $\tau \nu W$ Couplings
• An experiment for the measurement of the bound-beta decay of the free neutron
• Determination of the Michel Parameters rho, xi, and delta in tau-Lepton Decays with tau --> rho nu Tags
• Spin Physics at e^+e^- Colliders