Tau Michel parameters and neutrino helicity at SLD

We present a new measurement of the tau neutrino helicity (h(nu tau)) and the Michel parameters (rho, xi and xi delta). The analysis exploits the highly polarized SLC electron beam to extract these quantities from a direct measurement of the tau decay spectra. The 1993-1995 SLD sample of 4316 e(+)e(-) --> Z(0) --> tau(+)tau(-) events was utilized. From the decays tau --> pi(K)nu(tau), tau --> rho nu(tau) we obtain h(nu tau)(pi) = -0.86 +/- 0.18(stat) +/- 0.03(syst), and h(nu tau)(rho) = -1.03 +/- 0.12(stat) +/- 0.04(syst) respectively, combined to h(nu tau) = -0.97 +/- 0.10 +/- 0.04. The leptonic decay channels yield the results: rho(e) = 0.68 +/- 0.14(stat) +/- 0.06(syst), xi(e) = 1.18 +/- 0.52(stat) +/- 0.04(syst), xi delta(e) = 0.79 +/- 0.44(stat) +/- 0.07(syst) from the tau --> e<(nu)over bar>(e) nu(tau) decay channel and: rho(mu) = 0.74 +/- 0.13(stat) +/- 0.06(syst), xi(mu) = 0.89 +/- 0.49(stat) +/- 0.08(syst), xi delta(mu) = 0.87 +/- 0.35(stat) +/- 0.05(syst) from the tau --> mu<(nu)over bar>(mu)nu(tau) channel, where the combined values are: rho = 0.71 +/- 0.09 +/- 0.05, xi = 1.03 +/- 0.36 +/- 0.05 and xi delta = 0.84 +/- 0.27 +/- 0.05.