Determination of the Michel parameters and the tau neutrino helicity in tau decay

Using the CLEO II detector at the Cornell Electron Storage Ring operated at √s=10.6 GeV, we have determined the Michel parameters ρ, ξ, and δ in τ∓→l∓ vv̄ decay as well as the τ neutrino helicity parameter hvτ in τ∓→π∓π0v decay. From a data sample of 3.02×106 produced τ pairs we analyzed events of the topologies e+e-→τ+τ-→(l ±vv̄)(π∓π0v) and e+e-→τ+τ -→(π±±0v̄)(π ∓π0v). We obtain ρ=0.747ρ =0.747±0.010±0.006, ξ=1.007±0.040±0.015, ξδ=0.745±0.026±0.009, and hvτ=-0.995±0.010 ±0.003, where we have used the previously determined sign of hvτ [ARGUS Collaboration, H. Albrecht et al., Z. Phys. C 58, 61 (1993); Phys. Lett. B 349, 576 (1995)]. We also present the Michel parameters as determined from the electron and muon samples separately. All results are in agreement with the stansdard model V-A interaction