Research Papers in Physics and Astronomy


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Published by American Physical Society. Phys. Rev. D 56, 5320 (1997). Copyright © 1997 American Physical Society. Permission to use.


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±νν̅ decay as well as the τ neutrino helicity parameter h in τ±→π±π0ν decay. From a data sample of 3.02×106 produced τ pairs we analyzed events of the topologies e+e-→τ+τ-→(l±νν̅)(π±π0ν) and e+e-→τ+τ-→(π±π0ν̅)(π±π0ν). 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 h=-0.995±0.010±0.003, where we have used the previously determined sign of h [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 standard model V-A interaction.

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