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

Authors

J. P. Alexander, Cornell University
Kenneth A. Bloom, University of Nebraska-LincolnFollow
CLEO Collaboration

Date of this Version

11-1-1997

Comments

Published by American Physical Society. Phys. Rev. D 56, 5320 (1997). http://prd.aps.org. Copyright © 1997 American Physical Society. Permission to use.

Abstract

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_vτ 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_vτ=-0.995±0.010±0.003, where we have used the previously determined sign of h_vτ [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.