Measurement of the Michel parameters and the average τ neutrino helicity from τ decays in e+e− → τ+τ−

The Michel parameters ϱ, η, ξ, and ξδ, the chirality parameter ξh and the τ polarization Pτ are measured using 32012 τ pair decays. Their values are extracted from the energy spectra of leptons and hadrons in τ− → l−νlντ and τ− → π−ντ decays, the energy and decay angular distributions in τ− → ϱ−ντ decays, and the correlations in the energy spectra and angular distributions of the decay products.Assuming universality in leptonic and semileptonic …