Constraints on the tau neutrino mass and mixing from precise measurements of tau decay rates

• Online Access: http://hdl.handle.net/2047/d20000426

We have derived constraints on the tau neutrino mass and fourth generation mixing from an analysis of the partial widths of tau lepton decays, in particular: τ̅→e̅ν^-eντ, τ̅→μ̅ν^-μντ, τ →π̅ντ, and τ →K̅ντ. We present predictions for the tau decay widths, allowing for a non-zero tau neutrino mass, mντ, and for mixing with a neutrino of mass mνL > MZ/2, which is parametrised using a Cabibbo-like mixing angle, ΘL. By comparison of these theoretical predictions with the experimental measurements, we obtain the following bounds at the 90% confidence level: mντ < 42 MeV and sin² ΘL < 0.014.