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## Full-Text Articles in Physics

Constraints On The Tau Neutrino Mass And Mixing From Precise Measurements Of Tau Decay Rates, J. Swain, L. Taylor

#### Constraints On The Tau Neutrino Mass And Mixing From Precise Measurements Of Tau Decay Rates, J. Swain, L. Taylor

*John Swain*

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: τ¯→e¯ν⁻eντ, τ¯→μ¯ν⁻μντ, τ →π¯ντ, and τ →K¯ντ. 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 ...

A Method To Determine The Tau Neutrino Helicity Using Polarized Taus, M.-T. Dova, L. N. Epele, H. Fanchiotti, C.A. García Canal, P. E. Lacentre, J. D. Swain

#### A Method To Determine The Tau Neutrino Helicity Using Polarized Taus, M.-T. Dova, L. N. Epele, H. Fanchiotti, C.A. García Canal, P. E. Lacentre, J. D. Swain

*John Swain*

A method is presented to extract the tau neutrino helicity, or equivalently, the chirality parameter γVA, independent of any tau polarization which may be present. The method is thus well-suited to measurements using taus produced from the Z⁰ and is complementary to analyses using tau correlations since it provides the sign of the chirality parameter which is otherwise unavailable without recourse to lower energy experiments where taus are unpolarized. Results of Monte Carlo studies and comments regarding the use of technique in experiments are also included.