On the Nature of the tau Tau-neutrino W Coupling

The electron momentum spectrum observed in the decay tau ..-->.. ..nu../sub tau/e..nu../sub e/ is in good agreement with the V--A hypothesis. The measured value of the Michel parameter, rho = 0.72 +- 0.15, excludes a V + A current and disfavors pure V or A currents. The spectrum allows us to set an upper limit of 250 MeV/c/sup 2/ (95% confidence level) for the tau neutrino mass. Finally, by measuring the tau-lifetime upper limit of 2.3 x 10/sup -12/ sec (95% confidence level), we show that the square of the coupling constant at the tau-..nu../sub tau/-W vertex is at least 12% of full weak strength.