Decays of the heavy lepton, tau (1785)

Abstract

The structure of the weak hadronic current coupled to the tau is investigated via some of the hadronic decays of the tau. The vector current coupling is determined by measuring the tau ..-->.. rho ..nu../sub tau/ branching ratio. The axial-vector coupling is determined by measuring the tau ..-->.. ..pi.. ..nu../sub tau/ branching ratio. The Cabibbo structure of the hadronic current is established by observing the decay tau ..-->.. K*(890)..nu../sub tau/ and measuring its branching ratio. The branching ratios for the decays tau ..-->.. e anti ..nu../sub e/..nu../sub tau/ and tau ..-->.. ..mu.. anti ..nu../sub ..mu../..nu../sub tau/ are measured as a normalization for the hadronic decays and as a check on the validity of the measurements. The leptonic branching ratios agree well with previous experiments. From a kinematic fit to the pion energy spectrum in the decay tau ..-->.. ..pi.. ..nu../sub tau/, an upper limit (95% confidence level) of 245 MeV is placed on the tau neutrino mass. From a simultaneous fit of the center of mass energy dependence of the tau production cross section and the pion energy spectrum in the decay tau ..-->.. ..pi.. ..nu../sub tau/, the tau mass is determined to be 1.787 +- .010 GeV/c. All propertiesmore » of the tau measured here are consistent with it being a sequential lepton coupled to the ordinary weak hadronic current.« less