Measurements of Tau Lepton Production and Decay at SQRT.S = 29 GEV

Properties of the tau lepton were measured in data taken with the MAC detector at the PEP e('+)e('-) storage ring at the Stanford Linear Accelerator Center. Approximately 27000 tau-pair events were pro- duced at a center of mass energy of 29 GeV and about half of these were selected from the data in order to study various properties of the tau. Precise measurements of the leptonic branching ratios of the tau yielded B((tau) (--->) (nu)(,(tau))e(nu)(,e)) = 0.174 (+OR-) 0.008 (+OR-) 0.005 and B((tau) (--->) (nu)(,(tau))(mu)(nu)(,(mu))) = 0.177 (+OR-) 0.008 (+OR-) 0.005. A precise measurement of the pion branching ratio yielded B((tau) (--->) (nu)(,(tau))(pi)) = 0.106 (+OR-) 0.004 (+OR-) 0.008. A search for tau decays into five charged hadrons was performed and an upper limit on the branching ratio for this decay mode was set at 0.0027 at the 95% confidence level. The Michel parameter was measured with the leptonic energy spectra and was found to be 0.79 (+OR-) 0.11 (+OR-) 0.09, consistent with the V - A hypothesis for the (tau) (nu)(,(tau)) - W vertex. Measurements of the coupling constants of the tau to the weak neutral current were made by observation of the forward-backward energy asymmetry of the tau decay products and their average energy. These measurements yielded g(,a)('e)g(,v)('(tau)) = (0.26 (+OR-) 0.31) x (1 (+OR-) 0.012) and g(,v)('e)g(,a)('(tau)) = (-0.05 (+OR-) 0.21 (+OR-) 0.34) respectively, consistent with the Glashow-Weinberg-Salam model of electroweak interactions.