Measurement of τ branching ratios

We have measured the branching ratios for several τ decay modes. We use e+e-→τ+τ- events accumulated with the TPC/Two-Gamma facility at the SLAC e+e- storage ring PEP. The data correspond to an integrated luminosity of 77 pb-1 at a center-of-mass energy of 29 GeV. The one- and three-charged-particle inclusive branching ratios of the τ decay are measured to be B1=(84.7±1.0)% and B3=(15.1±1.0)%, where B1+B3 is constrained to be 99.85%. The branching ratios of the two leptonic decay modes are B(τ-→e- ν¯eντ)=(18.4±1.6)% and B(τ-→μ- ν¯μντ)=(17.7±1.4)%. If we then assume lepton universality, we obtain B(τ-→e- ν¯eντ)=(18.3±0.9)% and B(τ-→μ- ν¯μντ)=(17.8±0.9)%. We measure the Cabibbo-allowed semihadronic decay mode B(τ-→π-+neutral particles)=(47.0±1.5)%, and the Cabibbo-suppressed τ decay mode B(τ-→K-+neutral particles)=(1.6±0.4)%. By looking for associated photons, we find B(τ-→K-π0+neutral particles) to be (1.2±0.6)%. Using the channel K*-→KSOπ+π-, we find B(τ-→K*-(892)+neutral particles)=(1.4±0.9)%. The quoted errors are the combined statistical and systematic errors.