Measurement ofτbranching 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 ${pb}^{{{-}}1}at a center-of-mass energy of 29 GeV. The one- and three-charged-particle inclusive branching ratios of the τ decay are measured to be{B}₁=(84.7±1.0)% and{B}₃=(15.1±1.0)%, where{B}₁$+${B}₃$ is constrained to be 99.85%. The branching ratios of the two leptonic decay modes are B(${{τ}}^{{{-}}}→{e}^{{{-}}}ν{{}}ₑν_τ)=(18.4±{}1.6)% and B(τ^-{→}μ^- {ν}_μ{{ν}}_{{τ}})=(17.7±1.4)%. If we then assume lepton universality, we obtain B({{τ}}^{{{-}}}→{e}^{{{-}}}ν{{}}ₑν_τ)=(18.3±{}0.9)% and B(τ^-{→}μ^- {ν}_μ{{ν}}_{{τ}})=(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*^-{→}KSO{{{π}}}⁺π^-, we find B(τ^-{→}K^*-(892)+neutral particles)=(1.4±{}0.9)%. The quoted errors are the combined statistical and systematic errors.