Structure functions and branching ratios of τ decay with three charged hadrons in the final state

The experiments reported were performed at the DORIS II e+e- storage ring using the ARGUS detector for examining the decays τ-→h-h-h+ντ and τ-→h-h+h-π0ντ of the tau lepton. Measurements of the branching ratios resulted in BR(τ-→h-h-h+ντ)=8.27±0.23stat±0.50syst[%] and BR(τ-→h-h+h-π0ντ)=4.67±0.39stat±0.30syst [%]. The hadronic final state of the decay τ-→h-h-h+ντ was analysed by performing a model-independent measurement of seven structure functions, applying the moments defined by Kuehn and Mirkes. The structure functions determined are in good agreement with the model established by Kuehn and Santamaria. For the first time, a scalar component in the decay τ-→h-h+ντ was analysed. For this purpose, the measured structure functions WSB and WSD were compared with the predictions of the model defined by Decker et al. for various values of the coupling strength fπ'. The derived likelihood function of the coupling strength of vertical stroke fπ'vertical stroke <0.055 GeV, with a confidence interval of 95%. From this and with a confidence interval of likewise 95%, the absolute branching ratio is determined to have an upper limit of BR(τ-→(π'→π+π-π-)ντ)<0.15%. (orig.)