MEASUREMENT OF THE KAON CONTENT OF 3-PRONG TAU-DECAYS

We present branching fraction measurements of three-prong decays of the tau- lepton based on data from the TPC/Two-Gamma detector at SLAC PEP. The decays are classified according to the identities of the charged tracks to give simultaneous measurements of B[tau- --> nu(tau)K-pi+pi-]=0.58(-0.13)+0.15% and B[tau- --> nu(tau)K-K+pi-]=0.15+0.15(-0.07)+0.09)%, and upper limits of B[tau- --> nu(tau)pi-K+pi-]<0.25% B[tau- --> nu(tau)K-pi+K-]<0.09%, and B[tau- --> nu(tau)K-K+K-]<0.21%, where additional neutrals may be present in each case. The branching fractions are normalized to the world average three-prong topological branching fraction and there is an estimated 20% systematic error in addition to the listed statistical errors. We find the mass distributions in the K-pi+pi- decay are consistent with K1 dominance, and obtain branching fractions of B[tau- --> nu(tau)K1-(1270)]=0.41(-0.35)+0.41% and B[tau- --> nu(tau)K1-(1400)]=0.76(-0.33)+0.40%