Measurement of the strange spectral function in hadronic tau decays

Tau leptondecays with open strangenessin the finalstate are measured with the OPAL detector at LEP to determine the strangehadronic spectral function of the tau lepton. The decays tau(-) -->(Kpi)(-)nu(tau)(Kpipipi)(-)nu(tau) and (Kpipipi)(-)nu(tau) with finalstates consisting of neutral and charged kaons and pions have been studied. The invariant massdistributions of 93.4% of these finalstates have been experimentally determined. Monte Carlo simulations have been used for the remaining 6.6% and for the strange finalstates including eta mesons. The reconstructed strange finalstates, corrected for resolution effects and detection efficiencies, yield the strangespectral function of the tau lepton. The moments of the spectral function and the ratio of strangeto non- strangemoments, which are important input parameters for theoretical analyses, are determined. Furthermore, the branching fractionsB(tau(-) --> K(-)pi(o)nu(tau)) = (0.471 +/- 0.059( stat) +/- 0.023(sys))% and B(tau(-) --> K(-)pi(+)pi(-)nu(tau)) = (0.415 +/- 0.053( stat) +/- 0.040(sys))% have been measured.