A Study of One-Prong Tau Decays with a Charged Kaon
  From an analysis of the ionisation energy loss of charged particles selected from 110326 e+e- -> tau+tau- candidates recorded by the OPAL detector at e+e- centre-of-mass energies near the Z0 resonance, we determine the one-prong tau decay branching ratios:   Br(tau- -> nu_tau K- >=0h0) = 1.528 +- 0.039 +- 0.040 %   Br(tau- -> nu_tau K-) = 0.658 +- 0.024 +- 0.029 % where the h0 notation refers to a pi0, an eta, a K^0_S, or a K^0_L, and where the first uncertainty is statistical and the second is systematic. 
The OPAL collaboration, G. Abbiendi, et al