A study of one-prong Tau decays with a charged kaon

Abstract.

From an analysis of the ionisation energy loss of charged particles selected from 110326 ${\rm e}^+{\rm e}^- \rightarrow \tau^+\tau^-$ candidates recorded by the OPAL detector at ${\rm e}^+{\rm e}^-$ centre-of-mass energies near the Z$^0$ resonance, we determine the one-prong tau decay branching ratios:

\begin{eqnarray*} {\rm Br}(\tau^- \rightarrow \nu_\tau{\rm K}^- \ge 0{\rm h}^0) &=& (1.528 \pm 0.039 \pm 0.040)\% \nonumber {\rm Br}(\tau^- \!\!\rightarrow\!\! \nu_\tau {\rm K}^-) & = & (0.658 \pm 0.027 \pm 0.029)\% \end{eqnarray*}

where the h$^0$ notation refers to a $\pi^0$, an $\eta$, a K$^0_{\rm S}$, or a K$^0_{\rm L}$, and where the first uncertainty is statistical and the second is systematic.