One-prong $\tau$ decays with kaons

Abstract.

One-prong $\tau$ decays into final states involving kaons are studied with about 161 000 $\tau^+\tau^-$ events collected by the ALEPH detector from 1991 to 1995. Charged kaons are identified by dE/dx measurement, while $K^0_L$'s are detected through their interaction in calorimeters. Branching ratios are measured for the inclusive mode, $B(\tau^-\rightarrow K^-X\nu_\tau)=(1.52 \pm 0.04\pm0.04)\%$, where X can be any system of neutral particles, and for the exclusive modes \[ \begin{array}{rcl} B(\tau^-\to K^-\nu_\tau) &=& (6.96\pm0.25\pm0.14)\times 10^{-3}, B(\tau^-\to K^-\pi^0\nu_\tau) &=& (4.44\pm0.26\pm0.24)\times 10^{-3}, B(\tau^-\to K^-\pi^0\pi^0\nu_\tau) &=& (0.56\pm0.20\pm0.15)\times 10^{-3}, B(\tau^-\to K^-\pi^0\pi^0\pi^0\nu_\tau) &=& (0.37\pm0.21\pm0.11)\times 10^{-3}, B(\tau^-\to K^-K^{0}\nu_\tau) &=& (1.62\pm0.21\pm0.11)\times 10^{-3}, B(\tau^-\to K^{-}K^{0}\pi^0\nu_\tau) & =& (1.43\pm 0.25\pm0.15)\times 10^{-3}, B(\tau^-\to \overline{K^0} \pi^{-}\nu_\tau) &=& (9.28\pm 0.45\pm0.34)\times 10^{-3}, B(\tau^-\to \overline{K^0} \pi^{-}\pi^0\nu_\tau) &=& (3.47\pm0.53\pm0.37)\times10^{-3}, \end{array} \] where the first error is statistical and the second is systematical. Upper limits for $B(\tau^-\to \overline{K^0}\pi^{-}\pi^0\pi^0\nu_\tau)$ and $B(\tau^-\to K^{-}K^{0}\pi^0\pi^0\nu_\tau)$ are also obtained. Mass spectra in the final states are investigated in order to study the relevant dynamics.