Measurement of the spectral function for the ${\tau }^{-}\to K^{-}{K}_S{\nu }_{\tau }$ decay in BABAR experiment

The decay ${\tau }^{-}\to K^{-}{K}_S{\nu }_{\tau }$ has been studied using $430\times {10}^6$ $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$ events produced at a center-of-mass energy around 10.6 GeV at the PEP-II collider and studied with the BABAR detector. The mass spectrum of the $K^{-}{K}_S$ system has been measured and the spectral function has been obtained. The measured branching fraction ${\cal B}(\tau^{-}\to K^{-}K_S\nu_{\tau}) = (0.739\pm 0.011(\rm stat.)\pm 0.020(\rm syst.))\times 10^{-3}$ is found to be in agreement with earlier measurements.