First Observation of the Decay ${\tau }^{-}\to K^{\ast -}\eta {\nu }_{\tau }$

Abstract

Using data recorded by the CLEO-II detector at CESR, we report the first measurement of the branching fraction for the decay of ${\tau }^{-}$ into $K^{\ast -}\eta {\nu }_{\tau }$. The measured branching fraction is (2.9 +- 0.8 +- 0.4) $10^{-4}$. We also measure the inclusive branching fractions without requiring the $K^{\ast }$ resonance: ${\tau }^{-}$ into $K_S{\pi }^{-}\eta {\nu }_{\tau }$, ${\tau }^{-}$ into $K^{-}{\pi }^0\eta {\nu }_{\tau }$. The measured branching fractions are (1.10 +- 0.35 +- 0.11) $10^{-4}$, (1.77 +- 0.56 +- 0.71) $10^{-4}$ respectively.

10 pages, postscript file also available through http://w4.lns.cornell.edu/public/CLNS