Measurement of the Branching Fraction for the Cabibbo-Suppressed Decayτ−→K*−(892)ντ

Abstract

This Letter presents a measurement of the branching fraction for the Cabibbo-suppressed decay ${\tau }^{-}\to K^{{*}^{-}}\mathrm{}\left(892\right)\mathrm{}{\nu }_{\tau }$ with use of data obtained with the Mark-II detector at SPEAR. Eleven events containing a $K^{{*}^{\pm }}\mathrm{}\left(892\right)\mathrm{}$ in coincidence with a muon or an electron of opposite charge were found in data which span the center-of-mass energy region $4.2<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<6.7\mathrm{}$ GeV. It was determined that $B[{\tau }^{-}\to K^{{*}^{-}}\mathrm{}(892\left)\mathrm{}{\nu }_{\tau }\right]=(1.7\mathrm{}\pm 0.7)$%. The absence of events at the $K^{{*}^{\pm }}\mathrm{}\left(1430\right)\mathrm{}$ yields a 2-standard-deviation upper limit $B[{\tau }^{-}\to K^{{*}^{-}}\mathrm{}(1430\left)\mathrm{}{\nu }_{\tau }\right]<\mathrm{}0.9\mathrm{}$%.