Direct Measurement of the Branching Fraction for the Decay of $D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e$ and Determination of $\hat{I}“(D^0\to K^{-}{e}^{+}\hat{I}{½}_e)/\hat{I}“(D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e)$

Abstract

The absolute branching fraction for the decay $D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e$ is determined using $5321\pm 149\pm 160$ singly tagged $D^{-}$ sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC collider. In the system recoiling against the singly tagged $D^{-}$ meson, $34.4\pm 6.1$ events for $D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e$ is observed. Those yield the absolute branching fraction to be $BF(D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e)=(8.95\pm 1.59\pm 0.67)$. The ratio of the two partial widths for the decays of $D^0\to K^{-}{e}^{+}\hat{I}{½}_e$ and $D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e$ is determined to be $\hat{I}“(D^0\to K^{-}{e}^{+}\hat{I}{½}_e)/\hat{I}“(D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e)=1.08\pm 0.22\pm 0.07$.

6 pages, 6 figures, Submitted to Physics Letters B