Direct Measurements of the Branching Fractions for the Semileptonic Decays $D^0\to K^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ and $D^0\to \ddot{I}{€}^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$

Abstract

Based on the data sample of 33 pb${}^{-1}$ collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, the absolute branching fractions for the semileptonic decays $D^0\to K^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ and $D^0\to \ddot{I}{€}^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ have been measured. In the system recoiling against $7584\pm 198\pm 341$ singly tagged ${\bar{D}}^0$ mesons, $87.2\pm 13.6$ events for $D^0\to K^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ and $9.3\pm 7.4$ events for $D^0\to \ddot{I}{€}^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ are observed. These yield the absolute branching fractions to be $BF(D^0\to K^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)=(3.55\pm 0.56\pm 0.59)$ and $BF(D^0\to \ddot{I}{€}^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)=(0.38\pm 0.30\pm 0.10)$. The measured branching fraction for $D^0\to K^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ was previously used to determine the ratio $\hat{I}“(D^0\to K^{-}\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)/\hat{I}“(D^{+}\to {\bar{K}}^0\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)$ combining the previously measured branching fraction for $D^{+}\to {\bar{K}}^0\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ by the BES Collaboration.

7 pages, 6 figures