Direct measurement of B((D)(s)(+) going to (phi)(X))

Abstract

The absolute inclusive branching fraction of $D\sbsp{s}{+}\to\phi X$ has been measured from data collected by the BES detector at a center of mass energy of 4.03 GeV, corresponding to an integrated luminosity of 22.3 $pb\sp{-1}.$ At this energy $D\sb{s}$ mesons are produced in the reaction $e\sp{+}e\sp{-}\to D\sbsp{s}{+}D\sbsp{s}{-}.$ We have selected $D\sb{s}$ candidate events by reconstructing five hadronic decay modes $D\sbsp{s}{+}\to\phi\pi\sp{+},\ \bar K\sp{*0}K\sp{+},\ \bar K\sp0K\sp{+},\ f\sb0\pi\sp{+},$ and $K\sp0K\sp{-}\pi\sp{+}\pi\sp{+}$ and have searched for inclusive $\phi$'s in the recoiling $D\sbsp{s}{-}.$ We observed 3 $\phi$ candidates in the recoil of 166.4 $\pm$ 31.8 $D\sb{s}$ decays reconstructed from the five hadronic decay modes. This gives the first absolute branching ratio $B(D\sbsp{s}{+}\to\phi X)=(17.8\ \sbsp{-7.2}{+15.1}\ \sbsp{-6.3}{+0.6})\%.$