We present preliminary absolute branching fraction measurements of leptonic $D_s^+$ decays to $\mu^+\nu_{ \mu}$ and $\tau^+\nu_{ \tau}$, and of hadronic $D_s^+$ decays to $K^-K^+\pi^+$, $\bar{ K}{ }^0K^+$ and $\eta\pi^+$. The results are obtained from a large data sample collected near the $\Upsilon(4S)$ and $\Upsilon(5S)$ resonances with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We obtain the the branching fractions ${ \cal B}(D_s^+\to\mu^+\nu_{ \mu})=(0.528\pm0.028\pm0.019)%$ and ${ \cal B}(D_s^+\to\tau^+\nu_{ \tau})=(5.70\pm0.21{ }^{ +0.31}_{ -0.30})%$ which are combined to determine the $D_s$ decay constant $\fds=(255.0\pm4.2\pm5.0)$ MeV, where the first and second uncertainties are statistical and systematic, respectively. Branching fractions of hadronic decays are measured to be ${ \cal B}(D_s^+\to K^-K^+\pi^+)=(5.06 \pm 0.15\pm 0.19)%$, ${ \cal B}(D_s^+\to\bar{ K}{ }^0K^+)=(2.84 \pm 0.12\pm 0.08)%$ and ${ \cal B}(D_s^+\to\eta\pi^+)=(1.79\pm0.14\pm 0.05)%$.
Categories: hep-ex