Absolute Branching Fraction Measurements for Exclusive $D_s$ Semileptonic Decays

We measure the absolute branching fractions of $\Ds$ semileptonic decays where the hadron in the final state is one of $ϕ$, $η$, $\etap$, $\Ks$, $\Kstar$, and $f_0$, using $2.8 \times 10^5$ $\epm \to \Ds\Dsstar$ decays collected in the CLEO-c detector at a center-of-mass energy close to 4170 MeV. We obtain ${\cal B}(\Dsp\to ϕe^+ ν_e) =(2.29\pm 0.37 \pm 0.11)$%, ${\cal B}(\Dsp\to ηe^+ ν_e) =(2.48 \pm 0.29 \pm 0.13)$%, ${\cal B}(\Dsp\to \etap e^+ ν_e) =(0.91 \pm 0.33 \pm 0.05)$%, where the first uncertainties are statistical and the second are systematic. We also obtain ${\cal B}(\Dsp\to K^0 e^+ ν_e) =(0.37\pm 0.10 \pm 0.02)$%, and ${\cal B}(\Dsp\to K^{\star 0} e^+ ν_e) =(0.18 \pm 0.07 \pm 0.01)$%, which are the first measurements of Cabibbo suppressed exclusive $\Ds$ semileptonic decays, and, ${\cal B}(\Dsp\to f_0 e^+ ν_e) \times {\cal B}(f_0 \to \pip\pim) =(0.13\pm 0.04 \pm 0.01)$%. This is the first direct evidence of a semileptonic decay including a scalar meson in the final state.

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