We report on new measurements of Cabibbo-suppressed semileptonic $D_s^+$ decays using $3.19~\mathrm{ fb}^{ -1}$ of $e^+e^-$ annihilation data sample collected at a center-of-mass energy of 4.178~GeV with the BESIII detector at the BEPCII collider. Our results include branching fractions $\mathcal B({ D^+_s\rightarrow K^0 e^+\nu_{ e}})=(3.25\pm0.38({ \rm stat.})\pm0.16({ \rm syst.}))\times10^{ -3}$ and $\mathcal B({ D^+_s\rightarrow K^{ *0} e^+\nu_{ e}})=(2.37\pm0.26({ \rm stat.})\pm0.20({ \rm syst.}))\times10^{ -3}$ which are much improved relative to previous measurements, and the first measurements of the hadronic form-factor parameters for these decays. For $D^+_s\rightarrow K^0 e^+\nu_{ e}$, we obtain $f_+(0)=0.720\pm0.084({ \rm stat.})\pm0.013({ \rm syst.})$, and for $D^+_s\rightarrow K^{ *0} e^+\nu_{ e}$, we find form-factor ratios $r_V=V(0)/A_1(0)=1.67\pm0.34({ \rm stat.})\pm0.16({ \rm syst.})$ and $r_2=A_2(0)/A_1(0)=0.77\pm0.28({ \rm stat.})\pm0.07({ \rm syst.})$.
Categories: hep-ex