Improved measurement of the semileptonic decay ${D}_{s}^{+}\to {K}^{0}{e}^{+}{\nu }_{e}$

Analyzing ${e}^{+}{e}^{-}$ collision data corresponding to an integrated luminosity of $7.33\text{}\text{}{\mathrm{fb}}^{-1}$ collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we measure the branching fraction of the semileptonic decay ${D}_{s}^{+}\to {K}^{0}{e}^{+}{\nu }_{e}$ to be $\left(2.98±0.2{3}_{\mathrm{stat}}±0.1{2}_{\mathrm{syst}}\right)×{10}^{-3}$. Based on fit to the partial decay rates in various ${q}^{2}$ intervals, the product value of ${D}_{s}^{+}\to {K}^{0}$ hadronic form factor and Cabibbo-Kobayashi-Maskawa element is measured to be ${f}_{+}^{{K}^{0}}\left(0\right)|{V}_{cd}|=0.143±0.01{1}_{\mathrm{stat}}±0.00{3}_{\mathrm{syst}}$. With $|{V}_{cd}|=0.22486±0.00067$ as an input, the hadronic form factor is evaluated to be ${f}_{+}^{{K}^{0}}\left(0\right)=0.636±0.04{9}_{\mathrm{stat}}±0.01{3}_{\mathrm{syst}}$. The branching fraction and form factor measurements are factors of 1.6 and 1.7 more precise than the previous world averages, respectively.