First Experimental Study of the Purely Leptonic Decay ${D}_{s}^{*+}\to {e}^{+}{\nu }_{e}$

Using $7.33\text{}\text{}{\mathrm{fb}}^{-1}$ of ${e}^{+}{e}^{-}$ collision data taken with the BESIII detector at the BEPCII collider, we report the first experimental study of the purely leptonic decay ${D}_{s}^{*+}\to {e}^{+}{\nu }_{e}$. Our data contain a signal of this decay with a statistical significance of $2.9\sigma $. The branching fraction of ${D}_{s}^{*+}\to {e}^{+}{\nu }_{e}$ is measured to be $\left({2.1}_{{-0.9}_{\mathrm{stat}}}^{+1.2}±{0.2}_{\mathrm{syst}}\right)×{10}^{-5}$, corresponding to an upper limit of $4.0×{10}^{-5}$ at the 90% confidence level. Taking the total width of the ${D}_{s}^{*+}$ [$\left(0.070±0.028\right)\text{}\text{}\mathrm{keV}$] predicted with the radiative ${D}_{s}^{*+}$ decay from the lattice QCD calculation as input, the decay constant of the ${D}_{s}^{*+}$ is determined to be ${f}_{{D}_{s}^{*+}}=\left({214}_{{-46}_{\mathrm{stat}}}^{+61}±4{4}_{\mathrm{syst}}\right)\text{}\text{}\mathrm{MeV}$, corresponding to an upper limit of 354 MeV at the 90% confidence level.