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Institute of High Energy Physics, Beijing 100049, People's Republic of China.
G.I. Budker Institute of Nuclear Physics SB RAS (BINP), Novosibirsk 630090, Russia.
Phys Rev Lett. 2023 Oct 6;131(14):141802. doi: 10.1103/PhysRevLett.131.141802.
Using 7.33 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}^{+}→e^{+}ν_{e}. Our data contain a signal of this decay with a statistical significance of 2.9σ. The branching fraction of D_{s}^{+}→e^{+}ν_{e} is measured to be (2.1_{-0.9_{stat}}^{+1.2}±0.2_{syst})×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}^{+} [(0.070±0.028) 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}^{+}}=(214_{-46_{stat}}^{+61}±44_{syst}) MeV, corresponding to an upper limit of 354 MeV at the 90% confidence level.
利用北京正负电子对撞机（BEPCII）上的北京谱仪III（BESIII）探测器采集的(7.33,\mathrm{fb}^{-1})的(e^{+}e^{-})对撞数据，我们首次报道了对纯轻子衰变(D_{s}^{+}\to e^{+}\nu_{e})的实验研究。我们的数据包含了该衰变的信号，统计显著性为(2.9\sigma)。测得(D_{s}^{+}\to e^{+}\nu_{e})的分支比为((2.1_{-0.9_{stat}}^{+1.2}\pm0.2_{syst})\times10^{-5})，在(90%)置信水平下对应的上限为(4.0\times10^{-5})。以格点量子色动力学（lattice QCD）计算预测的辐射衰变(D_{s}^{+})的总宽度([(0.070\pm0.028),\mathrm{keV}])作为输入，确定(D_{s}^{+})的衰变常数为(f_{D_{s}^{*+}}=(214_{-46_{stat}}^{+61}\pm44_{syst}),\mathrm{MeV})，在(90%)置信水平下对应的上限为(354,\mathrm{MeV})。
