Measurement of the branching fraction of $D_s^{\ast +}\to e^{+}{e}^{-}{D}_s^{+}$

Abstract

The branching fraction of the electromagnetic Dalitz decay $D_s^{\ast +}\to e^{+}{e}^{-}{D}_s^{+}$ is measured with an $e^{+}{e}^{-}$ collision data sample collected by the BESIII experiment at center-of-mass energies between 4.128 and 4.226 $\mathrm{GeV}$, corresponding to a total integrated luminosity of 7.33 ${\mathrm{fb}}^{-1}$. The measurement yields the branching fraction $\mathcal{B}(D_s^{\ast +}\to e^{+}{e}^{-}{D}_s^{+})=(7.28\pm 0.61_{\mathrm{stat}}\pm 0.31_{\mathrm{syst}})\times 10^{-3}$. The result is consistent with the previous one, with a 2.5-fold improvement in precision. This provides an important input for constraining the parameters of theoretical models and for determining the absolute branching fractions of $D_s^{\ast +}\to \ddot{I}{€}^0{D}_s^{+}$ and $D_s^{\ast +}\to {\hat{I}}^3{D}_s^{+}$, measured with a relative method.

12 pages, 3 figures