Using $2.93{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected with the BESIII detector at a center-of-mass energy of 3.773 GeV, we measure the absolute branching fractions of the decays $D^0\to K^{-}{e}^{+}{\nu }_e$ and $D^{+}\to {\overline{K}}^0{e}^{+}{\nu }_e$ to be $(3.567\pm 0.031_{\mathrm{stat}}\pm 0.025_{\mathrm{syst}})\%$ and $(8.68\pm 0.14_{\mathrm{stat}}\pm 0.16_{\mathrm{syst}})\%$, respectively. Starting with the process $e^{+}{e}^{-}\to D\overline{D}$, a new reconstruction method is employed to select events that contain candidates for both $D\to \overline{K}{e}^{+}{\nu }_e$ and $\overline{D}\to K{e}^{-}{\overline{\nu }}_e$ decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events containing $D\to \overline{K}{e}^{+}{\nu }_e$ and hadronic $\overline{D}$ decays. Combining our results with the lifetimes of the $D^0$ and $D^{+}$ mesons and the previous BESIII measurements leads to a ratio of the two decay partial widths of $\frac{{\overline{\mathrm{\Gamma }}}_{D^0\to K^{-}{e}^{+}{\nu }_e}}{{\overline{\mathrm{\Gamma }}}_{D^{+}\to {\overline{K}}^0{e}^{+}{\nu }_e}}=1.039\pm 0.021$. This ratio supports isospin symmetry in the $D^0\to K^{-}{e}^{+}{\nu }_e$ and $D^{+}\to {\overline{K}}^0{e}^{+}{\nu }_e$ decays within $1.9\sigma$.

• Received 17 April 2021
• Accepted 15 July 2021

DOI:https://doi.org/10.1103/PhysRevD.104.052008

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Published by the American Physical Society