Determination of the absolute branching fractions of $D^0\to K^{-}{e}^{+}\hat{I}{½}_e$ and $D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e$

Abstract

Using 2.93 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 $D^0\to K^{-}{e}^{+}\hat{I}{½}_e$ and $D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e$ 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 $e^{+}{e}^{-}\to D\bar{D}$, a new reconstruction method is employed to select events that contain candidates for both $D\to \bar{K}{e}^{+}\hat{I}{½}_e$ and $\bar{D}\to K{e}^{-}\bar{\hat{I}}{½}_e$ decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events containing $D\to \bar{K}{e}^{+}\hat{I}{½}_e$ and hadronic $\bar{D}$ 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 $\frac{\bar{\hat{I}}{“}_{D^0\to K^{-}{e}^{+}\hat{I}{½}_e}}{\bar{\hat{I}}{“}_{D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e}}=1.039\pm 0.021$. This ratio supports isospin symmetry in the $D^0\to K^{-}{e}^{+}\hat{I}{½}_e$ and $D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e$ decays within $1.9\ddot{I}ƒ$.

10 pages, 3 figure, 3 tables