Observation of the Singly Cabibbo-Suppressed Decay $D^{+}\to \ddot{I}‰\ddot{I}{€}^{+}$ and Evidence for $D^0\to \ddot{I}‰\ddot{I}{€}^0$

Abstract

Based on 2.93 fb${}^{-1}$ $e^{+}{e}^{-}$ collision data taken at center-of-mass energy of 3.773 GeV by the BESIII detector, we report searches for the singly Cabibbo-suppressed decays $D^{+}\to \ddot{I}‰\ddot{I}{€}^{+}$ and $D^0\to \ddot{I}‰\ddot{I}{€}^0$. A double tag technique is used to measure the absolute branching fractions $\mathcal{B}(D^{+}\to \ddot{I}‰\ddot{I}{€}^{+})=(2.79\pm 0.57\pm 0.16)\times 10^{-4}$ and $\mathcal{B}(D^0\to \ddot{I}‰\ddot{I}{€}^0)=(1.17\pm 0.34\pm 0.07)\times 10^{-4}$, with statistical significances of $5.5\ddot{I}ƒ$ and $4.1\ddot{I}ƒ$, respectively. We also present measurements of the absolute branching fractions for the related $\hat{I}\cdot \ddot{I}€$ decay modes. We find $\mathcal{B}(D^{+}\to \hat{I}\cdot \ddot{I}{€}^{+})=(3.07\pm 0.22\pm 0.13)\times 10^{-3}$ and $\mathcal{B}(D^0\to \hat{I}\cdot \ddot{I}{€}^0)=(0.65\pm 0.09\pm 0.04)\times 10^{-3}$, which are consistent with the current world averages. The first and second uncertainties are statistical and systematic, respectively.