Observations of the Cabibbo-Suppressed decays $\hat{I}{›}_c^{+}\to n\ddot{I}{€}^{+}\ddot{I}{€}^0$, $n\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}$ and the Cabibbo-Favored decay $\hat{I}{›}_c^{+}\to n{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{+}$

Abstract

Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 ${\mathrm{fb}}^{-1}$, collected by the BESIII detector in the energy region between $4600$ MeV and $4699$ MeV, we report the first observations of the Cabibbo-suppressed decays $\hat{I}{›}_c^{+}\to n\ddot{I}{€}^{+}\ddot{I}{€}^0$, $\hat{I}{›}_c^{+}\to n\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}$, and the Cabibbo-favored decay $\hat{I}{›}_c^{+}\to n{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{+}$ with statistical significances of $7.9\ddot{I}ƒ$, $7.8\ddot{I}ƒ$, and $>10\ddot{I}ƒ$, respectively. The branching fractions of these decays are measured to be $\mathcal{B}(\hat{I}{›}_c^{+}\to n\ddot{I}{€}^{+}\ddot{I}{€}^0)=(0.64\pm 0.09\pm 0.02)\%$, $\mathcal{B}(\hat{I}{›}_c^{+}\to n\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+})=(0.45\pm 0.07\pm 0.03)\%$, and $\mathcal{B}(\hat{I}{›}_c^{+}\to n{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{+})=(1.90\pm 0.08\pm 0.09)\%$, where the first uncertainties are statistical and the second are systematic. We find that the branching fraction of the decay $\hat{I}{›}_c^{+}\to n\ddot{I}{€}^{+}\ddot{I}{€}^0$ is about one order of magnitude higher than that of $\hat{I}{›}_c^{+}\to n\ddot{I}{€}^{+}$.