Observation of the $W$-Annihilation Decay $D_s^{+}\to \ddot{I}‰\ddot{I}{€}^{+}$ and Evidence for $D_s^{+}\to \ddot{I}‰K^{+}$

Abstract

We report on the observation of the $W$-annihilation decay $D_s^{+}\to \ddot{I}‰\ddot{I}{€}^{+}$ and the evidence for $D_s^{+}\to \ddot{I}‰K^{+}$ with a data sample corresponding to an integrated luminosity of 3.19 fb${}^{-1}$ collected with the BESIII detector at the center-of-mass energy $\sqrt{s}=4.178$ GeV. We obtain the branching fractions $\mathcal{B}(D_s^{+}\to \ddot{I}‰\ddot{I}{€}^{+})=(1.77\pm 0.32_{stat.}\pm 0.11_{sys.})\times 10^{-3}$ and $\mathcal{B}(D_s^{+}\to \ddot{I}‰K^{+})=(0.87\pm 0.24_{stat.}\pm 0.07_{sys.})\times 10^{-3}$, respectively.