Observation of the $W$-Annihilation Decay $D^{+}_{s} \rightarrow ω π^{+}$ and Evidence for $D^{+}_{s} \rightarrow ωK^{+}$

Abstract: We report on the observation of the $W$-annihilation decay $D^{+}_{s} \rightarrow \omega \pi<sup>{+}$ and the evidence for $D_{s}^{+} \rightarrow \omega K<sup>{+}$ with a data sample corresponding to an integrated luminosity of 3.19 fb$<sup>{-1}$ collected with the BESIII detector at the center-of-mass energy $\sqrt{s} = 4.178$ GeV. We obtain the branching fractions $$\mathcal{B}(D^{+}_{s} \rightarrow \omega \pi^{+}) = (1.77\pm0.32_{{\rm stat.}}\pm0.11_{{\rm sys.}}) \times 10<sup>{-3}$$ and $$\mathcal{B}(D^{+}_{s} \rightarrow \omega K^{+}) = (0.87\pm0.24_{{\rm stat.}}\pm0.07_{{\rm sys.}}) \times 10<sup>{-3}$$, respectively.