Observation of $D_s^{+}\to p\bar{n}$ and confirmation of its large branching fraction

The baryonic decay $D_s^{+}\to p\bar{n}$ is observed, and the corresponding branching fraction is measured to be $(1.21\pm 0.10\pm 0.05)\times {10}^{-3}$, where the first uncertainty is statistical and second systematic. The data sample used in this analysis was collected with the BESIII detector operating at the BEPCII $e^{+}{e}^{-}$ double-ring collider with a center-of-mass energy of 4.178~GeV and an integrated luminosity of 3.19~fb${}^{-1}$. The result confirms the previous measurement by the CLEO Collaboration and is of greatly improved precision, which may deepen our understanding of the dynamical enhancement of the W-annihilation topology in the charmed meson decays.