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

The baryonic decay $D_s^{+}\to p\overline{n}$ 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 $3.19{\mathrm{fb}}^{-1}$. The result confirms the previous measurement by the CLEO Collaboration and is of greatly improved precision. This result will improve our understanding of the dynamical enhancement of the $W$-annihilation topology in the charmed meson decays.

Figure 1

Fits to the $M_{\mathrm{tag}}$ distributions for various ST modes. The dots with error bars show data, the red solid lines are the overall fit results, and the blue dashed curves are the background.

Figure 2

Fit to the $M_{\mathrm{miss}}$ distribution. The dots with error bars represent data, the (green) shaded histogram shows the events in the $M_{\mathrm{tag}}$ sideband region. The (red) solid line is the overall fit, the (violet) dotted line is the signal component, and the (blue) dashed line is the background component from the fit.