Baryonic D Decay $D_s^+\to p\bar n$ and Its Implication

TL;DR

This paper discusses the rare baryonic decay of the $D_s^+$ meson into a proton and antineutron, exploring how long-distance effects can enhance its branching ratio and what this reveals about W-annihilation dynamics.

Contribution

It proposes that long-distance contributions significantly enhance the $D_s^+ o par n$ decay, indicating dynamical W-annihilation enhancement in baryonic D decays.

Findings

Long-distance effects can increase the decay rate to observable levels.

Observation implies W-annihilation is dynamically enhanced.

Decay provides insight into baryonic decay mechanisms.

Abstract

The channel $D_s^+\to p\bar n$ is the only kinematically allowed baryonic D decay. It proceeds solely through the W-annihilation topology. Hence, a recent observation of this mode by CLEO will shed light on the dynamics of W-annihilation. At the short-distance level, its branching ratio is very small, of order $10^{-6}$, owing to chiral suppression. It receives long-distance contributions through final-state scattering of the leading tree and color-suppressed amplitudes. Assuming that the long-distance enhancement of W-annihilation in the baryonic D decay is similar to that in the mesonic $D_s^+$ decay, where the latter can be obtained from the analysis of the diagrammatic approach, we find that $D_s^+\to p\bar n$ becomes visible. The observation of this baryonic D decay implies the dynamical enhancement of the W-annihilation topology in the $D_s^+$ decay.