Baryonic D decay Ds+→pn¯ and its implication

The channel Ds+→pn¯ 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 Ds+ decay, where the latter can be obtained from the analysis of the diagrammatic approach, we find that Ds+→pn¯ becomes visible. The observation of this baryonic D decay implies the dynamical enhancement of the W-annihilation topology in the Ds+ decay.