Nucleon-Antinucleon Annihilation at the Open Charm Threshold

We discuss the $p\bar{p}$ annihilation into a pair of charmed $D$ mesons not far from the threshold of the reaction. An interesting interference pattern in the differential cross section is predicted to arise from the existence of both $t$-channel charmed-baryon exchange and $s$-channel $\Psi^{''}$ charmonium resonance amplitudes. We argue that the experimental study of this process would provide new and valuable information about the unknown $p\bar{p}\Psi^{''}$ and $\Lambda_c N D$ couplings. These are important to know to solve the long-standing puzzle of the heavy flavour contents of baryons and to test the semi-local duality.