Threshold open charm production in nucleon-nucleon collisions
  The associative charm particles production in nucleon-nucleon collisions $N+N\to \Lambda_c(\Sigma_c)+\bar{D}+N$, is described in a general way and the spin and isospin structure of the corresponding matrix elements are derived. Using an analogy with strange particle ($\Lambda K$)-production, the $D-$meson exchange model is considered in detail. Estimations of the energy behavior of the threshold cross sections show a large dependence on the form of the phenomenological hadron form factors and indicate that, at threshold, the cross section is three order of magnitude smaller than for strange particle production. 
Michail P. Rekalo Egle Tomasi-Gustafsson