Associative charm photoproduction with circularly polarized photons
  We calculate the asymmetries for the processes $\vec\gamma+\vec p\to \Lambda_c^+ (\Sigma_c^+)+\bar{D^0}$ and $\vec\gamma+\vec p\to \Lambda_c^+ (\Sigma_c^+)+\bar{D^*}$, induced by circularly polarized photons on a polarized proton target in the framework of an effective Lagrangian model. We found large and positive values for the asymmetry induced by the $z-$component of the proton polarization, in a wide energy region, from threshold up to $E_\gamma=70$ GeV. In the case of pseudoscalar meson photoproduction, the predictions are qualitatively model-independent. For $D^*$-photoproduction, there is a strong dependence of the asymmetries on $N\Lambda_c D(D^*)$-coupling constants. 
Michail P. Rekalo and Egle Tomasi-Gustafsson