Does the $D^-/D^+$ production asymmetry decrease at large $x_F$?
  We have applied the meson cloud model (MCM) to calculate the asymmetries in $D$ and $D_s$ meson production in high energy $\Sigma^-$-nucleus and $\pi^-$-nucleus collisions. We find a good agreement with recent data. Our results suggest that the asymmetries may decrease at large $x_F$. 
F. Carvalho, F.O. Dur\~aes, F.S. Navarra, M. Nielsen