Nuclear Medium Effects in $J/\Psi$ Production at HERA-B
  In this paper we estimate the influence of the shadowing effect and initial state parton energy loss in the quarkonium production at HERA-B. We analyze the $x_F$ behavior of the effective exponent $\alpha (x_F)$ and present a comparison with the preliminary HERA-B data for $J/\Psi$ production. Moreover, we estimate the magnitude of these effects in the $J/\Psi$ production at RHIC. 
A. L. Ayala Filho, C. Brenner Mariotto, V. P. Goncalves