  Nuclear modification factors for pion production in AuAu and CuCu collisions
are analyzed at very high transverse momenta. At p_T > 10 GeV/c, the
R_{AA}(p_T) is determined mostly by the initial state nuclear modifications
(e.g. EMC effect) and the non-Abelian jet-energy loss in the final state. At
high momenta these effects together are strong enough to suppress R_{AA}(p_T)
to below 1 at RHIC energies. We display results using HKN shadowing in our pQCD
improved parton model. Result of a similar calculation at LHC energies for PbPb
collisions are also displayed. Based on dN/dy estimates, a larger opacity
value, L/\lambda_g = 10 +/- 2, is used for the produced partonic matter in
central collisions at the LHC.
