Influence of system size dependence of energy loss on hadron spectra suppression

Based on parton model in QCD, at the leading-order approximation we studied the π0 spectra and nuclear modification factor RAA in Au + Au and Cu + Cu collisions with different centralities. Because of parton jet energy loss in heavy ion collision, large transverse momentum hadrons spectra are suppressed as compared to p + p collisions at the same energy. It is shown that the suppression has strong dependence on the system size which determines the amount of the jet energy loss. The bigger the system is, the larger parton energy loss is. It results in the much more suppression of the spectra and also the much less RAA. (authors)