Energy and System Size Dependence of Charged Hadron Transverse Momentum   Spectra from Cu+Cu and Au+Au Collisions at sqrt(s_(NN)) = 62.4 and 200 GeV
  The PHOBOS collaboration has measured transverse momentum distributions of charged hadrons produced in Cu+Cu collisions at sqrt(s_(NN)) = 200 and 62.4 GeV. The nuclear modification factor R_(AA)^(Npart) is calculated relative to p+p data at both collision energies as a function of collision centrality. For the same number of participating nucleons, R_(AA)^(Npart) is essentially the same in both systems over the full range of p_(T) that is measured. In addition, we observe that within experimental uncertainties, the ratio of 200 GeV to 62.4 GeV Cu+Cu yields has only a moderate centrality dependence and is consistent with the value previously measured in Au+Au collisions for a broad range of p_(T). 
Edward Wenger (for the PHOBOS collaboration)