High pT suppression vs system size and energy

High pT particles probe the medium created in nucleus-nucleus collisions. The high pT partons will suffer jet quenching in the medium before it hadronizes. The number of high pT partons is proportional to the number of hard scatterings in the collision. Indirect measurement of the energy loss (relative to the number of hard scatterings) of the partons can be studied in the nuclear modification factor, RAA. Studying the RAA as a function of collision energy, rapidity and system size will constrain models that try to describe these collisions. Here we will present nuclear modification factors from Au-Au and Cu-Cu collisions at and compare these with Au-Au collisions at .