PHENIX results on the $\sqrt{s_\mathrm{NN}}$ dependence of jet quenching

The PHENIX experiment has established jet quenching at a center-of-mass energy of 200 GeV in Au+Au collisions. Recent measurements of Cu+Cu collisions at the same center-of-mass energy support a parton energy loss scenario. Furthermore, the onset of jet quenching was studied in Cu+Cu collisions for three center-of-mass energies 22.4, 62.4 and 200 GeV.