Measurements of high-pT neutral mesons in $\sqrt{s_{NN}}$ = 200 GeV   Au+Au and Cu+Cu Collisions at RHIC-PHENIX
  Measurements from the RHIC experiments show strong suppression of high-pT hadrons in central Au+Au collisions. The PHENIX experiment has observed strong suppression of $\pi^0$ and charged hadron yields in central Au+Au collisions for pT > 5 GeV/c regardless of pT and particle species. The observed suppression is interpreted in terms of energy loss of quarks in a high-density medium.   The PHENIX Year-4 Au+Au measurements have extended the pT reach of the $\pi^0$ spectra to 20 GeV/c. And the PHENIX Year-5 Cu+Cu measurements performed for the study of particle production in a lighter system and they can provide the system-size dependence of the suppression. The suppression patterns of $\pi^0$/$\eta$ at high pT are presented for each collision system (Au+Au/Cu+Cu). 
Tadaaki Isobe (for the PHENIX Collaboration)