Centrality dependence of J/Psi production in Au+Au and Cu+Cu collisions by the PHENIX experiment at RHIC.

J/{psi} production has been measured in Au+Au and Cu+Cu at {radical}(s{sub NN})=200 GeV by the PHENIX experiment at the relativistic heavy ion collider (RHIC) during 2004 and 2005, respectively, at mid-rapidity (|{eta}|{le} 0.35) via J/{psi} {yields} e{sup +}e{sup -} decay and at forward rapidity (1.2 {le}|{eta}|{le} 2.2) via J/{psi} {yields} {mu}{sup +}{mu}{sup -} decay. The nuclear modification factor (RAA) of J/{psi} is presented as a function of the collision centrality for Au+Au collisions (final results) and Cu+Cu collisions (preliminary results) in both rapidity windows. These results are compared to SPS results at lower energy and to various theoretical calculations.