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

J /ψ production has been measured in Au+Au and Cu+Cu collisions at by the PHENIX experiment at the relativistic heavy ion collider (RHIC) during 2004 and 2005, respectively, at mid-rapidity (|η|⩽ 0.35) via J /ψ → e + e − decay and at forward rapidity (1.2 ⩽|η|⩽ 2.2) via J /ψ → μ + μ − decay. The nuclear modification factor ( R AA ) of J /ψ 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.