J/ψ production in Au+Au and Cu+Cu collisions at at STAR

J/ψ production is considered to be a sensitive probe of the properties of quark gluon plasma created in nucleus+nucleus collisions at RHIC. In this article, the recent analysis of mid-rapidity (|y|<1) J/ψ production via the dielectron decay channel in Au+Au (year 2007) and Cu+Cu (year 2005) collisions at at STAR is reported. It is compared to STAR p+p results in order to study the nuclear modification factor as a function of transverse momentum and centrality. The results are compared to previously published data and available theoretical models.