Measurements of J/$ψ$ yields at forward and mid-rapidity in d+Au, Cu+Cu and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV by PHENIX at RHIC

Abstract

The J/$ψ$ yields in heavy ion collisions are expected to be a promising probe of deconfined matter, since theoretical models predict that the J/$ψ$ production could be strongly suppressed due to color screening effect in a Quark Gluon Plasma. In addition, one of the interesting predictions that has emerged recently is the J/$ψ$ enhancement at RHIC energy via competing mechanisms such as recombination. The PHENIX collaboration has measured J/$ψ$ production via its decay into lepton pairs in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}$ = 200 GeV. The nuclear modification factor $R_{\rm AA}$ for the ${\rm J}/ψ$ is obtained by comparing Au+Au or Cu+Cu collisions to p+p collisions. The $R_{\rm AA}$ dependences on centrality, transverse momentum and rapidity are presented both at forward rapidity ($1.2<|y|<2.2$) using ${\rm J}/ψ\toμ^+μ^-$ and at mid rapidity ($|y|<0.35$) using ${\rm J}/ψ\to e^+e^-$. These preliminary results are compared to cold nuclear matter expectations derived from PHENIX d+Au measurements, to results obtained by NA50 experiment and to various theoretical models.