φ Meson production in the forward/backward rapidity region in Cu + Au collisions at s NN =200 GeV

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured φ meson production and its nuclear modification in asymmetric Cu+Au heavy-ion collisions at sNN=200 GeV at both forward Cu-going direction (1.2<y<2.2) and backward Au-going direction (-2.2<y<-1.2) rapidities. The measurements are performed via the dimuon decay channel and reported as a function of the number of participating nucleons, rapidity, and transverse momentum. In the most central events, 0%-20% centrality, the φ meson yield integrated over 1<pT<5 GeV/c prefers a smaller value, which means a larger nuclear modification, in the Cu-going direction compared to the Au-going direction. Additionally, the nuclear-modification factor in Cu+Au collisions averaged over all centrality is measured to be similar to the previous PHENIX result in d+Au collisions for these rapidities.