  The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has
performed systematic measurements of phi meson production in the K+K- decay
channel at midrapidity in p+p, d+Au, Cu+Cu and Au+Au collisions at
sqrt(S_NN)=200 GeV. Results are presented on the phi invariant yield and the
nuclear modification factor R_AA for Au+Au and Cu+Cu, and R_dA for d+Au
collisions, studied as a function of transverse momentum (1<p_T<7 GeV/c) and
centrality. In central and mid-central Au+Au collisions, the R_AA of phi
exhibits a suppression relative to expectations from binary scaled p+p results.
The amount of suppression is smaller than that of the neutral pion and the eta
meson in the intermediate p_T range (2--5 GeV/c); whereas at higher p_T the
phi, pi^0, and eta show similar suppression. The baryon (protons and
anti-protons) excess observed in central Au+Au collisions at intermediate p_T
is not observed for the phi meson despite the similar mass of the proton and
the phi. This suggests that the excess is linked to the number of constituent
quarks rather than the hadron mass. The difference gradually disappears with
decreasing centrality and for peripheral collisions the R_AA values for both
particles are consistent with binary scaling. Cu+Cu collisions show the same
yield and suppression as Au+Au collisions for the same number of N_part. The
R_dA of phi shows no evidence for cold nuclear effects within uncertainties.
