Nuclear modification factors of phi mesons in d plus Au, Cu plus Cu, and Au plus Au collisions at root s(NN)=200 GeV
2011
The PHENIX experiment at the
Relativistic Heavy Ion Colliderhas performed systematic measurements of
phi mesonproduction in the K+K- decay channel at midrapidity in p + p, d + Au, Cu + Cu, and Au + Au
collisionsat root 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 midcentral Au + Au
collisions, the R-AA of phi exhibits a suppression relative to expectations from
binary scaledp + p results. The amount of suppression is smaller than that of the pi(0) and the. in the intermediate p(T) range (2-5 GeV/c), whereas, at higher p(T), the phi, pi(0), and. show similar suppression. The baryon (proton and
antiproton) excess observed in central Au + Au
collisionsat intermediate p(T) is not observed for the
phi mesondespite the similar masses of the proton and the phi. This suggests that the excess is linked to the number of valence quarks in the hadron rather than its mass. The difference gradually disappears with decreasing centrality, and, for peripheral
collisions, the R-AA values for both particle species are consistent with
binary scaling. Cu + Cu
collisionsshow the same yield and suppression as Au + Au
collisionsfor the same number of N-part. The R-dA of phi shows no evidence for cold nuclear effects within uncertainties.
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