  Inclusive transverse momentum spectra of eta mesons in the range p_T~2-12
GeV/c have been measured at mid-rapidity (|\eta| < 0,35) by the PHENIX
experiment at RHIC in p+p, d+Au and Au+Au collisions at sqrt(s_NN) = 200 GeV.
The eta mesons are reconstructed through their eta--> \gamma\gamma channel for
the three colliding systems as well as through the eta-->pi^0 pi+ pi- decay
mode in p+p and d+Au collisions. The nuclear modification factor in d+Au
collisions, R_dAu(p_T~1.0-1.1, suggests at most only modest p_T broadening
("Cronin enhancement"). In central Au+Au reactions, the eta yields are
significantly suppressed, with R_AuAu(pT)~0.2. The ratio of eta to pi^0 yields
is approximately constant as a function of p_T for the three colliding systems
in agreement with the high-p_T world average of R_eta/pi^0 \approx 0.5 in
hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range
of center-of-mass energies [sqrt(s_NN)~3-1800 GeV] as well as, for high scaled
momentum x_p, in e+e- annihilations at sqrt(s)=91.2 GeV. These results are
consistent with a scenario where high-p_T eta production in nuclear collisions
at RHIC is largely unaffected by initial-state effects, but where light-quark
mesons (pi^0;eta) are equally suppressed due to final-state interactions of the
parent partons in the dense medium produced in Au+Au reactions.

Nuclear Experiment