High transverse momentum η meson production in p+p,d+Au, and Au+Au collisions at √s_NN=200 GeV

Abstract

Inclusive transverse momentum spectra of η mesons in the range p_T≈2-12 GeV/c have been measured at midrapidity (|η|<0.35) by the PHENIX experiment at RHIC in p+p,d+Au, and Au+Au collisions at √s_NN=200 GeV. The η mesons are reconstructed through their η→γ γ channel for the three colliding systems as well as through the η→π⁰π⁺π^- 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 η yields are significantly suppressed, with R_AuAu(p_T)≈ 0.2. The ratio of η to π⁰ 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_η/π⁰≈0.5 in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range of center-of-mass energies (√s_NN≈3-1800 GeV) as well as, for high scaled momentum x_p, in e⁺e^- annihilations at √s=91.2 GeV. These results are consistent with a scenario where high-p_T η production in nuclear collisions at the Relativistic Heavy Ion Collider is largely unaffected by initial-state effects but where light-quark mesons (π⁰,η) are equally suppressed due to final-state interactions of the parent partons in the dense medium produced in Au+Au reactions.