"Figure 1" of "Forward neutral pion production in p+p and d+Au collisions at s(NN)**(1/2) = 200-GeV."

Measurements of the production of forward $\pi^{0}$ mesons from p+p and d+Au collisions at $\sqrt{s_{NN}}$= 200 GeV are reported. The p+p yield generally agrees with next-to-leading order perturbative QCD calculations. The d+Au yield per binary collision is suppressed as $\eta$ increases, decreasing to ~30% of the p+p yield at $\langle\eta\rangle$= 4.00, well below shadowing expectations. Exploratory measurements of azimuthal correlations of the forward $\pi^{0}$ with charged hadrons at $\eta\approx0$ show a recoil peak in p+p that is suppressed in d+Au at low pion energy. These observations are qualitatively consistent with a saturation picture of the low-x gluon structure of heavy nuclei.