Physical Review Letters 97,15 (2006) 152302;
Measurements of the production of forward pi(0) mesons from p+p and d+Au collisions at root 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 similar to 30% of the p+p yield at =4.00, well below shadowing expectations. Exploratory measurements of azimuthal correlations of the forward pi(0) with charged hadrons at eta approximate to 0 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.
proton-nucleus collisions;; color glass condensate;; gluon distribution;; ep scattering;; qcd;; fragmentation;; pp
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