Forward Neutral Pion Production in p + p and d + Au Collisions at √s_(NN) = 200 GeV

Creators: Adams, J.; Hughes, E. W.; Shao, W.; Wang, G.; STAR Collaboration

Abstract

Measurements of the production of forward π^0 mesons from p + p and d + Au collisions at √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 η increases, decreasing to ~30% of the p + p yield at <η> =4.00, well below shadowing expectations. Exploratory measurements of azimuthal correlations of the forward π^0 with charged hadrons at η ≈ 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.

Additional Information

© 2006 American Physical Society. Received 9 February 2006; published 11 October 2006. We thank the RHIC Operations Group and RCF at BNL, and the NERSC Center at LBNL for their support. This work was supported in part by the HENP Divisions of the Office of Science of the US DOE; the US NSF; the BMBF of Germany; IN2P3, RA, RPL, and EMN of France; EPSRC of the United Kingdom; FAPESP of Brazil; the Russian Ministry of Science and Technology; the Ministry of Education and the NNSFC of China; IRP and GA of the Czech Republic, FOM of the Netherlands, DAE, DST, and CSIR of the Government of India; Swiss NSF; the Polish State Committee for Scientific Research; STAA of Slovakia, and the Korea Science and Engineering Foundation. Support of the RBRC for one of the authors (B. F.) is gratefully acknowledged.

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