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Article
Gluon-Spin Contribution to the Proton Spin from the Double-Helicity Asymmetry in Inclusive pi(0) Production in Polarized p plus p Collisions at root s=200 GeV
Physical Review Letters
Document Type
Article
Disciplines
Publication Version
Published Version
Publication Date
7-3-2009
DOI
10.1103/PhysRevLett.103.012003
Abstract
The double helicity asymmetry in neutral pion production for p(T) = 1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, Delta G, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of mu 2 = 4 GeV2 a next to leading order QCD analysis gives Delta G([0.02,0.3]) = 0.2, with a constraint of -0.7 < Delta G([0.02,0.3]) < 0.5 at Delta chi(2) = 9 (similar to 3 sigma) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the Delta G constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.
Copyright Owner
American Physical Society
Copyright Date
2009
Language
en
File Format
application/pdf
Citation Information
Andrew Adare, John C. Hill, Todd Kempel, John G. Lajoie, et al.. "Gluon-Spin Contribution to the Proton Spin from the Double-Helicity Asymmetry in Inclusive pi(0) Production in Polarized p plus p Collisions at root s=200 GeV" Physical Review Letters Vol. 103 Iss. 1 (2009) p. 012003 Available at: http://works.bepress.com/craig-ogilvie/158/
This article is published as Adare, Andrew, Sergey Afanasiev, Christine Aidala, N. N. Ajitanand, Yasuyuki Akiba, H. Al-Bataineh, John Alexander et al. "Gluon-Spin Contribution to the Proton Spin from the Double-Helicity Asymmetry in Inclusive π 0 Production in Polarized p+ p Collisions at s= 200 GeV." Physical review letters 103, no. 1 (2009): 012003. DOI:10.1103/PhysRevLett.103.012003. Posted with permission.