Campus Units

Physics and Astronomy

Document Type

Article

Publication Version

Published Version

Publication Date

7-3-2009

Journal or Book Title

Physical Review Letters

Volume

103

Issue

1

First Page

012003

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.

Comments

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.

Copyright Owner

American Physical Society

Language

en

File Format

application/pdf

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