Gluon-Spin contribution to the proton spin from the double-helicity asymmetry in inclusive π0 production in polarized p+p collisions at s=200GeV

PHENIX Collaboration

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100 Scopus citations

Abstract

The double helicity asymmetry in neutral pion production for pT=1 to 12GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, ΔG, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of μ2=4GeV2 a next to leading order QCD analysis gives ΔG[0.02,0.3]=0.2, with a constraint of -0.7<ΔG[0. 02,0.3]<0.5 at Δχ2=9 (∼3σ) 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 ΔG constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.

Original languageEnglish
Article number012003
JournalPhysical Review Letters
Volume103
Issue number1
DOIs
StatePublished - 6 Aug 2009
Externally publishedYes

ASJC Scopus subject areas

  • General Physics and Astronomy

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