Gluon-spin contribution to the proton spin from the double helicity asymmetry in inclusive pi0 production in polarized p + p collisions at s**(1/2) = 200 GeV

0345166 - FZÚ 2011 RIV US eng J - Journal Article
Adare, A. - Afanasiev, S. - Aidala, C. - Růžička, Pavel - Tomášek, Lukáš - Vrba, Václav
Gluon-spin contribution to the proton spin from the double helicity asymmetry in inclusive pi0 production in polarized p + p collisions at s**(1/2) = 200 GeV.
Physical Review Letters. Roč. 103, č. 1 (2009), 012003/1-012003/4. ISSN 0031-9007. E-ISSN 1079-7114
R&D Projects: GA MŠMT LA08015
Institutional research plan: CEZ:AV0Z10100502
Keywords : PHENIX * gluon * proton spin
Subject RIV: BF - Elementary Particles and High Energy Physics
Impact factor: 7.328, year: 2009
http://arxiv.org/pdf/0810.0694

he double helicity asymmetry in neutral pion production for p_T = 1 to 12 GeV/c has been measured with the PHENIX experiment in order 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 GeV^2 give Delta-G^[0.02,0.3] = 0.1 to 0.2, with a constraint of -0.7 < Delta-G^[0.02,0.3] < 0.5 at Delta-chi^2 = 9 (~3 sigma) for our sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for our 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 theoretical scale, a dominant uncertainty in these predictions.
Permanent Link: http://hdl.handle.net/11104/0186495