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
Contribuinte(s) |
UNIVERSIDADE DE SÃO PAULO |
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Data(s) |
18/04/2012
18/04/2012
2009
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Resumo |
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 GeV(2) 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. Office of Nuclear Physics in DOE Office of Science National Science Foundation NSF Renaissance Technologies (U.S.) MEXT and JSPS (Japan) CNPq and FAPESP (Brazil) NSFC (China) MSMT (Czech Republic) Centre National de la Recherche Scientifique - IN2P3/CNRS and CEA (France) BMBF - Bundesministerium fur Bildung und Forschung, (DAAD) Deutscher Akademischer Austausch Dienst, and Alexander von Humboldt Foundation (Germany) OTKA (Hungary) (DAE) Department of Atomic Energy, India ISF - Israel Science Foundation (Israel) KRF and KOSEF (Korea) MES Ministry of Education and Science of the Russian Federation, RAS Russia Academy of Sciences, and FAAE (Russia) U. S. CRDF for the FSU U.S.-Hungary Fulbright (BSF) US-Israel Binational Science Foundation |
Identificador |
PHYSICAL REVIEW LETTERS, v.103, n.1, 2009 0031-9007 http://producao.usp.br/handle/BDPI/16096 10.1103/PhysRevLett.103.012003 |
Idioma(s) |
eng |
Publicador |
AMER PHYSICAL SOC |
Relação |
Physical Review Letters |
Direitos |
restrictedAccess Copyright AMER PHYSICAL SOC |
Palavras-Chave | #PARTON DISTRIBUTIONS #Physics, Multidisciplinary |
Tipo |
article original article publishedVersion |