Gluon-Spin Contribution to the Proton Spin from the Double-Helicity Asymmetry in Inclusive pi{sup 0} Production in Polarized p+p Collisions at sq root(s)=200 GeV

Journal Article · Fri Jul 03 04:00:00 EDT 2009 · Physical Review Letters

DOI:https://doi.org/10.1103/PHYSREVLETT.103.012003· OSTI ID:21347016

Adare, A; Bickley, A A; Ellinghaus, F; Glenn, A; Kinney, E; Kiriluk, K; Nagle, J L; Seele, J; Wysocki, M ^[1]; Afanasiev, S; Isupov, A; Litvinenko, A; Malakhov, A; Peresedov, V; Rukoyatkin, P; Zolin, L ^[2]; Aidala, C ^[3]; Ajitanand, N N; Alexander, J; Chung, P ^[4]

---

1. University of Colorado, Boulder, Colorado 80309 (United States)
2. Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation)
3. Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003-9337 (United States)
4. Chemistry Department, Stony Brook University, Stony Brook, SUNY, New York 11794-3400 (United States)

The double helicity asymmetry in neutral pion production for p{sub T}=1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, DELTAG, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of mu{sup 2}=4 GeV{sup 2} a next to leading order QCD analysis gives DELTAG{sup [0.02,0.3]}=0.2, with a constraint of -0.7<DELTAG{sup [0.02,0.3]}<0.5 at DELTAchi{sup 2}=9 (approx3sigma) 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 DELTAG constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.

• OSTI ID: 21347016
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 1 Vol. 103; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANGULAR MOMENTUM
ASYMMETRY
BARYON-BARYON INTERACTIONS
BARYONS
BOSONS
DEEP INELASTIC SCATTERING
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
FIELD THEORIES
GEV RANGE
GEV RANGE 100-1000
GLUONS
HADRON-HADRON INTERACTIONS
HADRONS
HELICITY
INELASTIC SCATTERING
INTERACTIONS
LEPTON-BARYON INTERACTIONS
LEPTON-HADRON INTERACTIONS
LEPTON-NUCLEON INTERACTIONS
MESONS
NUCLEON-NUCLEON INTERACTIONS
NUCLEONS
PARTICLE INTERACTIONS
PARTICLE PROPERTIES
PIONS
PIONS NEUTRAL
PROTON-NUCLEON INTERACTIONS
PROTON-PROTON INTERACTIONS
PROTONS
PSEUDOSCALAR MESONS
QUANTUM CHROMODYNAMICS
QUANTUM FIELD THEORY
SCATTERING
SPIN