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Measurement of the x- and Q2-dependence of the asymmetry A1 on the nucleon
- Source :
- Physics Letters B. 641:11-17
- Publication Year :
- 2006
- Publisher :
- Elsevier BV, 2006.
-
Abstract
- We report results for the virtual photon asymmetry A{sub 1} on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton ({sup 15}NH{sub 3}) and deuteron ({sup 15}ND{sub 3}) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present paper, we concentrate on our results for A{sub 1}(x,Q{sup 2}) and the related ratio g{sub 1}/F{sub 1}(x,Q{sup 2}) in the resonance and the deep inelastic regions for our lowest and highest beam energies, covering a range in momentum transfer Q{sup 2} from 0.05 to 5.0 GeV{sup 2} and in final-state invariant mass W up to about 3 GeV. Our data show detailed structure in the resonance region, which leads to a strong Q{sup 2}--dependence of A{sub 1}(x,Q{sup 2}) for W below 2 GeV. At higher W, a smooth approach to the scaling limit, established by earlier experiments, can be seen, but A{sub 1}(x,Q{sup 2}) is not strictly Q{sup 2}--independent. We add significantly to the world data set at high x, up to x = 0.6. Our data exceed the SU(6)-symmetric quark model expectation for both the proton and the deuteron whilemore » being consistent with a negative d-quark polarization up to our highest x. This data set should improve next-to-leading order (NLO) pQCD fits of the parton polarization distributions.« less
- Subjects :
- Quark
Physics
Nuclear and High Energy Physics
Particle physics
Proton
010308 nuclear & particles physics
media_common.quotation_subject
Momentum transfer
Quark model
Parton
01 natural sciences
Asymmetry
Nuclear physics
0103 physical sciences
Invariant mass
010306 general physics
Nucleon
media_common
Subjects
Details
- ISSN :
- 03702693
- Volume :
- 641
- Database :
- OpenAIRE
- Journal :
- Physics Letters B
- Accession number :
- edsair.doi...........4fda3011bd149498b6b07a0f69e279ed