Highlights and Perspectives of the JLab Spin Physics Program
arXiv:0804.4486 · doi:10.1140/epjst/e2008-00782-y
Abstract
Nucleon spin structure has been an active and exciting subject of interest for the last three decades. Recent precision spin-structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure in the valence quark (high-x) region and improved our understanding of higher-twist effects, spin sum rules and quark-hadron duality. First, results of spin sum rules and polarizabilities in the low to intermediate Q^2 region are presented. Comparison with theoretical calculations are discussed. Surprising disagreements of Chiral Perturbation Theory calculations with experimental results on the generalized spin polarizability, δ_{LT}, were found. Then, precision measurements of the spin asymmetry in the high-x region are presented. They provide crucial input for global fits to world data to extract polarized parton distribution functions. The up and down quark spin distributions in the nucleon were extracted. The results for Δd/d disagree with the leading-order pQCD prediction assuming hadron helicity conservation. Results of precision measurements of the g_2 structure function to study higher-twist effects are presented. The data indicate a significant higher-twist (twist-3 or higher) effect. The second moment of the spin structure functions and the twist-3 matrix element d_2 results were extracted. The high Q^2 result was compared with a Lattice QCD calculation. Results on the resonance spin-structure functions in the intermediate Q^2 range are presented, which, in combination with DIS data, enable a detailed study of quark-hadron duality in spin-structure functions. Finally, an experiment to study neutron transversity and transverse spin asymmetries is discussed. A future plan with the 12 GeV energy upgrade at JLab is briefly outlined.
15 pages, 8 figures, to be published in Proceedings of Prague-Spin2007
References in corpus (11)
- Hadronic Spectra and Light-Front Wavefunctions in Holographic QCD
- Precise determination of the spin structure function of the proton, deuteron and neutron
- A new measurement of the Collins and Sivers asymmetries on a transversely polarised deuteron target
- Measurement of the - and -Dependence of the Asymmetry on the Nucleon
- Determination of the effective strong coupling constant alpha_{s,g_1}(Q^2) from CLAS spin structure function data
- Experimental study of isovector spin sum rules
- Effect of Orbital Angular Momentum on Valence-Quark Helicity Distributions
- Moments of the Spin Structure Functions g_1^p and g_1^d for 0.05 < Q^2 < 3.0 GeV^2
- Proton Spin Structure in the Resonance Region
- Quark-Hadron Duality in Neutron (3He) Spin Structure
- 3He Spin-Dependent Cross Sections and Sum Rules