Physics – Nuclear Physics – Nuclear Experiment
Scientific paper
2004-09-28
AIPConf.Proc.747:83-88,2005
Physics
Nuclear Physics
Nuclear Experiment
6 pages, 2 figures, HiX2004 workshop proceedings
Scientific paper
10.1063/1.1871643
Recent progress from Jefferson Lab has significantly improved our understanding of the nucleon spin structure in the high-$x$ region. Results from two experiments in Hall A are presented. The first experiment is a precision measurement of the neutron spin asymmetry, $A_1^n$, in the high-$x$ (valence quark) region. The results show for the first time that $A_1^n$ becomes positive at large $x$, strongly breaking SU(6) (spin-flavor) symmetry. The data trend is in good agreement with SU(6)-breaking valence quark models and with the fits to the previous world data. Combining the $A_1^n$ results with the world $A_1^p$ data, the up and down quark spins distributions in the nucleon were extracted. The results showed that for the proton the valence down quark spin is in the opposite direction from that of the proton, in disagreement with predictions of leading-order perturbative QCD models, which neglect quark orbital angular momentum. In the second experiment, the $Q^2$ dependence of the moments and sum rules of the spin structure in the low to intermediate $Q^2$ region were measured, providing a unique bridge linking the quark-gluon picture of the nucleon and the coherent hadronic picture.
JLab Hall A.
Chen E94-010 Collaborations: J. P.
No associations
LandOfFree
Neutron Spin Structure Measurements in JLab Hall A does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Neutron Spin Structure Measurements in JLab Hall A, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Neutron Spin Structure Measurements in JLab Hall A will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-531092