Nuclear Physics Seminar

Jefferson Lab experiment E06-014, performed in Hall A, made measurements of the double-spin asymmetries and absolute cross sections in both the DIS and resonance regions by scattering longitudinally polarized electrons at beam energies of 4.74 and 5.89 GeV from a longitudinally and transversely polarized 3He target. Through these measurements various aspects of the neutron spin structure were investigated. The g2 nucleon spin-dependent structure function contains information beyond the simple parton model description of the nucleon. It provides insight into quark-gluon correlations and a path to access the confining local color force a struck quark experiences just as it is hit by the virtual photon due to the remnant di-quark. The quantity d2, a measure of this local color force, has its information encoded in an x2 weighted integral of a linear combination of spin structure functions g1 and g2 and thus is dominated by the valence-quark region at large momentum fraction x. To date, theoretical calculations and experimental measurements of the neutron d2 differ by about two standard deviations. Therefore E06-014 made a precision measurement of this quantity. The polarized quark distributions were also investigated through measurements of the virtual photon-nucleon asymmetry A1^n, the structure function ratio g1/F1, and quark ratio (delta d+delta d_bar)/(d+d_bar). The E06-014 results for the spin structure functions (g1,g2) on 3He, dn2, An1, (delta d+delta d_bar)/(d+d_bar), and our extractions of the neutron color electric and magnetic forces will be presented.