"Preliminary Results for Measurements of the Lorentz Color Force d_{2} and the Longitudinal Spin Asymmetry A_{1} on the Neutron"David Flay , Temple University [Host: Xiaochao Zheng]
ABSTRACT:
The quantity d_{2}, written as an x^{2}weighted moment of a linear combination of the spin structure functions g_{1} and g_{2}, has the interpretation of being the average transverse Lorentz color force felt by a quark immediately following its interaction with a virtual photon in the deep inelastic scattering (DIS) process due to the remnant diquark
system. It has been calculated in different nucleon structure models and in lattice QCD, where it is seen to be small and negative for Q^{2} > 4 GeV^{2}. The existing measurement for the matrix element d_{2} on the neutron from the combined data of SLAC E155 and Jefferson Lab E99117 at Q^{2} = 5 GeV^{2} disagrees with the lattice QCD calculation by almost two standard deviations. This discrepancy served as the motivation for the E06014 experiment in Hall A of Jefferson Lab. Doublespin asymmetries and unpolarized cross sections were measured in the scattering of a longitudinally polarized electron beam of energies 4.74 and 5.89 GeV from a longitudinally and transversely polarized ^{3}He target, covering the DIS and resonance regions characterized by 0:25 < x < 0:90
and 2 ≤ Q^{2} ≤ 7 GeV^{2}. This allowed for the extraction of d^{n}_{2} matrix element in two ⟨Q^{2}⟩ bins of 3.21 and 4.32 GeV^{2}. Additionally, the virtual photonnucleon asymmetry A^{n}_{1}
was extracted, along with the evaluation of the polarizedtounpolarized quark ratios
Δu ⁄ u and Δd ⁄ d. The matrix element a_{2} is also obtained from our g_{1} data. We present the results of our measurements, which are compared to the world data and various theoretical models and lattice QCD calculations. Future plans to measure d^{n}_{2} and A^{n}_{1} with the upgrade of Jefferson Lab will be discussed.

Nuclear Physics Seminar Tuesday, March 25, 2014 3:30 PM Physics Building, Room 204 Note special room. 
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