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Nuclear Physics Seminars

ics Nuclear
Tuesday, March 25, 2014
3:30 PM
Physics Building, Room 204
David Flay [Host: Xiaochao Zheng]
Temple University
"Preliminary Results for Measurements of the Lorentz Color Force d2 and the Longitudinal Spin Asymmetry A1 on the Neutron"
The quantity d2, written as an x2-weighted moment of a linear combination of the spin structure functions g1 and g2, 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 di-quark system. It has been calculated in diff erent nucleon structure models and in lattice QCD, where it is seen to be small and negative for Q2 > 4 GeV2. The existing measurement for the matrix element d2 on the neutron from the combined data of SLAC E155 and Jeff erson Lab E99-117 at Q2 = 5 GeV2 disagrees with the lattice QCD calculation by almost two standard deviations. This discrepancy served as the motivation for the E06-014 experiment in Hall A of Je fferson Lab. Double-spin 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 3He target, covering the DIS and resonance regions characterized by 0:25 < x < 0:90 and 2 ≤ Q2 ≤ 7 GeV2. This allowed for the extraction of dn2 matrix element in two ⟨Q2⟩ bins of 3.21 and 4.32 GeV2. Additionally, the virtual photon-nucleon asymmetry An1 was extracted, along with the evaluation of the polarized-to-unpolarized quark ratios Δu ⁄ u and Δd ⁄ d. The matrix element a2 is also obtained from our g1 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 dn2 and An1 with the upgrade of Je fferson Lab will be discussed.

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