Measurements of d_2^n and A_1^n: Probing the neutron spin structure
Abstract
We report on the results of the E06-014 experiment performed at Jefferson Lab in Hall A, where a precision measurement of the twist-3 matrix element d_2 of the neutron (d^n_2) was conducted. The quantity dn_2 represents the average color Lorentz force a struck quark experiences in a deep inelastic electron scattering event off a neutron due to its interaction with the hadronizing remnants. This color force was determined from a linear combination of the third moments of the ^3He spin structure functions, g_1 and g_2, after nuclear corrections had been applied to these moments. The structure functions were obtained from a measurement of the unpolarized cross section and of double-spin asymmetries in the scattering of a longitudinally polarized electron beam from a transversely and a longitudinally polarized ^3He target. The measurement kinematics included two average Q^2 bins of 3.2 GeV^2 and 4.3 GeV^2, and Bjorken-x 0.25≤ x ≤0.90 covering the deep inelastic and resonance regions. We have found that d^n_2 is small and negative for ⟨Q^2⟩=3.2 GeV^2, and even smaller for ⟨Q^2⟩=4.3 GeV^2, consistent with the results of a lattice QCD calculation. The twist-4 matrix element f^n_2 was extracted by combining our measured d^n_2 with the world data on the first moment in x of g^n_1, Γ^n_1. We found f^n_2 to be roughly an order of magnitude larger than dn2. Utilizing the extracted d^n_2 and f^n_2 data, we separated the Lorentz color force into its electric and magnetic components, F^(y,n)_E and F^(y,n)_B, and found them to be equal and opposite in magnitude, in agreement with the predictions from an instanton model but not with those from QCD sum rules. Furthermore, using the measured double-spin asymmetries, we have extracted the virtual photon-nucleon asymmetry on the neutron A^n_1, the structure function ratio g^n_1/F^n_1, and the quark ratios (Δu+Δu)/(u+u) and (Δd+Δd)/(d+d). These results were found to be consistent with deep-inelastic scattering world data and with the prediction of the constituent quark model but at odds with the perturbative quantum chromodynamics predictions at large x.
Additional Information
© 2016 American Physical Society. Received 13 March 2016; published 6 September 2016. We would like to thank the Jefferson Lab Accelerator Division and Hall A staff for their efforts, which resulted in the successful completion of the experiment. We would also like to thank M. Burkardt, L. Gamberg, W. Melnitchouk, and J. Soffer for theoretical support and useful discussions. This material is based upon work supported by the U.S. Department of Energy (DOE) Office of Science under Awards No. DE-FG02-94ER40844 and No. DE-FG02-87ER40315. Jefferson Lab is operated by the Jefferson Science Associates, LLC, under DOE Grant No. DE-AC05-060R23177.Attached Files
Published - PhysRevD.94.052003.pdf
Submitted - 1603.03612v3.pdf
Supplemental Material - results_asym_He-3.txt
Supplemental Material - results_asym_n.txt
Supplemental Material - results_color-forces.txt
Supplemental Material - results_final-unpol-xs_He-3.txt
Supplemental Material - results_matrix-elements_n.txt
Supplemental Material - results_pol-sf_He-3.txt
Supplemental Material - results_quark-ratios.txt
Supplemental Material - syst-err_A1.txt
Supplemental Material - syst-err_a2.txt
Supplemental Material - syst-err_d2n.txt
Supplemental Material - syst-err_final-asym_He-3.txt
Supplemental Material - syst-err_final-unpol-xs_He-3.txt
Supplemental Material - syst-err_g1F1.txt
Supplemental Material - syst-err_pol-sf_He-3.txt
Supplemental Material - syst-err_quark-ratios.txt
Files
Name | Size | Download all |
---|---|---|
md5:a3311c3b1e30c0f198c796070dfeda60
|
3.8 MB | Preview Download |
md5:9d12b64a72402edd25764b6195fd93a6
|
3.9 kB | Preview Download |
md5:970a0f6cb47ebd0b6d550c7293b9c341
|
659 Bytes | Preview Download |
md5:da3f3c61cb3de17cc250ef034c80779e
|
1.7 kB | Preview Download |
md5:17bdb40501fb13a73fbaba8c182c742b
|
1.5 kB | Preview Download |
md5:f094a8d055efe1ba673e640567a38127
|
380 Bytes | Preview Download |
md5:739052fcb3e07c691c6e2e345e848a24
|
1.7 kB | Preview Download |
md5:ca0cb4bce6110863c4580d9a31b02b21
|
1.7 kB | Preview Download |
md5:db0f0a204e8723095774363b0f76560d
|
1.6 kB | Preview Download |
md5:4b164016a3adb5b6b6fbb659301bc527
|
2.5 kB | Preview Download |
md5:ecc7fb8aab6f7d253dc469d937b76414
|
3.2 MB | Preview Download |
md5:97252853d8d765fce068cc6a1df46329
|
4.0 kB | Preview Download |
md5:c0af8aa91870b6182a0607cb6028748c
|
2.6 kB | Preview Download |
md5:f395d8fdcd9e8436b6a0eb50bc2ed5ef
|
1.3 kB | Preview Download |
md5:ab802968336829dc303bdcfaad1ac3c1
|
3.5 kB | Preview Download |
md5:d10872d5ea1d6aaecc2a881f6753074a
|
2.1 kB | Preview Download |
md5:7b09460fb9cef4d07f4b52e4796a9e24
|
3.6 kB | Preview Download |
Additional details
- Eprint ID
- 70203
- Resolver ID
- CaltechAUTHORS:20160908-084105421
- DE-FG02-94ER40844
- Department of Energy (DOE)
- DE-FG02-87ER40315
- Department of Energy (DOE)
- DE-AC05-060R23177
- Department of Energy (DOE)
- Created
-
2016-09-09Created from EPrint's datestamp field
- Updated
-
2021-11-11Created from EPrint's last_modified field