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arXiv · 1404.4003

A Precision Measurement of the Neutron Twist-3 Matrix Element $d_2^n$: Probing Color Forces

M. Posik·D. Flay·D. S. Parno·K. Allada·W. Armstrong·T. Averett·F. Benmokhtar·W. Bertozzi·A. Camsonne·M. Canan·G. D. Cates·C. Chen·J. -P. Chen·S. Choi·E. Chudakov·F. Cusanno·M. M. Dalton·W. Deconinck·C. W. de Jager·X. Deng·A. Deur·C. Dutta·L. El Fassi·G. B. Franklin·M. Friend·H. Gao·F. Garibaldi·S. Gilad·R. Gilman·O. Glamazdin·S. Golge·J. Gomez·L. Guo·O. Hansen·D. W. Higinbotham·T. Holmstrom·J. Huang·C. Hyde·H. F. Ibrahim·X. Jiang·G. Jin·J. Katich·A. Kelleher·A. Kolarkar·W. Korsch·G. Kumbartzki·J. J. LeRose·R. Lindgren·N. Liyanage·E. Long·A. Lukhanin·V. Mamyan·D. McNulty·Z. -E. Meziani·R. Michaels·M. Mihovilovič·B. Moffit·N. Muangma·S. Nanda·A. Narayan·V. Nelyubin·B. Norum·Nuruzzaman·Y. Oh·J. C. Peng·X. Qian·Y. Qiang·A. Rakhman·S. Riordan·A. Saha·B. Sawatzky·M. H. Shabestari·A. Shahinyan·S. Širca·P. Solvignon·R. Subedi·V. Sulkosky·W. A. Tobias·W. Troth·D. Wang·Y. Wang·B. Wojtsekhowski·X. Yan·H. Yao·Y. Ye·Z. Ye·L. Yuan·X. Zhan·Y. Zhang·Y. -W. Zhang·B. Zhao·X. Zheng
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Abstract

Double-spin asymmetries and absolute cross sections were measured at large Bjorken $x$ (0.25 $ \le x \le $ 0.90), in both the deep-inelastic and resonance regions, by scattering longitudinally polarized electrons at beam energies of 4.7 and 5.9 GeV from a transversely and longitudinally polarized $^3$He target. In this dedicated experiment, the spin structure function $g_2$ on $^3$He was determined with precision at large $x$, and the neutron twist-three matrix element $d_2^n$ was measured at $\left< Q^2\right>$ of 3.21 and 4.32 GeV$^2$/$c^2$, with an absolute precision of about $10^{-5}$. Our results are found to be in agreement with lattice QCD calculations and resolve the disagreement found with previous data at $\left< Q^2\right> =$ 5 GeV$^2$/$c^2$. Combining $d_2^n$ and a newly extracted twist-four matrix element, $f_2^n$, the average neutron color electric and magnetic forces were extracted and found to be of opposite sign and about 30 MeV/fm in magnitude.

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M. Posik, D. Flay, D. S. Parno, K. Allada, W. Armstrong, T. Averett, F. Benmokhtar, W. Bertozzi, A. Camsonne, M. Canan, G. D. Cates, C. Chen, J. -P. Chen, S. Choi, E. Chudakov, F. Cusanno, M. M. Dalton, W. Deconinck, C. W. de Jager, X. Deng, A. Deur, C. Dutta, L. El Fassi, G. B. Franklin, M. Friend, H. Gao, F. Garibaldi, S. Gilad, R. Gilman, O. Glamazdin, S. Golge, J. Gomez, L. Guo, O. Hansen, D. W. Higinbotham, T. Holmstrom, J. Huang, C. Hyde, H. F. Ibrahim, X. Jiang, G. Jin, J. Katich, A. Kelleher, A. Kolarkar, W. Korsch, G. Kumbartzki, J. J. LeRose, R. Lindgren, N. Liyanage, E. Long, A. Lukhanin, V. Mamyan, D. McNulty, Z. -E. Meziani, R. Michaels, M. Mihovilovič, B. Moffit, N. Muangma, S. Nanda, A. Narayan, V. Nelyubin, B. Norum, Nuruzzaman, Y. Oh, J. C. Peng, X. Qian, Y. Qiang, A. Rakhman, S. Riordan, A. Saha, B. Sawatzky, M. H. Shabestari, A. Shahinyan, S. Širca, P. Solvignon, R. Subedi, V. Sulkosky, W. A. Tobias, W. Troth, D. Wang, Y. Wang, B. Wojtsekhowski, X. Yan, H. Yao, Y. Ye, Z. Ye, L. Yuan, X. Zhan, Y. Zhang, Y. -W. Zhang, B. Zhao, X. Zheng. 2014-07-03. A Precision Measurement of the Neutron Twist-3 Matrix Element $d_2^n$: Probing Color Forces. https://doi.org/10.1103/physrevlett.113.022002

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