arXiv · 1906.04075
Measurement of the single-spin asymmetry $A_y^0$ in quasi-elastic $^3$He$^\uparrow$($e,e'n$) scattering at $0.4 < Q^2 < 1.0$ GeV$/c^2$
Abstract
Due to the lack of free neutron targets, studies of the structure of the neutron are typically made by scattering electrons from either $^2$H or $^3$He targets. In order to extract useful neutron information from a $^3$He target, one must understand how the neutron in a $^3$He system differs from a free neutron by taking into account nuclear effects such as final state interactions and meson exchange currents. The target single spin asymmetry $A_y^0$ is an ideal probe of such effects, as any deviation from zero indicates effects beyond plane wave impulse approximation. New measurements of the target single spin asymmetry $A_y^0$ at $Q^2$ of 0.46 and 0.96 (GeV/$c)^2$ were made at Jefferson Lab using the quasi-elastic $^3\mathrm{He}^{\uparrow}(e,e'n)$ reaction. Our measured asymmetry decreases rapidly, from $>20\%$ at $Q^2=0.46$ (GeV/$c)^2$ to nearly zero at $Q^2=0.96$ (GeV$/c)^2$, demonstrating the fall-off of the reaction mechanism effects as $Q^2$ increases. We also observed a small $\epsilon$-dependent increase in $A_y^0$ compared to previous measurements, particularly at moderate $Q^2$. This indicates that upcoming high $Q^2$ measurements from the Jefferson Lab 12 GeV program can cleanly probe neutron structure from polarized $^3$He using plane wave impulse approximation.
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E. Long, Y. W. Zhang, M. Mihoviloviv, G. Jin, V. Sulkosky, A. Kelleher, B. Anderson, D. W. Higinbotham, S. Sirca, K. Allada, J. R. M. Annand, T. Averett, W. Bertozzi, W. Boeglin, P. Bradshaw, A. Camsonne, M. Canan, G. D. Cates, C. Chen, J. -P. Chen, E. Chudakov, R. De Leo, X. Deng, A. Deur, C. Dutta, L. El Fassi, D. Flay, S. Frullani, F. Garibaldi, H. Gao, S. Gilad, R. Gilman, O. Glamazdin, S. Golge, J. Gomez, J. -O. Hansen, T. Holmstrom, J. Huang, H. Ibrahim, C. W. de Jager, E. Jensen, X. Jiang, M. Jones, H. Kang, J. Katich, H. P. Khanal, P. M. King, W. Korsch, J. LeRose, R. Lindgren, H. -J. Lu, W. Luo, P. Markowitz, M. Meziane, R. Michaels, B. Moffit, P. Monaghan, N. Muangma, S. Nanda, B. E. Norum, K. Pan, D. Parno, E. Piasetzky, M. Posik, V. Punjabi, A. J. R. Puckett, X. Qian, Y. Qiang, X. Qui, S. Riordan, A. Saha, B. Sawatzky, M. Shabestari, A. Shahinyan, B. Shoenrock, J. St. John, R. Subedi, W. A. Tobias, W. Tireman, G. M. Urciuoli, D. Wang, K. Wang, Y. Wang, J. Watson, B. Wojtsekhowski, Z. Ye, X. Zhan, Y. Zhang, X. Zheng, B. Zhao, L. Zhu. 2019-06-10. Measurement of the single-spin asymmetry $A_y^0$ in quasi-elastic $^3$He$^\uparrow$($e,e'n$) scattering at $0.4 < Q^2 < 1.0$ GeV$/c^2$. https://doi.org/10.1016/j.physletb.2019.134875
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