1. Measurement of the Target-Normal Single-Spin Asymmetry in Quasi-Elastic Scattering from the Reaction $^3$He$^\uparrow(e,e^\prime)$
- Author
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Zhang, Y. -W., Long, E., Mihovilovič, M., Jin, G., Allada, K., Anderson, B., Annand, J. R. M., Averett, T., Boeglin, W., Bradshaw, P., Camsonne, A., Canan, M., Cates, G. D., Chen, C., Chen, J. P., Chudakov, E., De Leo, R., Deng, X., Deur, A., Dutta, C., Fassi, L. El, Flay, D., Frullani, S., Garibaldi, F., Gao, H., Gilad, S., Gilman, R., Glamazdin, O., Golge, S., Gomez, J., Hansen, O., Higinbotham, D. W., Holmstrom, T., Huang, J., Ibrahim, H., de Jager, C. W., Jensen, E., Jiang, X., John, J. St., Jones, M., Kang, H., Katich, J., Khanal, H. P., King, P., Korsch, W., LeRose, J., Lindgren, R., Lu, H. -J., Luo, W., Markowitz, P., Meziane, M., Michaels, R., Moffit, B., Monaghan, P., Muangma, N., Nanda, S., Norum, B. E., Pan, K., Parno, D., Piasetzky, E., Posik, M., Punjabi, V., Puckett, A. J. R., Qian, X., Qiang, Y., Qiu, X., Riordan, S., Ron, G., Saha, A., Sawatzky, B., Schiavilla, R., Schoenrock, B., Shabestari, M., Shahinyan, A., Širca, S., Subedi, R., Sulkosky, V., Tobias, W. A., Tireman, W., Urciuoli, G. M., Wang, D., Wang, K., Wang, Y., Watson, J., Wojtsekhowski, B., Ye, Y., Ye, Z., Zhan, X., Zhang, Y., Zheng, X., Zhao, B., and Zhu, L.
- Subjects
FOS: Physical sciences ,High Energy Physics::Experiment ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment - Abstract
We report the first measurement of the target single-spin asymmetry, $A_y$, in quasi-elastic scattering from the inclusive reaction $^3$He$^{\uparrow}(e,e^\prime)$ on a $^3$He gas target polarized normal to the lepton scattering plane. Assuming time-reversal invariance, this asymmetry is strictly zero for one-photon exchange. A non-zero $A_y$ can arise from the interference between the one- and two-photon exchange processes which is sensitive to the details of the sub-structure of the nucleon. An experiment recently completed at Jefferson Lab yielded asymmetries with high statistical precision at $Q^{2}=$ 0.13, 0.46 and 0.97 GeV$^{2}$. These measurements demonstrate, for the first time, that the $^3$He asymmetry is clearly non-zero and negative with a statistical significance of (8-10)$\sigma$. Using measured proton-to-$^{3}$He cross-section ratios and the effective polarization approximation, neutron asymmetries of $-$(1-3)% were obtained. The neutron asymmetry at high $Q^2$ is related to moments of the Generalized Parton Distributions (GPDs). Our measured neutron asymmetry at $Q^2=0.97$ GeV$^2$ agrees well with a prediction based on two-photon exchange using a GPD model and thus provides a new, independent constraint on these distributions.
- Published
- 2015
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