Precision Measurement of the Beam-Normal Single-Spin Asymmetry in Forward-Angle Elastic Electron-Proton Scattering

A beam-normal single-spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable related to the imaginary part of the two-photon exchange process. We report a 2% precision measurement of the beam-normal single-spin asymmetry in elastic el...

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Published in:arXiv.org 2020-08
Main Authors: collaboration, QWeak, Androic, D, Armstrong, D S, Asaturyan, A, Bartlett, K, Beaufait, J, Beminiwattha, R S, Benesch, J, Benmokhtar, F, Birchall, J, Carlini, R D, Cornejo, J C, S Covrig Dusa, Dalton, M M, Davis, C A, Deconinck, W, Dowd, J F, Dunne, J A, Dutta, D, Duvall, W S, Elaasar, M, Falk, W R, Finn, J M, est, T, Gal, C, Gaskell, D, Gericke, M T W, Grames, J, Gray, V M, Grimm, K, Guo, F, Hoskins, J R, Jones, D, Jones, M K, Jones, R T, Kargiantoulakis, M, King, P M, Korkmaz, E, Kowalski, S, Leacock, J, Leckey, J P, Lee, A R, Lee, J H, Lee, L, MacEwan, S, Mack, D, Magee, J A, Mahurin, R, Mammei, J, Martin, J W, McHugh, M J, Meekins, D, Mei, J, Mesick, K E, Michaels, R, Micherdzinska, A, Mkrtchyan, A, Mkrtchyan, H, Morgan, N, Narayan, A, Ndukum, L Z, Nelyubin, V, Nuruzzaman, W T H van Oers, Owen, V F, Page, S A, Pan, J, Paschke, K D, Phillips, S K, Pitt, M L, Radloff, R W, Rajotte, J F, Ramsay, W D, Roche, J, Sawatzky, B, Seva, T, Shabestari, M H, Silwal, R, Simicevic, N, Smith, G R, Solvignon, P, Spayde, D T, Subedi, A, Subedi, R, Suleiman, R, Tadevosyan, V, Tobias, W A, Tvaskis, V, Waidyawansa, B, Wang, P, Wells, S P, Wood, S A, Yang, S, Zang, P, Zhamkochyan, S
Format: Article
Language:English
Subjects:
Asymmetry
Elastic scattering
Electron spin
Exchanging
Forward scattering
Photons
Proton beams
Proton scattering
Scattering angle
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Summary:A beam-normal single-spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable related to the imaginary part of the two-photon exchange process. We report a 2% precision measurement of the beam-normal single-spin asymmetry in elastic electron-proton scattering with a mean scattering angle of theta_lab = 7.9 degrees and a mean energy of 1.149 GeV. The asymmetry result is B_n = -5.194 +- 0.067 (stat) +- 0.082 (syst) ppm. This is the most precise measurement of this quantity available to date and therefore provides a stringent test of two-photon exchange models at far-forward scattering angles (theta_lab -> 0) where they should be most reliable.
ISSN:2331-8422
DOI:10.48550/arxiv.2006.12435