Precision Measurement of the Beam-Normal Single-Spin Asymmetry in Forward-Angle Elastic Electron-Proton Scattering
Abstract
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.
Keywords
Cite
@article{arxiv.2006.12435,
title = {Precision Measurement of the Beam-Normal Single-Spin Asymmetry in Forward-Angle Elastic Electron-Proton Scattering},
author = {QWeak collaboration and D. Androic and D. S. Armstrong and A. Asaturyan and K. Bartlett and J. Beaufait and R. S. Beminiwattha and J. Benesch and F. Benmokhtar and J. Birchall and R. D. Carlini and J. C. Cornejo and S. Covrig Dusa and M. M. Dalton and C. A. Davis and W. Deconinck and J. F. Dowd and J. A. Dunne and D. Dutta and W. S. Duvall and M. Elaasar and W. R. Falk and J. M. Finn and T. Forest and C. Gal and D. Gaskell and M. T. W. Gericke and J. Grames and V. M. Gray and K. Grimm and F. Guo and J. R. Hoskins and D. Jones and M. K. Jones and R. T. Jones and M. Kargiantoulakis and P. M. King and E. Korkmaz and S. Kowalski and J. Leacock and J. P. Leckey and A. R. Lee and J. H. Lee and L. Lee and S. MacEwan and D. Mack and J. A. Magee and R. Mahurin and J. Mammei and J. W. Martin and M. J. McHugh and D. Meekins and J. Mei and K. E. Mesick and R. Michaels and A. Micherdzinska and A. Mkrtchyan and H. Mkrtchyan and N. Morgan and A. Narayan and L. Z. Ndukum and V. Nelyubin and Nuruzzaman and W. T. H van Oers and V. F. Owen and S. A. Page and J. Pan and K. D. Paschke and S. K. Phillips and M. L. Pitt and R. W. Radloff and J. F. Rajotte and W. D. Ramsay and J. Roche and B. Sawatzky and T. Seva and M. H. Shabestari and R. Silwal and N. Simicevic and G. R. Smith and P. Solvignon and D. T. Spayde and A. Subedi and R. Subedi and R. Suleiman and V. Tadevosyan and W. A. Tobias and V. Tvaskis and B. Waidyawansa and P. Wang and S. P. Wells and S. A. Wood and S. Yang and P. Zang and S. Zhamkochyan},
journal= {arXiv preprint arXiv:2006.12435},
year = {2020}
}
Comments
6 pages, 3 figures; Slightly revised version, after referee's comments; accepted in PRL