Study of Two-Photon Exchange via the Beam Transverse Single Spin Asymmetry in Electron-Proton Elastic Scattering at Forward Angles over a Wide Energy Range
Name
PhysRevLett.124.122003.pdf
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349.64 KB
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Author(s)
Deconinck, Wouter
Kowalski, Stanley B
Date Issued
March 27, 2020
Journal
Physical review letters
Publisher
American Physical Society
Citation
Guo, B. et al. “Study of Two-Photon Exchange via the Beam Transverse Single Spin Asymmetry in Electron-Proton Elastic Scattering at Forward Angles over a Wide Energy Range”, Physical review letters, vol. 124, 2020, 122003 © 2020 The Author(s)
Version
Final published version
Abstract
We report on a new measurement of the beam transverse single spin asymmetry in electron-proton elastic scattering, A_{⊥}^{ep}, at five beam energies from 315.1 to 1508.4 MeV and at a scattering angle of 30°<θ<40°. The covered Q^{2} values are 0.032, 0.057, 0.082, 0.218, 0.613 (GeV/c)^{2}. The measurement clearly indicates significant inelastic contributions to the two-photon-exchange (TPE) amplitude in the low-Q^{2} kinematic region. No theoretical calculation is able to reproduce our result. Comparison with a calculation based on unitarity, which only takes into account elastic and πN inelastic intermediate states, suggests that there are other inelastic intermediate states such as ππN, KΛ, and ηN. Covering a wide energy range, our new high-precision data provide a benchmark to study those intermediate states.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1103/PhysRevLett.124.122003
