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Published July 5, 2011 | Published
Journal Article Open

Transverse Beam Spin Asymmetries at Backward Angles in Elastic Electron-Proton and Quasielastic Electron-Deuteron Scattering


We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasielastic scattering on the deuteron, at backward angles (lab scattering angle of 108°) for Q^2=0.22  GeV^2/c^2 and 0.63  GeV^2/c^2 at beam energies of 362 and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single-photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (πN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasistatic deuterium approximation, and is also in agreement with theory.

Additional Information

© 2011 American Physical Society. Received 24 March 2011; published 5 July 2011. We gratefully acknowledge the strong technical contributions to this experiment from many groups: Caltech, Illinois, LPSC-Grenoble, IPN-Orsay, TRIUMF, and particularly the Accelerator and Hall C groups at Jefferson Lab. CNRS (France), DOE (U.S.), NSERC (Canada), and NSF (U.S.) supported this work in part.

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Published - Androic2011p15149Phys_Rev_Lett.pdf


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