We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely polarized 3 GeV electrons from unpolarized protons at Q2=0.15, 0.25 (GeV/c)2. The results are inconsistent with calculations solely using the elastic nucleon intermediate state and generally agree with calculations with significant inelastic hadronic intermediate state contributions. An provides a direct probe of the imaginary component of the 2γ exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.
Physical Review Letters
Armstrong, D. S.; Biselli, Angela; and G0 Collaboration, "Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering" (2007). Physics Faculty Publications. 23.
D. S. Armstrong et al. [G0 Collaboration], "Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering", Physics Review Letters, Volume 99, Issue 99 092301 (2007). DOI: 10.1103/PhysRevLett.99.092301