Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering
We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 values of 0.15 and 0.25 (GeV/c)^2 with results of A_n = -4.06 +- 0.99(stat) +- 0.63(syst) and A_n = -4.82 +- 1.87(stat) +- 0.98(syst) ppm. These results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the two-photon exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE - Office of Energy Research (ER)
- DOE Contract Number:
- AC05-06OR23177
- OSTI ID:
- 913574
- Report Number(s):
- JLAB-PHY-07-651; DOE/OR/23177-0130; arXiv:0705.1525; PRLTAO; TRN: US0800777
- Journal Information:
- Phys. Rev. Lett., Vol. 99, Issue 09; ISSN 0031-9007
- Country of Publication:
- United States
- Language:
- English
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