Proton GE/GM from beam-target asymmetry
Abstract
The ratio of the proton's electric to magnetic form factor, GE/GM, can be extracted in elastic electron-proton scattering by measuring either cross sections, beam-target asymmetry or recoil polarization. Separate determinations of GE/GM by cross sections and recoil polarization observables disagree for Q2 > 1 (GeV/c)2. Measurement by a third technique might uncover an unknown systematic error in either of the previous measurements. The beam-target asymmetry has been measured for elastic electron-proton scattering at Q2 = 1.51 (GeV/c)2 for target spin orientation aligned perpendicular to the beam momentum direction. This is the largest Q2 at which GE/GM has been determined by a beam-target asymmetry experiment. The result, μGE/GM = 0.884 +/- 0.027 +/- 0.029, is compared to previous world data.
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