New Measurements of the Transverse Beam Asymmetry for Elastic Electron Scattering from Selected Nuclei

Abstract

We have measured the beam-normal single-spin asymmetry ${A}_{n}$ in the elastic scattering of 1--3 GeV transversely polarized electrons from $^{1}\mathrm{H}$ and for the first time from $^{4}\mathrm{He}$, $^{12}\mathrm{C}$, and $^{208}\mathrm{Pb}$. For $^{1}\mathrm{H}$, $^{4}\mathrm{He}$, and $^{12}\mathrm{C}$, the measurements are in agreement with calculations that relate ${A}_{n}$ to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the $^{208}\mathrm{Pb}$ result is significantly smaller than the corresponding prediction using the same formalism. These results suggest that a systematic set of new ${A}_{n}$ measurements might emerge as a new and sensitive probe of the structure of heavy nuclei.