Vector analyzing power in elastic electron-nucleus scattering

Vector analyzing power Aₙ is calculated for elastic electron scattering from a variety of spin-zero nuclei at energies from 14 MeV to 3 GeV. Time-reversal symmetry ensures that Aₙ vanish in the first Born approximation. Therefore Aₙ depends on Coulomb distortions and can be large for scattering from heavy nuclei. The vector analyzing power is a potential source of systematic error for parity-violation experiments. We find that Aₙ=-0.361 ppm for the kinematics of the parity radius experiment involving 850-MeV electrons scattering at 6^^∘ from ²⁰⁸Pb. This is comparable with the parity-violating asymmetry. However, for HAPPEX He involving 3-GeV electrons scattering on ⁴He we find that Aₙ is very small.