Parity violating elastic electron scattering and Coulomb distortions

Parity violating elastic electron-nucleus scattering provides an accurate and model-independent measurement of neutron densities, because the Z⁰ couples primarily to neutrons. Coulomb distortion corrections to the parity violating asymmetry A_l are calculated exactly using a relativistic optical model. Distortions significantly reduce A_l in a heavy nucleus. However, even with distortions, an experiment to measure the neutron radius is feasible. This will aid the interpretation of future atomic parity violation measurements and provide fundamental nuclear structure information. Coulomb distortions and small differences between neutron and proton radii could be important for a standard model test on ⁴He, ¹²C, or ¹⁶O.