Weak Polarized Electron Scattering

Scattering polarized electrons provides an important probe of the weak interactions. Precisely measuring the parity-violating left–right cross-section asymmetry (ALR) is the goal of a number of experiments that have recently been completed or are in progress. The experiments are challenging, given that ALR is small, typically between 10⁻⁴ and 10⁻⁸. By carefully choosing appropriate targets and kinematics, one can isolate various pieces of the weak Lagrangian, providing a search for physics beyond the Standard Model. For other choices, unique features of the strong interaction are being studied, including the radius of the neutron density in heavy nuclei, charge symmetry violation, and higher-twist terms. This article reviews the theory behind the experiments, as well as the general techniques used in the experimental program.