Parity-Violating Electron Scattering: Hadron Structure and New Physics

Parity-violating electron scattering opens up a new window on the structure of matter. Usually, electron scattering is thought of as an electromagnetic process, which certainly would not violate parity! But by measuring tiny parity-violating signals, the weak neutral-current interaction between the electron and the target can be isolated and measured precisely. This has led to a series of experiments that have sought to characterize the strange quark structure of the proton. The difference in the way the photon and the Z-boson couple to quarks gives these experiments their sensitivity. More recent experiments have become sufficiently precise to extract the weak mixing angle itself, the parameter that describes gamma-Z mixing in the standard model. In this way, by comparing with measurements done at high-energy collider experiments, the running of the weak mixing angle with energy scale can be deduced and compared with standard-model predictions. If a deviation from the standard model were found, this could herald the effects of new physics at the TeV scale. I review these and other applications in the field of parity-violating electron scattering, focusing on recent progress, and with a view the future of this exciting and important field.