The Measurement of a Lepton-Lepton Electroweak Reaction (MOLLER) experiment proposes to measure the parity-violating asymmetry in electron-electron (Møller) scattering. The measurement will be carried out at Jefferson Laboratory's state-of-the-art accelerator by rapidly flipping the longitudinal polarization of electrons that have been accelerated to 11 GeV and observing the resulting fractional difference in the probability of these electrons scattering off atomic electrons in a liquid hydrogen target. This asymmetry is proportional to the weak charge of the electron, which in turn is a function of the electroweak mixing angle, a fundamental parameter of the electroweak theory. The accuracy of the proposed measurement allows for a low energy determination of the mixing angle with precision on par with the two best measurements at electron-positron colliders.
The MOLLER experiment has 11 major subsystems, including the target, spectrometer and collimators, the main detectors and several types of auxilliary detectors.