A new precision measurement of parity violation in electron scattering from the proton at very low Q 2 and forward angles is being prepared for execution at Jefferson Laboratory (JLab). The experiment is a direct challenge to the predictions of the Standard Model of quarks and leptons and is a search for new physics. There exists a unique opportunity to carry out the first precision measurement of the weak charge of the proton,
, by building on technical advances that have been made at Jefferson Laboratory's world-leading parity violating electron scattering program and by using the results of earlier experiments to constrain hadronic corrections. A 2200 hour measurement of the parity violating asymmetry in elastic electron-proton scattering at Q 2 = 0.03 (GeV/c) 2 employing 180 μA of 85% polarized beam on a 0.35 m long liquid hydrogen target will determine the proton's weak charge with 4% combined statistical and systematic errors. The Standard Model makes a firm prediction of Q p W , based on the 'running' of the weak mixing angle sin 2 (θ W ) from the Z 0 pole down to lower energies, corresponding to a 9 σ effect at the envisaged experiment. Any significant deviation of sin 2 (θ W ) from the Standard Model prediction at low Q 2 would be a signal of new physics, where as agreement would place new and strict constraints on possible Standard Model extensions. In the absence of new physics the envisaged experiment will provide a 0.3% determination of sin 2 (θ W ), making this a very competitive standalone measurement of the weak mixing angle indeed.