Measuring the weak charge of the proton at Jefferson Lab: A search for physics beyond the standard model

The JLab Q (weak) Collaboration is designing and constructing an experiment to measure the proton's weak charge, Q (W) (p) , by measuring the parity violating asymmetry in elastic electron-proton scattering at very low momentum transfer. The standard model predicts Q (W) (p) = 1 - 4 sin(2) theta (w) from the running of the weak mixing angle sin(2) theta (w) , corresponding to a 10 sigma effect in the experiment. The experiment will determine Q (W) (p) with 4% combined statistical and systematic uncertainties, which leads to 0.3% uncertainty in sin(2) theta (w) . Installation of the experiment will begin in September 2009.