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

The JLab Qweak Collaboration is designing and constructing an experiment to measure the proton's weak charge, QpW, by measuring the parity violating asymmetry in elastic electron-proton scattering at very low momentum transfer. The standard model predicts QpW = 1 - 4 sin2 θw from the running of the weak mixing angle sin2 θw , corresponding to a 10σ effect in the experiment. The experiment will determine QpW with 4 % combined statistical and systematic uncertainties, which leads to 0.3 % uncertainty in sin2 θw . Installation of the experiment will begin in September 2009. Presented at the 20th Few-Body Conference, Pisa, Italy, 10-14 September 2007. (author)