Final Results from the Jefferson Lab Qweak Experiment and Constraints on Physics Beyond the Standard Model
2019 August 19
2019 August 23
The Qweak ep elastic scattering experiment used to extract an asymmetry at Q^2 = 0.0248 GeV^2 will be described. The final result was −226.5 ± 9.3 ppb- the most precise ep asymmetry ever measured. Some of the backgrounds and corrections applied in the experiment will be explained and quantified, and some of the experimental challenges will be described. Several methods used to extract consistent values of the proton’s weak charge Q_w(p) from our asymmetry measurement will be outlined. We also show the multi-TeV mass reach for beyond-the-Standard-Model physics obtained from our determination of the proton’s weak charge, and discuss our sensitivity to specific examples of new physics like compositeness. From the proton’s weak charge, a result for the fundamental standard model parameter sin^2θ_W is obtained at the energy scale of our experiment. We compare that to the few other determinations of sin^2θ_W available in the literature, as well as the predicted behaviour based on SM input.