A Search for Physics beyond the Standard Model: Update on the Qweak Experiment

The Qweak experiment aims to make a precision measurement of the proton's weak charge ($Q^{P}_{weak})$ using parity-violating elastic electron-proton scattering. The goal, a $\pm $4{\%} measurement of the proton's weak charge ($Q^{P}_{weak}$ \textit{= 1 - 4sin}$^{2}$\textit{$\theta $}$_{W}$ ), will allow for a $\pm $0.3{\%} determination of \textit{sin}$^{2}$\textit{$\theta $}$_{W}$ at low momentum transfers ($Q^{2}$\textit{ $\sim $ 0.026 GeV}$^{2}/c^{2})$, and provide a measure of the running of \textit{sin}$^{2}$\textit{$\theta $}$_{W}$ . Furthermore, since $Q^{P}_{weak}$ is well-determined in the Standard Model, this experiment will be a sensitive test for physics beyond the Standard Model. The experiment, which scatters longitudinally polarized electrons off a 0.35m long liquid hydrogen target, is currently running in Hall C at the Thomas Jefferson National Accelerator Facility. At this time, only a fraction of the data required to reach the desired statistical uncertainties has been collected, with the bulk of the data-taking scheduled for late-2011 and 2012. The design and present status of the Qweak experiment will be summarized in this talk.