The Qweak Experiment : Design of Quartz \v{C}erenkov Detectors for a Measurement of the Proton Weak Charge

The Qweak experiment at Jefferson Lab aims to make a 4\% measurement of the parity-violating asymmetry in elastic scattering at very low $Q^2$ of a longitudinally polarized electron beam on a proton target. The experiment will measure the weak charge of the proton, and thus the weak mixing angle at low energy scale, providing a precision test of the Standard Model. The experiment is currently being constructed and is scheduled for a 2200 hour measurement starting in 2009, employing: an 80\% polarized, 180 $\mu$ A, 1.2 GeV electron beam; a 35 cm liquid hydrogen target; and a toroidal magnet to focus electrons scattered at 9$^{\circ}$ forward angle, corresponding to $Q^2 = 0.03~{\rm (GeV/c)^2}$. The experiment will run at an event rate of over 6 GHz. This requires current mode detection of the scattered electrons, using synthetic quartz \v{C}erenkov detectors. In this talk we will present a brief introduction to the experiment, with a focus on the design and status of the main \v{C}erenkov detectors.