ABSTRACT:
The Qweak Experiment at Jefferson Lab finished two years of data taking
in May 2012.  Using a 1.16 GeV, 89% longitudinally polarized electron
beam, the experiment measured the parity-violating asymmetry in elastic
electron-proton scattering at low Q^2 to access the weak charge of the
proton.  The Standard Model firmly predicts the proton's weak charge
from the running of the weak mixing angle, to which the weak charge can
be directly related to.  Through a precise measurement of the
sub-part-per-million asymmetry, Qweak will make the first determination
of the proton's weak charge to a precision of 4%, and thus the weak
mixing angle at low Q^2 to 0.3%. This low-energy precision measurement
will test the predictions of the Standard Model and be sensitive to new
physics at the TeV scale, complementing direct searches at the LHC.  The
experimental method and results from the commissioning run, comprising
4% of the total data acquired, will be presented.