Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)




David Armstrong


Qweak is an experiment currently running at the Thomas Jefferson National Accelerator Facility that uses parity-violating elastic electron-proton scattering to measure the weak charge of the proton QPweak . Longitudinally polarized electrons are scattered off a liquid hydrogen target and pass through a toroidal-field magnetic spectrometer. This experiment is a sensitive test for physics beyond the Standard Model, as QPweak is well predicted in the Standard Model. This dissertation describes the first direct measurement of QPweak . The precision that will be generated by the final 4% measurement will allow the probing of certain classes of new physics up to 2.5 TeV. In this dissertation, the design and status of the complete experiment are discussed, including the details of the asymmetry measurements and preliminary results from several studies of experimental systematics. This dissertation also includes a full description of the design, construction, commissioning, and use of the vertical drift chambers (VDC) used in the Qweak experiment to measure the scattered electron's profile and the momentum transfer (Q 2) of the ep scattering. The Q 2 was measured to be 0.0274 +/- 0.0013 GeV2/c 2 and QPweak was measured to be 0.102 +/- 0.036, which is consistent with the Standard Model.



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