Strange Form Factors and a Low Energy Standard Model Test

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This grant supports research that seeks the answer to two fundamental questions about matter. The first is what role does the sea of strange quark-antiquark pairs in the nucleon play in the determination of its electromagnetic properties? We are participating in the G0 experiment at Thomas Jefferson National Accelerator Facility to address this issue. The experiment measures the parity-violating asymmetry in the scattering of polarized electrons from the proton and deuteron over a wide range of momentum transfers; this will allow for the strange electric and magnetic form factors to be separately extracted. This experiment will be in a data-taking and analysis phase during this grant period. The second question is whether or not there is any new physics beyond the Standard Model of electroweak physics. This question will be addressed by the Qweak experiment at TJNAF, which will measure the proton's neutral weak charge via parity-violating electon scattering at very low momentum transfer. The proton's weak charge has a well-defined prediction in the Standard Model; a precise measurement of it is sensitive to many poplular scenarios for extending the Standard Model. This experiment will be in a construction and early data-taking phase during the period of this grant. Our group will design and construct three pieces of hardware for the Qweak experiment - a set of drift chambers, a luminosity monitor, and a mini-torus magnet. These projects involve many hardware and software tasks that will contribute to the education of a postdoctoral fellow and graduate and undergraduate students working on the project.