Probing the Standard Model with Parity-Violating Electron Scattering

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This grant supports research that seeks to answer a fundamental question about matter. What is the nature of any new physics not described by the Standard Model of electroweak physics? This question will be addressed by the Qweak experiment at the Thomas Jefferson National Accelerator Facility (TJNAF). It will measure the proton's neutral weak charge via parity-violating electron 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 popular scenarios for extending the Standard Model. Our group has built and installed three hardware systems for the experiment - a set of horizontal drift chambers, a set of luminosity monitors, and halo and low beam current monitoring detectors. During the period of this grant, we will maintain our hardware systems during data taking, analyze data, and extract physics results. We will also begin work on a newly approved TJNAF experiment to test the Standard Model - the MOLLER experiment - a precision measurement of the parity-violating asymmetry in the elastic scattering of polarized electrons on unpolarized electrons. The projects we are working on involve a wide range of hardware and software tasks that will contribute to the education of graduate and undergraduate students working on the project.