Probing the Standard Model with Parity-Violating Electron Scattering

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Our current understanding of how particles and forces interact is called ‘The Standard Model” of physics. But is there physics beyond the standard model? This question will be addressed by a precision measurement of the weak charge of the electron in a collaborative experiment at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News, Virginia. The electron’s weak charge is the weak force analog of the common electric charge of the electron, and it is precisely predicted in the Standard Model. Any deviation of the measurement from this prediction could be evidence of yet undiscovered massive particles that represent new physics beyond our current understanding. The anticipated activities cover a range of hardware and software tasks that will provide excellent training for the students working on the project. This training in fundamental research provides a strong basis for careers both in basic research and in more applied research and industry. The funds provided by this project will support activities on the MOLLER experiment. MOLLER is an approved experiment at Jefferson Lab that takes advantage of the recent 12 GeV energy upgrade for the accelerator. The experiment will measure the electron’s neutral weak charge by making a precision measurement of the parity-violating asymmetry in the elastic scattering of polarized electrons on unpolarized electrons at a very low momentum transfer. This will result in a determination of the weak mixing angle at low energy with a precision comparable to the best determinations from high energy colliders. It will have excellent sensitivity to physics scenarios that extend beyond the Standard Model. During the period of this project, our group will make important contributions to this experiment: including development and construction of the scattered beam monitor system, development and construction of the scanner system, coordination of the MOLLER beamline including beam charge monitor upgrades and beam modulation system, installation of a halo monitor system, and simulation design studies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.