A Precision Test of the Standard Model with Parity-Violating Electron Scattering

This award supports research that seeks to answer a fundamental question about matter. What is the nature of new physics not described by the Standard Model - our current framework of how particles and forces interact? This question will be addressed by a precise measurement of the weak charge of the electron in a large 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 program will support graduate and undergraduate students, who will form an essential part of this project.

The supported activities cover a range of hardware and software tasks that will provide excellent training for these individuals. 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 award will support activities on the MOLLER experiment, a parity-violating electron scattering experiment at Jefferson Lab. The MOLLER experiment is an approved experiment making use of the upgraded 12 GeV accelerator at the lab. It will measure the electron’s neutral weak charge by making a precise measurement of the parity-violating asymmetry in the elastic scattering of polarized electrons from unpolarized electrons at 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. The result would have excellent sensitivity to many beyond the Standard Model scenarios. During the period of this project, the research team will make important contributions to this experiment: construction and installation of the scattered beam monitor and scanner systems, coordination of the MOLLER beam charge monitor upgrades, installation of a halo monitor system, and data analysis code development.

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.