This MRI project will build a large, novel magneto-electrostatic spectrometer, highly optimized for precision measurements of four key parameters describing neutron beta decay: "a", the electron-neutrino correlation, "b", the Fierz interference term, as well as "A/B/C", the beta/neutrino/proton asymmetries. The device will be mounted at the Fundamental Neutron Physics Beamline (FnPB) of the Spallation Neutron Source (SNS), Oak Ridge National Laboratory (ORNL). The proposed spectrometer will be a premier instrument for precision study (at the level of a part in ~1000) of neutron beta decay in the US and in the world. The experiment is expected to provide critical results toward resolving longstanding discrepancies in the neutron decay world data set. The proposed device, coupled with state of the art neutron beam, will enable the collaboration to set stringent limits on certain processes that would extend the Standard Model, with strong implications in astrophysics. The spectrometer will be developed and built by a consortium comprising University of Virginia (UVa), Arizona State University (ASU), and ORNL, with UVa as the lead institution.
Besides advancing fundamental science, the proposed project's impact is mainly in higher education. The UVa and the ASU groups have established records of training Ph.D. and postdoctoral scientists who have proceeded to assume productive roles in academia, research, and industry. Several undergraduate students will gain valuable research experience working on the proposed project; four have already been deeply involved in the design phase. As well, the PIs' groups have an established record of including members of underrepresented minorities (in recent past there have been two African American Ph.D. students, as well as women Ph.D. students, postdocs, and undergraduate students). The PIs are strongly committed to attracting members of underrepresented groups, to help broaden the human resource base of the field.