LEAPS-MPS: Precision Measurements of Neutron Beta Decay to Test Fundamental Symmetries

Eastern Kentucky University, Richmond KY

Investigators

Abstract

This award supports Dr. Fry at Eastern Kentucky University in a project that will impact science and society through research activities aimed at precisely determining the neutron lifetime and two of its decay parameters (known as “a” and “b”), as well as training and mentoring undergraduate students in technical areas that will prepare them for careers in STEM fields. Precisely determining the neutron’s decay parameters can provide sensitive tests of the Standard Model and achieving that has been identified as a high priority in the current Long-Range Plan for Nuclear Science by the Nuclear Science Advisory Committee. Exciting preliminary results have already generated public interest and will continue to do so with further results from this work. The scales of the neutron “a” and “b” (Nab) experiment and the Beam Lifetime 3 (BL3) and its use of techniques from many subfields of physics lends itself to hands-on student participation and the development of a broad understanding of physical principles and experimental techniques. The project will help train motivated students at EKU, provide research opportunities in larger scale collaborations, and conduct team-based science. The award will employ students at a living wage at EKU, which will help retain students and increase future student success by keeping them engaged in activities in their major, therefore further adding to the scientific workforce. One of the cornerstones of the Standard Model of physics is the unitarity of the quark mixingmatrix (CKM matrix). This symmetry can be tested by combining precise measurements of the ratio of the axial-vector and vector coupling constants, and the neutron lifetime. Currently, measurements of the neutron lifetime using different methods are in conflict with each other and resolving this discrepancy is of high intellectual priority. Additionally, the neutron lifetime has cosmological implications as it was a key factor in the formation of the light elements during Big Bang Nucleosynthesis (BBN). The uncertainty in the neutron lifetime is the largest contribution to the uncertainty in the primordial helium abundance, YP. In these cosmological models, YP is related to important parameters such as the expansion of the universe and the number of effective neutrino species; resolving the neutron lifetime puzzle is top priority in nuclear science with implications in the interplay of cosmology and particle physics. The award will involve students in hands-on experiences in the lab at Eastern Kentucky University and at Oak Ridge National Lab. Student-centered projects will include addressing an important systematic effect in the Nab experiment by conducting an in-situ timing study to characterize silicon detectors to less than or equal to 1 ns, developing complex Monte Carlo simulations for systematic studies in the Nab and BL3 experiments, and to develop a data analysis server for the BL3 experiment. This work will give students an extraordinary experience at a regional university, travel to a national lab and experience with a larger collaboration and help them carve out meaningful roles in the scientific workforce. This project is jointly funded by the Division of Physics within the Mathematical and Physical Sciences Directorate and the Established Program to Stimulate Competitive Research (EPSCoR). 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.