Precision Measurements and Fundamental Symmetries

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The research supported by this award will test precise Standard Model predictions and can provide solid signals of new physics by 1) measuring the magnetic signature of the muon, an exotic elementary particle that is produced in abundance at the Fermi National Accelerator Laboratory and 2) studying the detailed behavior of neutrons as they decay. This work addresses the deepest questions that we can ask: what is matter made of, how did it come to be, and how does it interact. At the same time this work addresses the technical demands of the two experiments by pushing the limits of magnetic field measurements. Many potential additional applications of these techniques may be extended into biology, neuroscience and medicine. This research provides challenging research projects for graduate and undergraduate students at the University of Michigan. A diverse cohort of graduate students are working on aspects of this research and will join former students in contributing to the National interest as teachers, researchers in physics and biomedical fields and leaders in industry.This research consists of advancing two precision measurements: the muon magnetic moment anomaly g - 2 and the beta-neutrino asymmetry parameter in neutron decay. These address the deepest question in elementary particle and nuclear physics, namely what lies beyond the Standard Model, by putting precise predictions to the test in systems most sensitive to new physics. This University of Michigan group is contributing to the Fermilab Muon g-2 experiment, which is completing the first production data run with the goal of equaling the experimental precision of the previous measurement with much better control and understanding of the systematic errors, and preparing for the upcoming data runs with the goal of improving the experimental precision by a factor of four. More specifically, the group has developed critical innovations for precision measurement of the magnetic field and its absolute calibration, and innovations in the most challenging aspect of the analysis of the field-measurement data, namely interpolating between calibration runs to track changes in the magnetic field and its spatial variations. The group will also complete commissioning and begin Nab, a new precision measurement of the beta-neutrino asymmetry parameter a in neutron decay that also probes physics Beyond the Standard Model by way of redundantly measuring the parameter lambda, the ratio of axial vector to vector coupling constants, which is also determined by the beta asymmetry (A). The neutron spin flipper designed and built at Michigan has been moved to the Fundamental Neutron Physics Beam (FNPB) at the SNS at ORNL. This will be used in determining the residual neutron beam polarization that would present a major systematic correction to the measurements. The He-3 magnetometer for absolute calibration developed and built by this group is fully operational, has sensitivity of sub ppb (part-per-billion) and will potentially impact precision magnetic field measurements from geology to medicine to physics. This research will continue to seed a number of outreach opportunities including public lectures on physics and its applications, undergraduate course development, lectures for specialist students such as the National Nuclear Physics Summer schools.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.