MRI Consortium: Development of a Room-Temperature Apparatus to Measure the Electric Dipole Moment of the Neutron, for a Fast-track Ten-fold Improvement in Sensitivity

University Of Kentucky Research Foundation, Lexington KY

Investigators

Abstract

This award supports the building of a new experiment at the Los Alamos National Laboratory (LANL) that will be sensitive to a neutron electric dipole moment at a very small scale. Neutrons are subatomic particles and, along with the proton, are the basic constituents of atomic nuclei. They are electrically neutral, but nothing in principle prevents the neutron from having positive and negative poles, a so-called "electric dipole moment"(EDM). Big-bang theories of the origin of the universe predict that matter and antimatter are created in equal parts, which should have annihilated long ago. The current observable universe has much more matter than antimatter, thus there should be processes which caused this imbalance in the evolution of the cosmos. These mechanisms require the behavior of matter and antimatter to be slightly different from each other's mirror image. The same underlying mechanism also predicts that the neutron should have an EDM large enough to be observable. Thus, neutron EDM experiments attempt to shed light on the question as to why there is any matter in the universe at all. This award supports the construction of instrumentation needed to improve the sensitivity to the nEDM by a factor of ten beyond current limits, taking advantage of the increased ultracold neutron (UCN) yield from the upgraded UCN source at LANL. In developing the knowledge and technical basis needed for the nEDM search, students and postdoctoral researchers will become the next generation of scientists. Experimental searches for the neutron electric dipole moment (nEDM) have been conducted since 1951. To date, no evidence for an nEDM has been found. In many theoretical scenarios, successful matter creation leads to strict lower bounds on the nEDM on the order of 10^-27 e-cm. If no nEDM is discovered, this experiment, in combination with ongoing EDM searches in atomic and nuclear systems, will push the limits on the mass scale for new symmetry violating physics above 100 TeV. This exceeds the current and future energy reach of the Large Hadron Collider. On the other hand, discovery of a nonzero nEDM at this level would reveal a completely new source of symmetry violations, contributing to the development of a unified theory of the fundamental forces of nature that is consistent with cosmology. Achieving the target nEDM sensitivity requires high densities of polarized ultra-cold neutrons (UCN) and an apparatus capable of controlling systematic effects. The experiment design is based on Ramsey's method of separated oscillatory fields using a two-cell measurement chamber, state-of-the-art magnetic shielding, novel magnetic field configurations, and sensitive magnetometry (both external and co-habitating) to control systematics. This room-temperature design (unlike many cryogenic designs under development) will allow the instrument to be assembled, tested, and commissioned on a three-year timescale. The development is leveraged by the existing technical strengths of Indiana University, the University of Kentucky, LANL, the University of Michigan, and Yale University. This project will partner with the private sector to build a magnetically shielded space for the experiment, atomic magnetometers, and improve magnetic resonance measurements which may have an impact on medical imaging technology. 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.