Collaborative Research: Axion Resonant InterAction Detection Experiment (ARIADNE) - a Renewal Proposal

Northwestern University, Evanston IL

Investigators

Abstract

The Standard Model of particle physics provides the most current accurate description of the fundamental particles and forces at the subatomic scale. As successful as the Standard Model has proven to be, it is known to be incomplete, requiring extensions to incorporate new elements including particulate dark matter. Axions are hypothesized particles that appear in many extensions of the particle physics Standard Model, including the well-motivated Peccei-Quinn (PQ) theory. The PQ axion may provide explanations for both the anomalous smallness of the measured neutron electric dipole moment, and is also a promising dark matter candidate. The Axion Resonant InterAction DetectioN Experiment (ARIADNE) is designed to search for axion-mediated spin-dependent interactions between nuclei at sub-millimeter ranges. This award supports the collaborative research team to complete the development and construction and initiate operation of the ARIADNE experiment. The unique approach provides the proposed team of postdoctoral, graduate, and undergraduate researchers with a broad training in the techniques of experimental atomic physics, optical pumping, nuclear magnetic resonance, low-temperature physics, micro-fabrication, magnetic shielding, vacuum systems, and modeling. This breadth of expertise will be valuable preparation for opportunities in basic or applied research in the U.S. work force or scientific community. The experimental program involves a diverse group of young career researchers with an emphasis on broadening participation of under-represented groups. In addition, searching for dark matter is a topic with broad public appeal, and the group is involved in local outreach efforts. Axions and axion-like particles also generate macroscopic P-odd and (Time Reversal) T-odd spin-dependent interactions which can be sought in sensitive laboratory experiments. The ARIADNE experiment involves a rotating non-magnetic mass to source the axion field, and a dense ensemble of laser-polarized 3He nuclei to detect the axion field by NMR (nuclear magnetic resonance). The signal from an axion field can be resonantly enhanced by properly modulating the axion potential at the nuclear spin precession frequency. With the start of the data taking stage, new parameter space for the PQ axion and axion-like particles will be explored. In contrast to cosmic axion searches, since the experiment sources the axion field using local matter, this setup is sensitive to the axion even if it does not make up most of the dark matter. Furthermore, by sensing the axion's coupling to nuclei, an entirely complimentary coupling is probed to that sought by Sikivie-type microwave cavity “haloscope'' experiments and their proposed lower- and higher-frequency extensions. 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.