Light Axion Dark Matter Search Using Toroidal Ferrite

Trustees Of Boston University, Boston

Investigators

Abstract

Dark matter is arguably the most compelling evidence of physics beyond the Standard Model. Since dark matter has only been observed through its gravitational effects, there is a wide range of possible dark matter candidates, and a large number of direct and indirect searches for dark matter interactions with standard model particles. Axions and axion-like particles are prominent dark matter candidates: they are predicted to exist by string-theory-inspired extensions of the Standard Model, are hinted at by a number of astrophysical phenomena, and, in the case of the QuantumChromoDynamic axion, offer an elegant solution to the strong-Charge-Parity problem. In addition, discovery of light axion-like dark matter may provide insights into the earliest epochs of the universe, specifically the energy scale of inflation. The experimental search funded by this award has the potential to shed light on these important puzzles. This award integrates research and outreach by developing a program designed to spark interest in science among young students and the general public, and to teach problem solving skills and strategies that are better-suited to complex real-world challenges. This program will include creating a collection of non-standard conceptual physics problems that will be made available to physics educators and the broad public via the world-wide-web. This award will provide funds for a direct experimental search for light axion dark matter, via the axion-photon interaction. This interaction between axion dark matter and the azimuthal magnetization of a magnetized ferrite toroid creates an axial magnetic field, oscillating at the axion Compton frequency. A SQUID magnetometer is inductively coupled to the sample in order to detect this field. Both non-resonant and resonant coupling schemes will be explored, in order to find the optimal search strategy for this experimental design. The apparatus will be placed inside a liquid helium cryostat, and superconducting magnetic shielding will be used to screen external electromagnetic interference. The experiment targets a very broad range of axion masses between ~ 10^-16 eV and 10^-8 eV. The experimental sensitivity reach extends several orders of magnitude beyond existing bounds on axion-photon interaction, exploring the range of couplings that are favored by a number of astrophysical observations, such as the transparency of the universe to TeV photons. 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.