A Search for Sterile Neutrino Dark Matter
Stephan Friedrich | 20-LW-006
Decades of dark matter searches with increasingly higher sensitivity have so far not been able to detect the most-favored hypothetical dark-matter particles. This has increased interest in sterile neutrinos with masses in the kilo- to electronvolt (keV) range as possible dark matter candidates. We have established a new and world-leading approach to search for keV-scale sterile neutrinos with superconducting radiation detectors. We implanted radioactive beryllium-7 (Be-7) nuclei into our superconducting tunnel junction (STJ) detectors and measured the recoil energy of the lithium-7 (Li-7) daughter nucleus with high accuracy. If the associated electron-neutrino wave function contains some admixture of a keV sterile flavor, the Li-7 recoil energy will be shifted and produce an additional peak in the spectrum whose energy depends on the sterile-neutrino mass. While we have not observed any evidence for sterile neutrinos in these precision-decay experiments, the experiment has increased the sensitivity of sterile-neutrino searches by a factor of ~10 over competing approaches in the mass range from ~10 to ~800 keV. The next generation of STJ detectors that we developed as part of this project will be able to further increase the sensitivity of the sterile-neutrino search by at least another two orders of magnitude.
This project has established a Nobel-caliber experiment with the potential to solve one of the great open questions in cosmology and particle physics. The same approach of integrating radioactive material into quantum sensors operated at ultra-low temperatures can also be used for accurate measurements of uranium and plutonium samples to improve nuclear safeguards and advance nonproliferation. We are currently developing the technology to provide this capability to the International Atomic Energy Agency (IAEA).
Publications, Presentations, and Patents
Friedrich, S. et al., 2021. "Limits on the Existence of Sub-MeV Sterile Neutrinos from the Decay of Be-7 in Super-Conducting Quantum Sensors." Physics Review Letters 126, 021803 (2021). https://doi.org/10.1103/PhysRevLett.126.021803.
Leach, K. G. and S. Friedrich. 2022. "The BeEST Experiment: Searching for Beyond Standard Model Neutrinos Using Be-7 Decay in STJs. Journal of Low Temperature Physics 209, 796-803 (2022). https://doi.org/10.1007/s10909-022-02759-z.
Bray, C. E. et al., 2022. "Monte Carlo Simulations of Superconducting Tunnel Junction Quantum Sensors for the BeEST Experiment." Journal of Low Temperature Physics 209, 857-863 (2022). https://doi.org/10.1007/s10909-022-02770-4.
Friedrich, S. et al., 2022. "Characterization of Non-Uniformities in Superconducting Tunnel Junction Radiation Detectors." Journal of Low Temperature Physics 209, 1063-1069 (2022). https://doi.org/10.1007/s10909-022-02825-6.
Samanta, A. et al., 2023. "Material Effects on Electron-Capture Decays in Cryogenic Sensors." Physics Review Applied 19, 014032 (2022). https://doi.org/10.1103/PhysRevApplied.19.014032}.