Schematic of the “BeEST” experiment. Radioactive beryllium-7 is implanted into the superconducting sensor. Precision measurements of the decay products could indicate the presence of hypothesized sterile neutrinos.
Schematic of the “BeEST” experiment. Radioactive beryllium-7 is implanted into the superconducting sensor. Precision measurements of the decay products could indicate the presence of hypothesized sterile neutrinos.
Image credit: Spencer Fretwell, Colorado School of Mines

The Science

An international team has performed one of the world’s most sensitive laboratory searches for a subatomic particle called the “sterile neutrino.” These hypothetical particles may explain dark matter. They may also explain why the Universe contains more matter than antimatter. The novel experiment uses radioactive beryllium-7 atoms created at the TRIUMF facility in Canada. The research team then implants these atoms into sensitive superconductors cooled to near absolute-zero.

The Impact

One of the biggest mysteries in science is the nature of dark matter. Dark matter makes up approximately 85 percent of the mass in the Universe. This novel experiment does not search for dark matter particles directly. Instead, it measures the signature from atoms produced in certain radioactive decays. Specifically, it looks for the energy of lithium-7 from the decay of beryllium-7. This decay would be affected by sterile neutrino dark matter particles. This effect can be measured when researchers implant the beryllium-7 into superconducting quantum sensors. This powerful new approach also enables other experiments in nuclear science.

Summary

The Beryllium Electron capture in Superconducting Tunnel junctions (BeEST) experiment is a new search for sterile neutrinos using precision measurements of the electron capture decay of beryllium-7. The approach uses superconducting tunnel junction quantum sensors. This is a powerful experimental method since it relies only on the well-motivated existence of this new type of particle, not on how the particle might hypothetically interact with normal matter. The research is conducted by an international research team led by the Colorado School of Mines and Lawrence Livermore National Laboratory. The team has performed the first measurements in the BeEST experimental program using a single superconducting quantum sensor counting at a low rate for one month. This initial work already excludes the existence of these particles up to 10 times better than all previous decay experiments. The demonstration of this concept will allow the research team to provide even more powerful searches for these new particles using large arrays of sensors with new superconducting materials.

Contact

Kyle G. Leach
Colorado School of Mines
kleach@mines.edu

Stephan Friedrich
Lawrence Livermore National Laboratory
friedrich1@llnl.gov

Funding

This work was funded by the Department of Energy Office of Science, Office of Nuclear Physics, by the Laboratory Directed Research and Development program at Lawrence Livermore National Laboratory, and the Natural Sciences and Engineering Research Council of Canada. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. This research was performed under appointment to the Nuclear Nonproliferation International Safeguards Fellowship Program sponsored by the Department of Energy, National Nuclear Security Administration’s Office of International Nuclear Safeguards. This work was performed under the auspices of the Department of Energy by Lawrence Livermore National Laboratory.

Publications

Friedrich, S., et al. Limits on the Existence of sub-MeV Sterile Neutrinos from the Decay of 7Be in Superconducting Quantum Sensors. Physical Review Letters 126, 021803 (2021). [DOI: https://doi.org/10.1103/physrevlett.126.021803]

Related Links

Mines researchers on the hunt for “ghost particles” with quantum sensors, Colorado School of Mines Newsroom

Hunting with the BeEST: PRL paper establishes new boundaries in search for sterile neutrinos, TRIUMF News: Headlines and Research Highlights