Plutonium decay experiment seeks sterile neutrinos as dark matter candidate
Researchers at Lawrence Livermore National Laboratory are using plutonium-241 beta decays to search for sterile neutrinos, a hypothetical particle that could constitute warm dark matter. The Magneto-ν experiment precisely measures the decay products to infer the energy of the escaping antineutrino. Their initial results have been published in Physical Review C.
The Magneto-ν experiment operates at extremely low temperatures—0.01 Kelvin—using a dilution refrigerator to enable the magnetic microcalorimeter's precise energy readings. By capturing the combined energy of the emitted electron and the recoiling americium-241 atom, researchers reconstruct the antineutrino's energy without ever detecting it directly.
Plutonium-241's average beta energy of roughly 5 keV makes it well-suited for probing the kiloelectronvolt mass range where sterile-neutrino warm dark matter is theorized to exist. LLNL's unique combination of nuclear materials expertise, radiochemistry, and detector development enables this research, since plutonium is tightly controlled and few facilities can safely handle it for fundamental physics studies.
If the experiment confirms sterile neutrinos, it could reshape fundamental physics and cosmology, potentially explaining both dark matter's composition and the origin of neutrino mass. Such a discovery may influence future particle physics research priorities and astrophysical models. However, initial results are preliminary, and confirmation would require extensive verification. The societal impact is primarily scientific, though advances in microcalorimetry and precision measurement could eventually benefit other fields, including nuclear safeguards and medical imaging.