Precision measurements of the decay products could indicate the presence of hypothesized sterile neutrinos.
The experiment involves implanting radioactive beryllium-7 atoms into superconducting sensors developed at LLNL and has been nicknamed the “BeEST†for “Beryllium Electron-capture with Superconducting Tunnel junctions.†When the beryllium-7 decays by electron capture into lithium-7 and a neutrino, the neutrino escapes from the sensor, but the recoil energy of the lithium-7 provides a measure of the neutrino mass.If a heavy sterile neutrino with mass mc2 were to be generated in a faction of the decays, the lithium-7 recoil energy would be reduced and produce a measurable signal, even though the elusive neutrino itself is not detected directly.
With a measurement time of just 28 days using a single sensor, the data excludes the existence of sterile neutrinos in the mass range of 100 to 850 kiloelectronvolts down to a 0.01 percent level of mixing with the active neutrinos — better than all previous decay experiments in this range.In addition, simulations on LLNL supercomputers have helped the team understand some of the materials effects in the detector that need to be accounted for to gain confidence in potential sterile neutrino detection events.
“Sterile neutrinos are exciting because they are strong candidates for so-called ‘warm’ dark matter, and they also may help to address the origin of the matter-antimatter asymmetry of the universe,†Friedrich said.Reference: “Limits on the Existence of sub-MeV Sterile Neutrinos from the Decay of 7Be in Superconducting Quantum Sensors” by S.June 11, 2021June 11, 2021June 11, 2021June 11, 2021June 10, 2021June 10, 2021