BEEST FOR THE GENERAL PUBLIC
General BeEST Information
The search for sterile neutrinos is perhaps the brightest possibility in our quest for understanding the microscopic nature of the observed dark matter (DM) in our Universe. Sterile neutrinos – unlike the active neutrinos in the Standard Model – do not interact with normal matter as they move through space, and are thus best observed using their mass signature. In this work, complete momentum reconstruction of electron-capture (EC) nuclear decay is employed to perform a search for sterile neutrinos in the keV mass range that is 10,000 times more sensitive than previous experiments. This is achieved using the EC decay of radioactive beryllium-7 atoms implanted into sensitive superconducting tunnel junctions (STJs) – an experiment nicknamed the BeEST (beast) for Beryllium Electron capture in STjs. A discovery signature in the BeEST experiment would be a small fraction of these decays where the daughter (lithium-7) atomic recoil peaks are shifted to lower energies from momentum conservation with these new, heavy sterile neutrinos. This approach is a uniquely powerful experimental method since it relies only on the well-motivated existence of this new type of neutrino, and not on how they might hypothetically interact with normal matter.