The BeEST Experiment: Searching for Beyond Standard Model Neutrinos using $^7$Be Decay in STJs

Understand

Precision measurements of nuclear $\beta$ decay are among the most sensitive methods to probe beyond Standard Model (BSM) physics in the neutrino sector.

• In particular, momentum conservation between the emitted decay products in the final state is sensitive to any massive new physics that couples to the neutrino mass.
• One way to observe these momentum recoil effects experimentally is through high-precision measurements of electron-capture (EC) nuclear decay, where the final state only contains the neutrino and a recoiling atom.
• The BeEST experiment precisely measures the eV-scale radiation that follows the radioactive decay of $^7$Be implanted into sensitive superconducting tunnel junction (STJ) quantum sensors.