Searching for sterile neutrinos using radioactive levitated nanoparticles

The repeated measurements of neutrino oscillations over the last few decades confirm that neutrinos have non-zero masses which are not accounted for in the Standard Model. The observed small neturino masses can be explained by introducing a massive right-handed "sterile neutrino" that does not interact through the weak force. One class of experiments searching for sterile neutrinos utilise radioactive decays to generate neutrinos and search for deviations in the recoil energy spectra of the daughter nucleus that would suggest mixing between Standard Model neutrinos and a sterile neutrino. We present a new experiment that is currently being realised that utilises levitated nanoparticles doped with a radioactive isotope to measure the momentum of the recoiling daughter nucleus and reconstruct the momentum of the emitted neutrino. Measuring momentum rather than energy significantly reduces the impact of low or zero mass backgrounds and secondary emissions. This search will improve sensitivity to sterile neutrinos in the mass range 100 keV - 2 MeV compared to previous experiments. Interestingly, a sterile neutrino within this mass range could explain almost all observed dark matter.