Speaker
Description
The BeEST (Beryllium Electron capture in Superconducting Tunnel junctions) experiment searches for keV-scale sterile neutrinos via high precision measurements of eV-scale nuclear recoils and energy-momentum reconstruction method in the electron capture (EC) decay of $^{7}$Be. $^{7}$Be atoms are directly implanted into superconducting tunnel junction (STJ) sensors that can measure the energy of $^{7}$Li daughter recoils with a few-eV precision. We have measured a high-statistics $^{7}$Li recoil spectrum with a single pixel for 30 days, and excluded sterile neutrino mixing for |Ue4|2 > 0.0002 at 90% confidence level in the 100 keV mass region. This is an order of magnitude better than results from previous experiments. In the full-scale BeEST experiment, the statistical precision to the sterile neutrino mixing |U$_\rm{e4}$|$^{2}$ will approach O(10$^{-7}$) levels with increased number of pixels and a higher dose of 7Be. To improve systematic uncertainties, we are improving our 7Be spectrum model using preliminary multi-pixel data. Our experimental approach, analytical methods, and projected experimental sensitivities will be presented.
| Collaboration | BeEST Collaboration |
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