EAGER-New Search Technique for keV Sterile Neutrinos

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The nature of dark matter is one of the most important questions in physics today, and the massive sterile neutrino is an excellent candidate. Earlier searches have produced excellent sensitivities for masses between 20 and 300 MeV/c^2; however, the mass range between a few keV/c^2 and one MeV/c^2 is of great interest as candidates for both cold and warm dark matter. A few searches have been made in this mass range; however, the branching ratio sensitivities have only been between 10^-3 and 10^-4, while the mass range below 200 keV/c^2 is almost unexplored. The experiment being planned here is designed to test the effectiveness of the experimental technique to explore this entire region with branching ratio sensitivities on the order of 10^-6. The PI is collaborating with the University’s College of Engineering in detector development. The ideal detector geometry at the focus of the Gerholm spectrometer is conical. The available conical detectors are plastic scintillators coupled to avalanche photodiodes. The team will explore the development of a conical solid-state detector with fast response. The PI’s Engineering colleagues have already produced excellent planar silicon carbide (SiC) detectors for x-rays. Together they want to develop techniques to deposit the active detector material on a conical sub-straight to create a high-resolution electron detector with the ideal geometry for the spectrometer. There are many other potential applications for particle detectors deposited on curved surfaces.If this pilot program is successful in demonstrating that radioactive sources with very small beta-decay branches can be measured with this spectrometer, this technique could be applied in a larger second-generation experiment to reach branching ratios of ~10^-8. The funds awarded will be used to demonstrate the efficacy of a newly developed technique in beta spectroscopy to search for sterile neutrinos with a recently reconfigured high-transmission Gerholm beta spectrometer. The funds will also provide for a data acquisition system, radioactive sources, machine shop services and graduate student support to perform a pilot search.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.