EAGER-New Search Technique for keV Sterile Neutrinos

暗物质的性质是当今物理学中最重要的问题之一，而大质量的不育中微子是一个很好的候选者。早期的搜索对质量在20到300 MeV/c^2之间产生了极好的灵敏度；然而，在几keV/c^2到1 MeV/c^2之间的质量范围作为冷暗物质和热暗物质的候选者都引起了极大的兴趣。在这个质量范围内已经进行了一些研究，然而，分支比灵敏度只在10^-3到10^-4之间，而在200keV/c^2以下的质量范围几乎没有被探索过。这里计划进行的实验旨在测试实验技术的有效性，以探索分支比灵敏度在10^-6数量级的整个区域。PI正在与该大学的工程学院合作开发探测器。格霍尔姆光谱仪焦点处的理想探测器几何形状是圆锥形。可用的锥形探测器是耦合到雪崩光电二极管的塑料闪烁体。该团队将探索开发一种具有快速响应的锥形固态探测器。PI的工程部同事已经生产出了用于X射线的出色的平面碳化硅(SIC)探测器。他们希望共同开发技术，将活跃的探测器材料沉积在锥形次直线上，以创造出具有光谱仪理想几何形状的高分辨率电子探测器。沉积在曲面上的粒子探测器还有许多其他潜在的应用。如果这一试点计划成功地证明了可以用该谱仪测量具有非常小的β衰变分支的放射源，则该技术可以应用于更大的第二代实验，以达到~10^-8的分支比。授予的资金将用于展示一项新开发的贝塔光谱学技术的有效性，该技术利用最近重新配置的高透射率格霍尔姆贝塔光谱仪来搜索无菌中微子。这笔资金还将用于数据获取系统、放射源、机械修理厂服务和研究生支持，以进行试点搜索。这一奖励反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.