Torsion-Balance Searches for Ultra-Light Dark Matter

天体物理观测和宇宙学数据提供了强有力的证据，证明宇宙近四分之一由暗物质组成。有充分的理由相信它不可能由已知粒子组成。暗物质很可能是由新粒子组成的，这些新粒子还没有在任何其他环境中暴露出来。暗物质粒子有两种很好的可能性：称为WIMP的重费米子粒子和玻色子超轻暗物质（ULDM），轴子是其中的一个子集。目前，用于WIMP的大型设施尚未发现暗物质。最近的理论建议激发了对质量低至10^（-23）eV/c2的ULDM粒子的研究。这些粒子不是单独检测到的，而是通过它们产生的相干场来检测的，这在小规模精密实验中最容易检测到。由Eöt-Wash重力集团开发的扭转平衡技术非常适合搜索这些玻色子场的预期效应。该小组有着悠久的教学研究的传统，本科生，研究生和博士后。通过正式和非正式的教学，该项目将在各个层面提供广泛的STEM教育。该项目提供了基础物理学，精密机械仪器的实现和精密测量的执行方面的独特培训机会。该技术的发展正在应用于引力波探测以及地震学等应用领域。扭力天平已经变得足够灵敏，成为寻找ULDM的重要工具。最近，这样的测量设置了一些最严格的限制类轴子和等效原理违反ULDM。在技术进步的推动下，这种扭力平衡搜索将包括对现有仪器的升级，使这些暗物质搜索更加灵敏。此外，将进行数据分析，以寻找违反等效原理的玻色ULDM的签名，在并发扭转平衡测试的重力数据流。该奖项将资助使用旋转和固定扭转天平搜索这种玻色子ULDM，使用铍和聚乙烯测试材料来提高ULDM的灵敏度;使用升级后的固定扭转天平中现有的独特自旋极化扭转摆来搜索自旋耦合类轴子ULDM;并通过改进熔融石英光纤、增加辅助传感器、升级读数，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Astrophysical observations and cosmological data give strong evidence that nearly a quarter of the Universe consists of dark matter. There are strong reasons to believe that it cannot consist of known particles. It is likely that the dark matter consists of new particles that have not yet revealed themselves in any other context. There are two well-motivated possibilities for the dark-matter particles: heavy fermionic particles called WIMPs and bosonic ultra-light dark matter (ULDM), of which axions are a subset. Searches at large-scale facilities for WIMPs have not yet found dark matter. Recent theoretical suggestions have inspired searches for ULDM particles with masses as low as 10^(-23) eV/c2. These particles are not detected individually, but rather by the coherent fields they produce, which are most-readily detected in small-scale precision experiments. The torsion balance technology developed by the Eöt-Wash Gravity Group is ideally suited to search for the effects expected from these bosonic fields. The group has a long tradition of teaching research to undergraduate students, graduate students, and postdocs. With formal and informal instruction this project will provide broad STEM education at all levels. This project offers unique training opportunities in fundamental physics, realization of precision mechanical instruments, and the execution of precision measurements. The technology developed is finding application in gravitational wave detection as well as in applied areas such as seismology.Torsion balances have become sensitive enough to be significant tools in the search for ULDM. Recently, such measurements have set some of the most stringent limits on axion-like and equivalence-principle-violating ULDM. Enabled by technological advances, this torsion balance search will encompass upgrades to existing instruments that make these dark matter searches substantially more sensitive. In addition, data analysis will be performed to look for the signature of equivalence-principle-violating bosonic ULDM in the data stream of concurrent torsion-balance tests of gravity. This award will fund searches for this bosonic ULDM using rotating and stationary torsion balances, using beryllium and polyethylene test materials to increase ULDM sensitivity; searches for spin-coupled axion-like ULDM using an existing unique spin-polarized torsion pendulum in an upgraded stationary torsion balance; and increase experimental sensitivity to ULDM signals by refining fused-silica fibers, adding auxiliary sensors, upgrading readout, and improving instrumental shielding.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.