Dusel R&D: A Multiplicity Meter for Benchmarking Cosmogenic Neutron Backgrounds for Underground Experiments

暗物质的性质是粒子物理、宇宙学和天体物理学中最重要的悬而未决的问题之一。一个主要的假设是，弱相互作用的大质量粒子，或称WIMP，是在早期宇宙中产生的，组成了暗物质。到目前为止，人们只能通过引力效应观察到这种物质。弱者不可能是标准模型粒子，因此他们的发现将为一种新的物质形式欢呼。探测还将有助于解开宇宙学中一个长期存在的谜团，这个谜团甚至质疑我们对引力的理解。暗物质集中在包括银河系在内的星系的光晕中。如果WIMP组成了这些晕，它们可以通过地下探测器中原子核的散射被探测到。地下实验室中快中子的核反冲是WIMP探测最具挑战性的背景之一。这一背景的比率目前还没有得到很好的量化。在这项提案中，要求为一项便携式试验提供资金，该试验将通过在苏丹矿2000米水当量的深度下运行至少一年，将采矿率控制在10%左右。长期使用的液体闪烁体技术将被用于在铅辐射体附近安装中子多重数计，类似于实际暗物质实验中的屏蔽。所有暗物质实验以及许多其他地下实验都依赖于中子背景环境的知识。能够以更可靠的方式预测这个背景将很好地服务于这个社区，并为未来旨在更深地点运行的实验提供改进的外推。

The nature of dark matter is one of the most important outstanding issues in particle physics, cosmology and astrophysics. A leading hypothesis is that Weakly Interacting Massive Particles, or WIMPs, were produced in the early universe and make up the dark matter. So far this matter has only been observed through its gravitational effects. WIMPs cannot be Standard Model particles and so their discovery would hail a new form of matter. A detection would also help solve a long-standing riddle in cosmology that even questions our understanding of gravity. Dark matter is concentrated in the halos of galaxies, including the Milky Way. If WIMPs make up these halos they can be detected via scattering from atomic nuclei in an underground detector.Nuclear recoils from fast neutrons in underground laboratories are one of the most challenging backgrounds to WIMP detection. The rate of this background is at present poorly quantified. In this proposal, funds are requested for a portable experiment that will pin down their rate to about 10% by operating it in the Soudan Mine for a period of at least one year at a depth of 2000 meters of water equivalent. The long-used technique of gadolinium-loaded liquid scintillator will be employed to implement a neutron multiplicity meter adjacent to a lead radiator," similar to the shielding in an actual dark matter experiment. All dark matter experiments, as well as many other underground experiments, rely on knowledge of the neutron background environment. Being able to predict this background with greater reliability will serve well this community, and provide improved extrapolations for experiments aiming to operate in deeper sites in the future.