SuperCDMS Research and Development: WIMP Dark Matter Detector Performance, Scalability, and Surface Backgrounds

SuperCDMS 研究与开发：WIMP 暗物质探测器性能、可扩展性和表面背景

• 批准号: 0503729
• 负责人: Daniel Akerib
• 金额: --
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-11-01 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0503729&HistoricalAwards=false
• 关键词: SuperCDMS; Research; Development; WIMP; Dark

The discovery of dark matter is of fundamental importance to cosmology, astrophysics, high-energy particle physics and our understanding of gravity. A broad range of observations from galaxies and superclusters to distant supernovae and the cosmic microwave background radiation, tell us that nearly 90% of the matter in the universe is in some new form, different from ordinary particles. So far, going back to Zwicky's observations of the Coma cluster in the 1930's, this matter has revealed itself only through gravity, and is referred to as "dark matter" because it neither emits nor absorbs light. A leading hypothesis, which we propose to continue testing, is that the dark matter is comprised of Weakly Interacting Massive Particles, or WIMPs, a hypothetical elementary particle produced moments after the Big Bang in collisions of ordinary matter. If WIMPs are the dark matter, then their local density in our region of the Milky Way makes them detectable via scattering from atomic nuclei in a terrestrial detector. Natural WIMP candidates come from Supersymmetry (SUSY), an extension to the Standard Model (SM) of particle physics. Supersymmetric extensions of the SM solve a number of outstanding problems in particle physics, among them the so-called gauge hierarchy problem. These problems are completely distinct from riddles posed by astrophysics and cosmology. Perhaps not coincidently, SUSY particles have just the right properties to be the dark matter. The search for WIMP dark matter in the galactic halo and the large accelerator-based experiments at Fermilab's Tevatron and those under construction at CERN's Large Hadron Collider are, in a complementary fashion, searching for the same fundamental physics. Our group, as part of the Cryogenic Dark Matter Search (CDMS) collaboration, is conducting the CDMSII dark matter experiment which is currently running a 5-kg detector array in the Soudan Mine. The latest CDMSII result (July 2005) set the most stringent bound to date - by a factor of ten over all other experiments in the world - on the presence of WIMPs in the galactic halo, and has begun to constrain some of the parameter space where SUSY particles could lie. With support from this award, we will acquire a year of data with this full array, the analysis of which will allow an additional order of magnitude in sensitivity. Our group has plyaed a significant role in building the experiment using our detector test facility at Case, as well as building and operating the main apparatus at Soudan. In addition, have conducted background studies and data analyses that have been central to extracting the science. To date, four Case graduate students have completed their Ph.D.'s on the experiment, and currently two third year students on actively contributing to detector operations, Monte Carlo simulations and analysis. In the coming two years, these students, together with the PI's and research associates (postdocs), will continue travelling to the experimental site to tune up the new detector array, operate, and bring home the data to analyze. When at the mine, we will all participate in the active outreach program consisting of daily public tours of the laboratory. While the Soudan science effort will consume about 80% of the resources supported by this grant, we intend to use the remaining resources to carry out detector R&D aimed at a proposed next-generation experiment called SuperCDMS. This will primarily involve cryogenic testing of new detectors being fabricated by our DoE-supported collaborators at Stanford that aim to have improved rejection of backgrounds and higher mass per detector module. Within this testing program, we plan to take advantage of opportunities in which streamlined detector packaging and simpler cold electronics can be simultaneously tested. We will also continue thin film tungsten studies that were initiated last year through undergraduate senior projects. This work aims to better understand the properties of the temperature-sensitive films that detect particle interactions in our detectors. At present, there is a variability problem that can be corrected but requires significant testing resources. The preparation of the films is carried out at minimal cost in a shared departmental facility and tested in our dilution refrigerator simultaneously with detector-testing runs. The final aspect of our R&D work is to begin development of a new assay technique to detect low-energy beta emitters, which represent a background tha can hamper progress on the experiment. Using a modest level of resources and undergraduate involvement, we can help lay the groundwork for rapid progress in the future. The efforts of our group will be highly leveraged by the presence of Prof. T. Shutt's group at Case and Prof. S. Golwala's group at Caltech. Shutt's group is developing low-activity MWPC elements for the XENON experiment similar to what's needed for the beta screener, and Golwala's group may be in a position to provide hardware for prototype construction.

暗物质的发现对于宇宙学、天体物理学、高能粒子物理学和我们对引力的理解都具有根本的重要性。从星系和超星系团到遥远的超新星和宇宙微波背景辐射的广泛观测告诉我们，宇宙中近90%的物质以某种新的形式存在，不同于普通粒子。到目前为止，追溯到Zwicky在20世纪30年代对后发座星系团的观察，这种物质只能通过引力来揭示自己，并且被称为“暗物质”，因为它既不发射也不吸收光。 我们建议继续测试的一个主要假设是，暗物质由弱相互作用大质量粒子（WIMPs）组成，这是一种假设的基本粒子，在大爆炸后的普通物质碰撞中产生。如果WIMP是暗物质，那么它们在我们银河系区域的局部密度使得它们可以通过地面探测器中的原子核散射来检测。自然的WIMP候选者来自超对称性（SUSY），这是粒子物理学标准模型（SM）的扩展。SM的超对称扩展解决了粒子物理学中的一些突出问题，其中包括所谓的规范层次问题。这些问题与天体物理学和宇宙学提出的谜团完全不同。也许并非巧合，超对称粒子具有成为暗物质的正确属性。在星系晕中寻找WIMP暗物质，在费米实验室的Tevatron和正在欧洲核子研究中心的大型强子对撞机上进行的基于大型加速器的实验，都是以互补的方式寻找相同的基本物理。 作为低温暗物质搜索（CDMS）合作的一部分，我们的团队正在进行CDMSII暗物质实验，该实验目前正在苏丹矿运行一个5公斤的探测器阵列。最新的CDMSII结果（2005年7月）设定了迄今为止最严格的限制-比世界上所有其他实验高出10倍-在银河系晕中存在WIMP，并开始限制超对称粒子可能存在的一些参数空间。在该奖项的支持下，我们将获得一年的数据与这个完整的阵列，分析将允许一个额外的数量级的灵敏度。 我们的团队在使用我们在凯斯的探测器测试设施进行实验以及在苏丹建造和操作主要设备方面发挥了重要作用。此外，还进行了背景研究和数据分析，这对于提取科学知识至关重要。到目前为止，四个案例研究生已经完成了他们的博士学位。的实验，目前两个三年级的学生积极贡献探测器操作，蒙特卡罗模拟和分析。在接下来的两年里，这些学生将与PI和研究助理（博士后）一起继续前往实验地点，调整新的探测器阵列，操作并带回数据进行分析。在矿山时，我们都将参加积极的外联计划，包括每天对实验室的公开图尔斯参观。 虽然Soudan的科学工作将消耗这笔赠款支持的约80%的资源，但我们打算利用剩余的资源进行探测器研发，目标是拟议的下一代实验SuperCDMS。这将主要涉及由我们在斯坦福大学的能源部支持的合作者制造的新探测器的低温测试，旨在提高对背景的抑制和每个探测器模块的更高质量。在此测试计划中，我们计划利用简化的探测器包装和更简单的冷电子设备可以同时测试的机会。 我们还将继续薄膜钨的研究，去年开始通过本科高级项目。这项工作的目的是更好地了解温度敏感膜的性质，在我们的探测器中检测粒子相互作用。目前，有一个可变性问题，可以纠正，但需要大量的测试资源。薄膜的制备是在一个共享的部门设施中以最低的成本进行的，并在我们的稀释冰箱中与检测器测试运行同时进行测试。 我们研发工作的最后一个方面是开始开发一种新的检测技术来检测低能β发射体，这代表了可能阻碍实验进展的背景。利用适度的资源和本科生的参与，我们可以帮助奠定基础，在未来的快速发展。T教授的出席将极大地促进我们小组的努力。Shutt在Case和S.戈尔瓦拉在加州理工学院的团队Shutt的小组正在为XENON实验开发类似于beta筛选器所需的低活性MWPC元件，Golwala的小组可能能够为原型建造提供硬件。