Experimental Particle Cosmology: Search for Dark Matter

广泛的观测——从星系和超星系团到遥远的超新星，再到宇宙微波背景辐射——都给出了一致的结果——告诉我们，宇宙中大约85%的物质不是由普通粒子构成的。破译这种暗物质的本质对宇宙学、天体物理学、高能粒子物理学和我们对引力的理解都至关重要。一个主要的假设是暗物质是由弱相互作用大质量粒子（wimp）组成的，wimp是一种超出粒子物理学标准模型的基本粒子，但在各种扩展中被预测，比如超对称。如果wimp是暗物质，那么它们在我们银河系区域的局部密度可能会使它们通过地球探测器的原子核散射而被探测到。低温暗物质搜索（CDMS）合作，由美国国家科学基金会和美国能源部联合支持，率先使用低温声子介导的探测器来区分这种wimp在原子核上的罕见散射和突出的电子相互作用。利用我们在苏丹矿山的强大技术，加上我们的高背景抑制，CDMS是目前（7月05日）世界上最敏感的WIMP搜索实验，以十倍的速度。该奖项提供的两年资金将主要用于支持在苏丹的CDMS II的运作，以便从我们现在安装的五个由六个探测器组成的塔中提取尽可能最好的科学。从2006年1月的CDMS II基金中接管，NSF的基础基金将允许伯克利参与CDMS的扩展，该扩展将持续到2007年6月，并对收集的数据进行分析。这将使我们的原始曝光增加大约20倍，并将我们当前的灵敏度提高10倍。伯克利的重点将仍然是探测器性能的优化和连续性能监测，电子噪声的改进和进一步发展的鉴别方法。基础资金还将支持实验室中检测器表征的适度努力，这将越来越有必要证明我们分析中达到的区分水平。我们还将把大约20%的基础资金用于CDMS未来阶段的研发。第二个组成部分对于保持CDMS在全球的领导地位和为推广到更大的群体做准备是必不可少的。伯克利的工作将分为三个部分：开发SuperCDMS A相探测器的冷硬件（总目标质量为25kg），斯坦福大学生产的A相探测器原型的测试，以及研究SuperCDMS B或C相的动态电感声子传感（目标质量为150 kg或更多）。本提案将部分支持三位研究生的研究。我们的教育和推广活动将集中在改善苏丹科学之旅的展示和东湾高中生的学徒计划上。对于后一个项目，我们已经与SMASH暑期学院合作，该学院支持来自服务不足背景的学术高中生。根据去年的试点项目，其中包括一名九年级学生在我们的实验室，我们计划在本奖项期间每年有两名学生学徒。

A broad range of observations-from galaxies and superclusters to distant supernovae, and the cosmic microwave background radiation, all giving consistent results-tells us that about 85% of the matter in the universe is not made of ordinary particles. Deciphering the nature of this dark matter would be of fundamental importance to cosmology, astrophysics, high-energy particle physics, and our understanding of gravity. A leading hypothesis is that dark matter is comprised of Weakly Interacting Massive Particles, or WIMPs, an elementary particle beyond the Standard Model of particle physics, but predicted in various extensions, such as supersymmetry. If WIMPs are the dark matter, then their local density in our region of the Milky Way potentially makes them detectable via scattering from atomic nuclei in a terrestrial detector.The Cryogenic Dark Matter Search (CDMS) Collaboration, supported jointly by NSF and DOE, has pioneered the use of low temperature phonon-mediated detectors to distinguish the rare scattering of such WIMPs on nuclei from the prominent electron interactions from radioactivity. Using our powerful technology in the Soudan mine, with our high background rejection, CDMS is currently (July 05) the most sensitive WIMP search experiment in the world, by a factor of ten. The two years of funding provided by this award, will mainly support the operation of CDMS II at Soudan in order to extract the best science possible from the five towers of six detectors that we now have installed. Taking over from the CDMS II funding in January 2006, this NSF base funding will allow Berkeley to participate in the extension of CDMS running till June 2007 and in the analysis of the data collected. This should allow us to multiply our raw exposure by roughly a factor twenty and improve our current sensitivity by a factor ten. Berkeley's emphasis will remain the optimization of the detector performance and continuous performance monitoring, improvement of the electronic noise and further development of discrimination methods. The base funding will also support a modest effort of detector characterization in the laboratory, which will believe will become increasingly necessary to demonstrate the discrimination level reached in our analyses.We will also devote approximately 20% of the base funding to R&D for the future stages of CDMS. This second component is essential in maintaining the CDMS leadership worldwide and prepare for extrapolation to larger masses. The Berkeley effort will be divided between the development of the cold hardware for the detectors of the phase A of SuperCDMS (25kg total target mass), the test of phase A detector prototypes produced by Stanford and the study of kinetic inductance phonon sensing for the phase B or C of SuperCDMS (150 kg target mass or more).This proposal will partially support the research of three graduate students. Our education and outreach activity will focus on the improvement of the displays for the science tours at Soudan and on the apprenticeship program for East Bay High-School students. For the latter program, we have entered into collaboration with the SMASH summer academy, which supports academically high school students from underserved backgrounds. Based on last years pilot program involving one of their 9th Grade students in our laboratory, we are planning to have two student apprentices per year over the duration of this award.