Experimental Particle Cosmology: Search for Dark Matter

从星系和超星系团到遥远的超新星，以及宇宙微波背景辐射的广泛观测，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组成的。破译这种暗物质的性质对于宇宙学、天体物理学、高能粒子物理学以及我们对引力的理解都具有根本的重要性。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，这是一种超越粒子物理学标准模型的基本粒子，但在各种扩展中被预测，如超对称性。如果WIMP是暗物质，那么它们在我们银河系的局部密度可能使它们通过地面探测器中原子核的散射而被探测到。由NSF和DOE联合支持的低温暗物质搜索（CDMS）合作组织率先使用低温声子介导的探测器来区分这种WIMP在核上的罕见散射和来自放射性的突出电子相互作用。CDMS在苏丹矿场使用了我们强大的技术，具有高背景抑制能力，是目前（2005年7月）世界上最灵敏的WIMP搜索实验，灵敏度为10倍。该奖项提供的两年资金将主要用于支持苏丹CDMS II的运行，以便从我们现在安装的五个塔的六个探测器中提取最佳科学。 从2006年1月的CDMS II资金接管，这个NSF的基础资金将允许伯克利参与CDMS运行到2007年6月的扩展和收集的数据的分析。这将使我们的原始曝光量增加大约20倍，并将我们目前的灵敏度提高10倍。伯克利的重点将仍然是优化的检测器性能和连续的性能监测，改善电子噪声和进一步发展的歧视方法。基础资金还将支持实验室中探测器特性的适度努力，这将被认为是越来越有必要的，以证明我们分析中达到的区分水平。我们还将投入大约20%的基础资金用于CDMS未来阶段的研发。这第二个组成部分是必不可少的，在保持CDMS的领导地位在世界范围内，并准备外推到更大的群众。伯克利的工作将分为SuperCDMS A阶段（总目标质量为25公斤）探测器的冷硬件开发，斯坦福大学生产的A阶段探测器原型的测试和SuperCDMS B或C阶段（目标质量为150公斤或更高）的动力学感应声子传感研究。我们的教育和推广活动将侧重于改善苏丹科学图尔斯之旅的展示和东湾高中学生的学徒计划。 对于后一个项目，我们已经与SMASH暑期学院合作，该学院为来自服务不足背景的高中学生提供学术支持。根据去年的试点计划，涉及他们的九年级学生在我们的实验室之一，我们计划有两个学生学徒，每年在此期间的奖励。

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.