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、高能粒子物理学和我们对引力的理解都是至关重要的。一种主要的假设是，暗物质是由弱相互作用的大质量粒子组成，即WIMP，这是一种超出粒子物理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，那么它们在银河系区域的局部密度可能使它们通过地球探测器中原子核的散射而被探测到。低温暗物质搜索(CDMS)在美国国家科学基金会和能源部的联合支持下，率先使用低温声子介导的探测器来区分此类WIMP在原子核上的罕见散射与显著的电子相互作用和放射性。使用我们在苏丹矿的强大技术，加上我们的高背景拒绝，CDMS是目前(7月5日)世界上最敏感的WIMP搜索实验，是十倍。该奖项提供的两年资金将主要用于支持索丹的CDMS II的运作，以便从我们现在安装的六个探测器的五个塔中尽可能地提取最好的科学。2006年1月从CDMS II基金接管，这笔国家科学基金的基础资金将使伯克利分校能够参与将CDMS延长至2007年6月，并参与对收集的数据的分析。这应该会使我们的原始敞口增加大约20倍，并将我们目前的敏感度提高10倍。伯克利的重点仍然是探测器性能的优化和持续的性能监测，改善电子噪声和进一步发展识别方法。基础资金还将支持实验室中探测器表征的适度努力，相信这将变得越来越有必要来证明我们的分析达到的歧视程度。我们还将投入大约20%的基础资金用于CDMS未来阶段的研发。这第二个组成部分对于维持CDMS在全球的领导地位和准备推论到更大的群众是必不可少的。伯克利的工作将分成以下几个部分：超级CDMS(总目标质量25公斤)A阶段探测器冷硬件的开发，斯坦福大学生产的A阶段探测器原型测试，以及超级CDMS B或C阶段(目标质量150公斤或更多)的动力学电感声子传感研究。这项建议将部分支持三名研究生的研究。我们的教育和外展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。对于后一项计划，我们已经与SMASH夏季学院达成合作，该学院为来自贫困背景的学业成绩优异的高中生提供支持。根据去年我们实验室一名九年级学生参与的试点项目，我们计划在本奖项期间每年招收两名学生学徒。

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.