A Low-Threshold Analysis of Data from the Cryogenic Dark Matter Search Experiment
A Low-Threshold Analysis of Data from the Cryogenic Dark Matter Search Experiment
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低温暗物质搜索实验数据的低阈值分析
DOI：
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发表时间：
2011
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通讯作者：
R. Bunker
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作者：
R. Bunker
虽然暗物质似乎占宇宙物质的80%以上，但它的组成是一个谜。天体物理观测表明，银河系的发光部分嵌入在暗物质粒子的光环中。弱相互作用大质量粒子（WIMP）是研究最多的暗物质候选者，在许多弱尺度超对称理论的背景下自然产生。像低温暗物质搜索（CDMS）这样的直接探测实验致力于辨别WIMP与地球物质相互作用产生的反冲核的动能。这是一个相当大的挑战，其中必须将WIMP相互作用的低（预期）速率与由于已知类型的辐射造成的压倒性速率区分开来。一个无可争议的阳性检测仍然难以捉摸。然而，一些实验记录的数据似乎与低质量WIMP一致。本论文描述了一种尝试，探索有利的参数空间。为了提高对低质量WIMP的灵敏度，对小能量沉积具有改进灵敏度的低阈值技术被应用于CDMS浅场数据。2001年12月至2002年6月期间运行了四个锗探测器和两个硅探测器，产生了118天的暴露。通过牺牲一些CDMS探测器区分信号与背景的能力，三个锗探测器和两个硅探测器分别实现了~1和~2 keV的能量更多»阈值。观测到大量的WIMP候选事件，其中大部分可以解释为背景源的错误识别。没有发现低质量WIMP信号的确凿证据，用观测到的事件率来确定WIMP核子散射截面的上限。对于质量低于~ 9 GeV/c2的WIMP，不考虑有趣的参数空间。在标准假设下，将其他实验数据解释为低质量WIMP信号所青睐的参数空间被部分排除，并且新的参数空间被排除在3和4GeV/c2之间的WIMP质量之外。«少
Although dark matter appears to constitute over 80% of the matter in the Universe, its composition is a mystery. Astrophysical observations suggest that the luminous portions of the Galaxy are embedded in a halo of darkmatter particles. Weakly Interacting Massive Particles (WIMPs) are the most studied class of dark-matter candidates and arise naturally within the context of many weak-scale supersymmetric theories. Direct-detection experiments like the Cryogenic Dark Matter Search (CDMS) strive to discern the kinetic energy of recoiling nuclei resulting from WIMP interactions with terrestrial matter. This is a considerable challenge in which the low (expected) rate of WIMP interactions must be distinguished from an overwhelming rate due to known types of radiation. An incontrovertible positive detection has remained elusive. However, a few experiments have recorded data that appear consistent with a low-mass WIMP. This thesis describes an attempt to probe the favored parameter space. To increase sensitivity to low-mass WIMPs, a low-threshold technique with improved sensitivity to small energy depositions is applied to CDMS shallowsite data. Four germanium and two silicon detectors were operated between December 2001 and June 2002, yielding 118 days of exposure. By sacrificing some of the CDMS detectors’ ability to discriminate signal from background, energymore » thresholds of ~1 and ~2 keV were achieved for three of the germanium and both silicon detectors, respectively. A large number of WIMP candidate events are observed, most of which can be accounted for by misidentification of background sources. No conclusive evidence for a low-mass WIMP signal is found. The observed event rates are used to set upper limits on the WIMPnucleon scattering cross section as a function of WIMP mass. Interesting parameter space is excluded for WIMPs with masses below ~9GeV/c2. Under standard assumptions, the parameter space favored by interpretations of other experiments’ data as low-mass WIMP signals is partially excluded, and new parameter space is excluded for WIMP masses between 3 and 4GeV/c2.« less