利用PandaX液氙探测器寻找低质量暗物质

发布时间：2018-02-14 10:31

本文关键词： 暗物质二相型液氙时间投影室 PandaX　出处：《上海交通大学》2015年博士论文　论文类型：学位论文

【摘要】：众多的天文观测与大尺度结构模拟都显示有宇宙间暗物质存在的证据。在近三十年间被称为WIMP(弱相互作用重粒子)的粒子因其能够匹配现今宇宙的暗物质密度,在暗物质直接探测领域得到了广泛关注。在现今的暗物质直接探测技术中,使用液氙作为探测介质的二相型时间投影室技术(LXe-TPC)是目前最为主流的一项探测技术。其主要优势在于对伽马本底很好的辨别排除能力,以及高质量的事例三维重建能力。二相型液氙时间投影室的高本底排除效率源于在液氙中伽马本底产生的电子反冲和暗物质可能产生的核反冲间电离与闪烁信号比例的差异。目前对于液氙中的低能信号响应模型并没有达到可靠的精度。其中需要完善的有在低能区(几ke V)电子反冲的光子电子产生率,以及对伽马本底排除率极限的相关问题。在本论文第三章中将介绍一套小型二相型液氙时间投影室的开发与构建,涵盖对其真空制冷、气液循环、数据采集和数据分析系统的介绍。所研发的探测器在试运行中得到了较高的能量分辨率,适合用于研究液氙中低能量的电子和核反冲信号。本论文将在第四章中详细阐述使用该小型二相型液氙时间投影室探测低能反冲信号的过程,以及我通过所得数据构建的信号模型。该信号模型更新了已有模型中对于低能电子反冲以及液氙中反冲分辨能力上理解的不足。测量结果对利用液氙探测器寻找暗物质可能产生的电子反冲信号[1,2]起到了参考作用。同时也为下一代液氙探测器的优化给出了方向。本论文在第五章中将详细介绍Panda X暗物质直接探测实验的数据分析。Panda X是中国第一个使用二相型液氙时间投影室技术的暗物质直接探测实验。它坐落于拥有目前世界最低宇宙线本底的四川锦屏地下实验室CJPL(6900多米等效水深)。Panda X一期探测器利用扁平状的灵敏区域设计增大探测器光采集效率,力求提升对于低质量暗物质的探测灵敏度。本论文第五章将介绍由作者开发的名为Panda X Raw Pulse Analyser(PRP)的数据分析系统,以及利用Panda X第一批数据对于低质量暗物质的分析研究。该结果排除了先前其他暗物质探测实验给出的低质量暗物质可能的参数区域[3 6]。
[Abstract]:Numerous astronomical observations and large-scale structural simulations have shown evidence of the existence of dark matter in the universe. In the last 30 years, particles known as WIMP (weakly interacting heavy particles) have been able to match the density of dark matter in the present universe. In the field of direct detection of dark matter, the direct detection of dark matter has been paid more and more attention. LXe-TPC, a two-phase time projection chamber using liquid xenon as a detecting medium, is one of the most popular detection techniques at present. Its main advantage lies in its ability to distinguish and exclude gamma background. The high background exclusion efficiency of the two phase liquid xenon time projection chamber is derived from the electron recoil produced by the gamma background in liquid xenon and the potential nuclear recoil ionization and scintillation signals produced by dark matter. Low energy signal response model in liquid xenon has not achieved reliable accuracy. Among them, the photon electron production rate of recoil electrons in the low energy region (several ke V) need to be improved. In the third chapter of this paper, we will introduce the development and construction of a small two-phase xenon time projection chamber, including vacuum refrigeration, gas-liquid cycle, and so on. The introduction of data acquisition and data analysis system. The detector obtained high energy resolution in trial operation. It is suitable for studying low energy electron and nuclear recoil signals of liquid xenon. In Chapter 4th, the process of detecting low energy recoil signals by using this small two-phase xenon time projection chamber is described in detail. And the signal model I constructed from the obtained data. The signal model updates the lack of understanding of low energy electron recoil and recoil resolution in liquid xenon in existing models. The electronic recoil signal produced by dark matter [1t2] plays a reference role. It also provides the direction for the next generation of liquid xenon detector optimization. In Chapter 5th, this paper will introduce the number of direct detection experiments of Panda X dark matter in detail. According to analysis. Panda X is the first direct dark matter detection experiment in China using two phase liquid xenon time projection chamber technology. It is located in the CJPL(6900 multi-meter equivalent water depth of Sichuan Jinping Underground Laboratory, which has the world's lowest cosmic ray background at present. Panda X first stage detector uses a flat sensitive region design to increase the photoacquisition efficiency of the detector. In chapter 5th, a data analysis system called Panda X Raw Pulse Analyser/ PRP, developed by the author, is introduced. And the analysis of low mass dark matter using the first batch of Panda X data. This result excludes the possible parameter region of low mass dark matter given by other dark matter detection experiments.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P145.9

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