Dark matter searches and study of electrode design in LUX and LZ
Dark matter searches and study of electrode design in LUX and LZ
复制标题
DOI：
--
复制
发表时间：
2016-10
期刊：
影响因子：
--
通讯作者：
A. Bailey
中科院分区：
文献类型：
--
作者：
A. Bailey
有大量的证据表明，宇宙中超过80%的物质是暗物质-这是非重子的性质，被认为是由一种新的，缓慢移动的，稳定的粒子在粒子物理学标准模型中没有发现。它的存在是从引力对发光物质的影响中推断出来的，这些影响来自几个独立的观测，从银河系到宇宙学尺度。弱相互作用大质量粒子（WIMPs）是主要的候选者，它可以解释所有观察到的效应。LUX和LZ是双相氙时间投影室（TPC），旨在观察氙核的WIMP散射。LUX的有效质量为250千克液态氙，并于2013年至2016年期间在南达科他州的桑福德地下研究设施中获取数据。2013年首次运行的85天的WIMP搜索为自旋无关的WIMP-核子截面设定了世界领先的排除限制。通过重新分析这些数据，以及随后的一次新的运行得到了332个存活日，这为50 GeV的WIMP（90% CL）设定了2.2 × 10−46 cm 2的最小排除极限。此外，迄今为止对与自旋无关的WIMP-中子散射截面的最严格限制来自对2013年数据集的重新分析，对于33 GeV的WIMP，最小排除为9.4 × 10−41 cm 2。LZ是下一代实验，具有7吨重的活动质量，将部署在与LUX相同的位置，预计灵敏度高出100倍。本论文的工作包括分析2013年LUX搜索数据以产生自旋相关结果，使用氚β−源评估探测器响应，并从数据中确定85 Kr背景。利用LUX工程数据，在高电场下对细阴极线的杂散电子发射现象进行了研究，其中电网电压增加到标称工作值以上;这导致了对几十年来影响这些（和其他）TPC探测器的微观击穿机制的新见解。在LUX中获得的电致发光响应的详细理解被应用到LZ电致发光区域的设计;电极几何形状的详细模拟工作被执行以评估几个候选设计的性能。
There is substantial evidence that over 80% of matter in the universe is dark matter – which is non-baryonic in nature and is thought to be composed of a new, slow-moving, stable particle not found in the Standard Model of Particle Physics. Its presence is inferred from gravitational effects on luminous matter from several independent observations, from the galactic to the cosmological scale. Weakly Interacting Massive Particles (WIMPs) are the leading candidate, which can explain all of the observed effects. LUX and LZ are dual-phase xenon time projection chambers (TPC), aiming to observe scattering of WIMPs from xenon nuclei. LUX has an active mass of 250 kg of liquid xenon, and took data at the Sanford Underground Research Facility in Lead, South Dakota, between 2013 and 2016. The first WIMP search run of 85 live days in 2013 set world-leading exclusion limits on the spin-independent WIMP-nucleon cross section. This was improved by a reanalysis of those data, and subsequently by a new run yielding 332 live days, which set a minimum exclusion limit of 2.2 × 10−46 cm2 for a 50 GeV WIMP (90% CL). In addition, the most stringent limit to date on the spindependent WIMP-neutron scattering cross section comes from the reanalysis of the 2013 dataset, with a minimum exclusion of 9.4 × 10−41 cm2 for a 33 GeV WIMP. LZ is a next generation experiment with a 7 tonne active mass to be deployed in the same location as LUX, expected to be 100 times more sensitive. Work presented in this thesis includes analysis of the 2013 LUX search data to produce the spin-dependent results, evaluating the detector response using a tritium β− source, and determining the 85Kr background from data. A study was carried out on spurious electron emission phenomena from thin cathodic wires under high electric fields, using LUX engineering data where the grid voltages were increased above nominal operating values; this led to new insights into the microscopic breakdown mechanisms which have affected these (and other) TPC detectors for decades. The detailed understanding of the electroluminescence response gained in LUX was applied to the design of the LZ electroluminescence region; detailed simulation work of electrode geometry was performed to assess the performance of several candidate designs.