Toward discovering the low-mass dark matter: Constraints on Searches of Low-mass Weakly Interacting Massive Particle (WIMP) with Earth Attenuation Effect incorporated && Exploring the physics of germanium internal amplification for low-energy detection

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题名:	Toward discovering the low-mass dark matter: Constraints on Searches of Low-mass Weakly Interacting Massive Particle (WIMP) with Earth Attenuation Effect incorporated && Exploring the physics of germanium internal amplification for low-energy detection
作者:	葉智翔;Yeh, Chih-Hsiang
贡献者:	物理學系
关键词:	低質量暗物質;地球衰減效應;米格達爾效應;軔致輻射效應;鍺電離檢測器;信號放大;low-mass WIMP dark matter;earth attenuation effects;Migdal effect;bremsstrahlung effect;germanium ionization detectors;signal amplification
日期:	2021-07-22
上传时间:	2021-12-07 12:04:45 (UTC+8)
出版者:	國立中央大學
摘要:	本論文即將介紹兩個不同方向的探測低質量暗物質的研究計畫。第一個計畫是研究有關於地球衰減效應對於實驗站觀測暗物質的影響。此計畫使用了來自TEXONO以及CDEX實驗的數據，這兩個實驗站分別位於地表上存放核反應爐的建築物裡，以及地底下。而此實驗考慮了兩個近期新預測的交互作用效應，分別為米格達爾(Migdal)效應以及軔致輻射(Bremsstrahlung)效應，這樣的考慮允許實驗站可以量測到最低的暗物質質量為50MeV。而我們也發現對於不同的暗物質質量，由於兩個實驗分別被大氣層以及2.5公里的岩石覆蓋層，兩個實驗分別在範圍為${\rm 10^{-26}}$至${\rm 10^{-28}}$${\rm cm^{2}}$以及${\rm 10^{-28}}$至${\rm 10^{-30}}$${\rm cm^{2}}$的產生截面積之間達到了實驗能探測的交互作用強度上限。第二個計畫主要是文獻研究，目的在於理解鍺電離檢測器中信號放大的機制以及實驗的挑戰。這種新穎的探測器，可以將檢測器閾值降低一個數量級到10 eV 的範圍，從而打開搜索更低質量暗物質的新窗口。 ;Two research projects in separate directions related to the goals of discovering low-mass WIMP dark matter are presented in this thesis. The first project is on the studies of earth attenuation effects to WIMPs and how this may affect the experimental constraints. Analysis methods are applied to data recorded by the TEXONO and CDEX experiments, located in a reactor building on earth surface and at an underground site, respectively. Constraints are derived with the newly-identified Migdal and bremsstrahlung effects taken into account which allows the probe of WIMP mass as low as 50MeV. It is found that WIMP-nucleon spin-independent cross-sections above the ones from ${\rm 10^{-26}}$ to ${\rm 10^{-28}}$${\rm cm^{2}}$ and the ones from ${\rm 10^{-28}}$ to ${\rm 10^{-30}}$${\rm cm^{2}}$ for different WIMP masses cannot be experimentally probed since the WIMPs are totally suppressed by the Earth′s atmosphere and by 2.5 km of rock overburden, respectively. The second project is on literature research which targets at the understanding of physical mechanisms and experimental challenges of achieving signal amplification in germanium ionization detectors at 4K and 77K. This novel detector concept, when successfully realized, allows reduction of detector threshold by an order of magnitude to the range of 10 eV, thereby opening new windows of light WIMP searches.
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