在緊湊渺子線圈實驗中尋找磁單極

Abstract

本論文分為兩部分：第一到八章為在CMS實驗中尋找磁單極，以及第九章之對地震與異常氡氣釋放的相關性研究。

第一部分：自從保羅狄拉克在一九三一年提出電荷量子化條件之後，尋找磁單極成為物理學家的重要課題之一。本論文描述在緊湊渺子線圈實驗內尋找磁單極，以證明狄拉克電荷量子化條件的理論。本研究使用了僅有磁單極信號的蒙地卡羅樣本模擬磁單極在緊湊渺子線圈實驗內的產生，並用從2016年至2018年間所收集之對撞質心能量為13兆電子伏特的質子-質子對撞事件中，尋找磁單極的訊號。本論文使用的模型為經德雷爾-顏過程產生之自旋1/2的磁單極對，並基於磁單極於模擬時出現的特徵做為分析策略。由於磁單極最低的磁荷|g_{D}|=1相當於基本電荷量e的68.5倍，導致其與物質的交互作用非常強烈，因此磁單極被視為一種高度電離粒子。其中一個顯著的特徵即磁單極傾向飽和軌跡追蹤系統裡的矽條帶。另一特徵為磁單極在電磁量能器的少數幾個閃爍晶體中迅速製造出電磁射叢，導致其有如尖端一般的拓撲性質，最後因堆積大部分的能量而停留在電磁量能器中。本研究也提高了信號的效率並提供未來可投入使用的觸發器研究。最後，由於本實驗的信號靈敏度低，因此在95%的信心水準之下，可預期磁單極的質量大約為2320十億電子伏特。

第二部分：為防範大型地震對人類造成的危害，預測地震一直是地震學家關注的課題之一，其一理論認為放射性氣體-氡氣從地底異常大量之釋放可被視為大地震之前兆。本論文利用台大高能團隊開發出之晶體偵測器，放置在地震頻發的花蓮氣象站，至今已搜集兩年含有氡氣訊號之 𝛾-ray光譜，並且從中央氣象局蒐集地震事件及地震波形，以研究大型地震與異常氡氣釋放事件的相關性。然而本論文蒐集之放射性光譜經各種校正嘗試及研究後，證實其受到當地氣溫影響而有失真現象，因此未能提供精準的相關性研究。

This thesis consists of two parts, one is the search for magnetic monopole in CMS experiment from chapter 1 to 8, the other is sensing the earthquake from anomalous radon emission in chapter 9.

For the first part, since the charge quantization condition was proposed by Paul Dirac in 1931, the search for magnetic monopole comes to a vital topic for physicists. This thesis describes the search for magnetic monopole in the CMS Experiment, in order to prove the idea of the charge quantization condition. The study utilizes the signal MC sample to simulate the monopole production in the CMS experiment and search the signal events collected from the proton-proton collisions at a center-of-mass energy of 13 TeV from 2016 to 2018. The model used in this thesis is the spin-1/2 magnetic monopole pair from the Drell-Yan process. The analysis strategy is based on the monopole's signature in the simulation. Because the monopole is seen as a highly ionized particle where the lowest magnetic charge |g_{D}|=1 corresponds to 68.5 times the elementary electric charge e, this would lead to a strong interaction with material strongly. Therefore, one significant characteristic is that monopoles tend to saturate the silicon strips in the Tracker. On the other hand, monopoles produce EM shower rapidly in a few ECAL crystals, causing a spike-like topological property, depositing most energy, and stopping in the ECAL eventually. This study also improves signal efficiency and provides the trigger study for future implementation. In the end, because of the low sensitivity to the signal, therefore, the limit on the mass is set to be 2320 GeV at 95% confidence level.

For the second part, to prevent human beings from disasters - big earthquakes, predicting earthquakes has been one significant issue for seismologists. One theory speculates that the anomalous radioactive radon emitting from the underground can be considered a precursor of big earthquakes. The NTUHEP developed a crystal detector, deployed in the Hualien weather station where earthquakes frequently happen, to collect the 𝛾-ray spectrum that includes radon signal. Plus, the earthquake events and waveform data are also collected, in order to analyze the correlation between anomalous radon emission and earthquakes. However, after the calibration test and study, data quality is proved to be distorted, which is affected by the local temperature. Therefore, an accurate correlation study cannot be provided in the thesis.