於對撞能量十三兆電子伏特的緊湊緲子線圈實驗藉由希格斯玻色子的雙光子衰變通道搜尋頂夸克味變中性流及似向量夸克和參與 CMS 高粒度量能器第二期升級計畫

Abstract

本論文包含三個主題。第一個主題為頂夸克和希格斯玻色子之間的味道改變中性流相互作用(FCNH)，其中希格斯玻色子衰變為兩個光子。第二個主題則是尋找由電弱相互作用產生並衰變為頂夸克和希格斯玻色子的類向量夸克(VLQ) T'，同樣是在希格斯玻色子的雙光子衰變通道進行研究。第三個主題涉及高粒度量能 器(HGCAL)二期升級項目的各種研究。

前兩項研究基於2016年至2018年間在大型強子對撞機(LHC)的緊湊緲子線圈(CMS)探測器收集的質子對撞數據，對撞質心能量為十三兆電子伏特，總亮度為 138 fb−1。觀測結果未發現明顯超出背景預測的事件訊號。在 FCNH 研究中，在 95% 信心水準下，論文給出當時最靈敏的 t → qH 分支比的上限;在 VLQ 研究中，排除了耦合常數為 0.25 時，質量高達 960 GeV 的類向量夸克。 在關於 HGCAL 項目的第三部分，研究成果包括為 HGCAL 縱向簇射剖面中的一個獨特特徵找到了可行的解釋、量化了替代觸發方案對能量解析度的影響、以及個人參與原始數據處理項目。在該項目中，筆者參與了校準算法在GPU核心中開發，處理一百萬筆數位化信號 (digitized hits) 時速度提高了10倍。此外，筆者更於 CMS 數據品質監測服務中，實現了一種新型的監視元素，使得在2023年 HGCAL 光束測試實驗期間，能夠實時監控多邊形矽晶圓圖。這一里程碑標誌著 HGCAL 系統數據品質監測服務的開始。

The dissertation consists of three topics. The first topic is concerned with a search for the flavor-changing neutral current interaction between a top quark and a Higgs boson (FCNH), with the Higgs boson decaying to two photons, H → γγ. The second topic is engaged in a search for the vector-like quark (VLQ) T’ produced from electroweak interactions and decaying to a top quark and a Higgs boson in the two-photon channel. The third topic involves various studies in the phase-2 upgrade project for the high-granularity calorimeter (HGCAL).

The first two studies are based on the data of the proton-proton collision at √s = 13 TeV collected with the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) between 2016 and 2018, corresponding to an integrated luminosity of 138fb−1. No significant excess above the background prediction is observed. The dissertation presents competing upper limits on the t → qH branching fractions in the FCNH study and excludes the electroweak production of T’ with masses up to 960 GeV at a 95% confidence level with coupling κT = 0.25 in the VLQ study.

In the third part concerning the HGCAL project, the research results include discovering a feasible explanation for a distinctive feature in the longitudinal shower profile in HGCAL, quantifying the energy resolution degradation with an alternative trigger scheme, and personal involvement in the raw data handling project. In the project, calibration algorithms were developed in GPU kernels, resulting in a 10x speed-up when processing 1M hits. Furthermore, a new type of monitor element was implemented in the CMS DQM service, allowing real-time polygonal silicon wafer map monitoring during the 2023 HGCAL beam test event. This milestone signifies the start of the DQM for the HGCAL system.