緊湊渺子線圈第二期升級研究：濤輕子在高粒度量能器中的重構與辨識及使用矽光電倍增元件量測LYSO之時間解析度

Abstract

此論文呈現了與為了高亮度大型強子對撞機而進行的緊湊渺子線圈第二期升級相關的兩個研究。在第一個研究，我們討論了將在第二期升級時取代現有量能器的高粒度量能器的表現。它不僅能提供更好的空間與時間解析度，更是能利用它層狀的構造進行三維的粒子重構。我們呈現了使用高粒度量能器進行濤輕子重構與識別的性能，顯示它在200個對撞事件的積累情況下具有良好的表現。然而為了充分發揮高粒度量能器的潛力，能量校正等數個問題仍需解決。在第二個研究，我們探討了LYSO晶體放光的時間解析度。同樣在緊湊渺子線圈第二期升級時，LYSO晶體將會用於將最小電離粒子時間探測器以提供精確的時間測量。而為了達到如此精確的時間解析度，我們使用了處於蓋格模式下的矽光電倍增元件進行探測。我們呈現了在不同參數設定下所量測到的時間解析度，包括矽光電倍增元件的工作電壓、訊號閾值以及LYSO晶體的大小與摻雜成分。透過我們的設置可以獲得80皮秒的單個LYSO晶體的時間分辨率。

Two aspects of studies related to the phase-II upgrade of CMS for the HL-LHC are presented. In the first topic, we discuss the performance of the High Granularity Calorimeter, HGCAL, which will replace pre-shower, ECAL, and HCAL in the end-cap region of CMS. Not only having better resolutions in x, y, and timing measurement, but it also has additional z information and thus can perform a 3D reconstruction. The performance of tau lepton reconstruction and identification with HGCAL are presented and they have good performances under the 200 pile-up situation. Several issues such as energy correction still need to be addressed to achieve the full potential of HGCAL. In the second topic, we study the time resolution of light generated in LYSO crystals. LYSO crystals will be utilized in the MIP Timing detector, MTD, which will also be implemented in the CMS phase-II upgrade for precise time measurement. To reach this time requirement, we make use of Silicon Photon-Multipliers(SiPM), which is a Geiger mode silicon detector. We present the time resolution with several setup parameters, including operation voltage and threshold for SiPMs and different sizes and dopings of LYSO crystals. The time resolution of a single LYSO crystal of 80 picoseconds is obtained with our setup.