在對撞能量十三兆電子伏特的緊湊渺子螺線圈實驗中透過希格斯玻色子的雙光子衰變態去測量向量玻色子及希格斯玻色子共伴產生之截面

Measurements of the associated VH production cross section in the H to γγ channel at sqrt(s) = 13 TeV in the CMS experiment

李侑穎(You-Ying Li)

指導教授 ： 裴思達

國立臺灣大學/理學院/物理學研究所/博士(2021年)

https://doi.org/10.6342/NTU202102141

摘要

此論文主要描寫藉由希格斯玻色子的雙光子衰變態中測量向量玻色子及希格斯玻色子共絆產生的截面積研究以及相關的背景知識，此測量使用從 2016 至 2018 年，藉由緊湊緲子螺線圈收集的質心能量 13 兆電子伏特的質子對撞事件，其總亮度達到 137 逆飛靶。分析策略採用”簡化型模板截面積“架構去提升向量玻色子及希格斯玻色子共絆產生的靈敏度，並提供此共絆產生的運動學結構之測量。這個架構根據不同的產生機制以及運動學去分割向量玻色子及希格斯玻色子共絆產生的截面積到不同的區域，同時，對撞事件也被區分成不同的類別去豐富這些類別所瞄準的區域，此外，每個類別也採用促進式決策樹去優化此共絆產生的靈敏度。經過對所有類別裡的雙光子不變質量的分佈進行最尖端的同步擬合後，測量到向量玻色子及希格斯玻色子共絆產生的訊號強度為 1.34^{+0.36}_{-0.33} ，一致的顯著度相對於背景達到 4.7 個標準差。另外，向量玻色子及希格斯玻色子共絆產生的截面積在不同的產生機制以及運動學也被測量，全部的結果符合標準模型的預測。

關鍵字

大型強子對撞機 ； 緊湊緲子螺線圈 ； 標準模型 ； 向量玻色子及希格斯玻色子 ； 雙光子衰變 ； 簡化型模板截面積

並列摘要

Measurements of the associated VH production cross section with the Higgs boson decaying to a pair of photons are revealed. The measurements use events collected from the CMS experiment with proton-proton collisions at a center-of-mass energy of 13 TeV from 2016 to 2018, giving an integrated luminosity of 137 fb^{-1} . The analysis strategy uses the simplified template cross section (STXS) framework to improve the sensitivity of the associated VH production and provide a measurement of its kinematic structure. The framework splits the cross section of the associated VH production into several bins with different productions and kinematics. At the same time, the events are divided into different analysis categories to enrich their targeting bins. Boosted Decision Tree technique is also applied in each analysis category to optimize the sensitivity. Eventually, through the state of the art simultaneous fit to the diphoton invariant mass distribution in all the analysis categories, the inclusive signal strength modifier of the associated VH production is measured to be 1.34^{+0.36}_{-0.33} with an observed significance of 4.7 sigma. The cross sections of the associated VH production in different productions and kinematic regions are also measured. The results are totally in agreement with the Standard Model prediction.

並列關鍵字

LHC ； CMS ； Standard Model ； VH ； diphoton ； STXS

參考文獻

CMS Collaboration, “A New Boson with a Mass of 125 GeV Observed with the CMS Experiment at the Large Hadron Collider”, Science 338 (2012) 1569–1575.

ATLAS Collaboration, “A particle consistent with the Higgs Boson observed with the ATLAS Detector at the Large Hadron Collider”, Science 338 (2012) 1576–1582.

Particle Data Group, “Review of Particle Physics”, PTEP 2020.8 (2020) 083C01.

CMS Collaboration, “Observation of the Diphoton Decay of the Higgs Boson and Measurement of Its Properties”, Eur. Phys. J. C 74.10 (2014) 3076.

CMS Collaboration, “Measurements of Higgs boson properties in the diphoton decay