研究重向量玻色子特徵訊號

Abstract

這份研究探討了一種質量約在TeV等級的重玻色子衰變為Z玻色子與希格斯玻色子的衰變模式的發現潛力，這種重玻色子出現在非常多種標準模型延伸的模型之中，因為他們對於歸一化WW散射截面是非常重要的。這份研究的特點在於我們對於這種重玻色子的探測是非直接性的，而是透過觀察具有大的垂直動量的希格斯玻色子來達成。這種方法的優點在於我們如果要求Z玻色子衰變為雙輕子，且希格斯玻色子衰變為雙光子的情況下，標準模型預測的背景會非常小。這份研究對於形狀較寬或是連續變化的質量譜也同樣敏銳。我們使用了MadGraph5作為撞擊事件的模擬器，並同時使用Delphes作為偵測器的模擬器，考慮了簡化的CMS環境下的觀測。我們將重玻色子的發現潛力作為積分亮度的函數，整理為統計標準差與排除極限的形式呈現。 為了設定排除極限，我們使用了CMS和ATLAS皆在使用的重向量玻色子(為了設定排除極限，我們使用了CMS和ATLAS皆在使用的重向量玻色子(Heavy Vector Triplet, HVT)模型，也用了一種特定的非局部量子場論模型，在這個模型中ZH衰變並不侷限於一個點，而是使用一些來自超越標準模型的尺度來延伸其衰變範圍。我們的結果非常新，且是第一次在這份結果裡呈現。雖然這份研究只侷限於ZH衰變，這份研究仍然能夠延伸到WH的輕子型衰變，藉此提高發現潛力。

In this thesis, the discovery potential of a Heavy, TeV-mass Vector boson decaying via the Z-boson$+$Higgs channel is presented. Such exotic heavy bosons appear in many Beyond the Standard Model of Particle Physics extensions, as they are necessary in unitarizing the WW cross section. The novelty in this search is that it is indirect, performed only as a search for an excess of Higgs production with high transverse $P_{T}$ of order TeV. The advantage of this strategy is that if we request leptonic Z decays and the Higgs to decay into photons, then the SM Higgs and the diphoton continuum background yields are very small. The search is also sensitive to broad heavy resonances as well as to a continuum. The study uses MadGraph5 as the event generator and Delphes as a fast simulation of the CMS detector at the LHC. The discovery potential as a function of integrated luminosity in terms of statistical significance and exclusion limits is presented. To set limits we use the HVT generic model used by ATLAS and CMS, as well as a particular non-Local QFT model in which the VH vertex is not point-like by extended in a range defined by the scale of the new BSM physics. Our results are novel and presented for the first time in this work. Although here we focus on ZH production, our analysis can be extended to WH leptonic production so that the sensitivity of the search is further increased.