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Search for New Resonances and Dark Matter Particles with BSM Higgs Boson Productions at the LHC

机译：在大型强子对撞机的BSM Higgs Boson Productions中寻找新的共振和暗物质粒子

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摘要

This dissertation presents searches for dark matter particles and new resonances at the LHC with the ATLAS experiment. The data used in these analyses are produced in proton-proton collisions at a center-of-mass energy of 13 TeV and are collected by the ATLAS experiment, with a total integrated luminosity of 36.1 fb--1.;The experimental signature of new physics in this work involves large missing transverse energy (ETmiss) plus a di-lepton pair from a Z boson decay. In the dark matter search program, it is hypothesized that the Higgs boson may couple to invisible particles who serve as dark matter candidates. The Higgs boson is produced in association with a Z boson, which is used as a 'tag' particle through its charged lepton (ee or mumu) decays. The dark matter signature is large ETmiss since the dark matter particles, just like the neutrinos, escape from the detector (invisible). The challenge of searching for dark matter is to understand sources of ETmiss produced in proton-proton collisions and design an efficient event selection criterion to separate the signal from the backgrounds. Selected data is compared with the expected background and the dark matter signal, assuming the Standard Model (SM) ZH production cross section. Data is found to be consistent with the background expectation. An upper limit on the branching fraction of the Higgs boson decaying to invisible particles of 67% is set at 95% confidence level (CL). The corresponding limits on the production cross-section (sigma) of beyond the SM Zh process with the invisible Higgs boson decays are also presented in a mass range of 110 to 400 GeV.;The two-Higgs-doublet model and the electroweak singlet model are motivated theoretical models, which predict additional Higgs bosons near the TeV scale that may decay to pairs of Z bosons. The search for these non-SM Higgs bosons are also conducted with di-lepton plus E Tmiss final states, but by considering the decay mode ZZ → ℓ+ℓ+ℓ -- (ℓ = e, or mu). The transverse mass spectrum of the ℓ+ℓ-- + ETmiss system is used as the discriminant to search for bumps created by new resonances. Comparing data with the expected signal and background, no evidence is found for new resonance production in the mass range between 300 GeV to 1500 GeV. Therefore, the limits on new resonance production cross-section times a branching ratio are set. This result is also interpreted as a search for a spin-2 Kaluza-Klein graviton excitation, G*KK , in the context of the bulk Randall-Sundrum model via G*KK → ZZ* → ℓ +ℓ-- process. An upper limit on sigma x BR(G*KK → ZZ*) is set as a function of the KK graviton mass between 600 GeV and 2 TeV.
机译：本文利用ATLAS实验提出了在大型强子对撞机中寻找暗物质颗粒和新的共振的方法。这些分析中使用的数据是在质子-质子碰撞中以13 TeV的质心能量产生的，并通过ATLAS实验收集，其总综合光度为36.1 fb--1。这项工作中的物理学涉及大量的横向缺失能量（ETmiss）以及Z玻色子衰变中的双轻子对。在暗物质搜索程序中，假设希格斯玻色子可能与充当暗物质候选物的不可见粒子耦合。希格斯玻色子与Z玻色子结合产生，Z玻色子通过其带电的轻子（ee或mumu）衰变用作“标签”粒子。暗物质特征是大ETmiss，因为像中微子一样，暗物质粒子也从探测器中逸出（不可见）。寻找暗物质的挑战是了解质子-质子碰撞产生的ETmiss的来源，并设计有效的事件选择标准以将信号与背景分离。假定标准模型（SM）ZH的生产横截面，将所选数据与预期背景和暗物质信号进行比较。发现数据与背景预期一致。希格斯玻色子衰变成不可见粒子的支化分数的上限上限为95％置信水平（CL）。在不可见的希格斯玻色子衰变的情况下，SM Zh过程之外的生产截面（sigma）的相应限制也出现在110至400 GeV的质量范围内;两希格斯二重态模型和电弱单重态模型是有动机的理论模型，可预测TeV尺度附近的其他希格斯玻色子，这些希格斯玻色子可能会衰减为Z玻色子对。对这些非SM希格斯玻色子的搜索也使用di-轻子加E Tmiss的最终状态进行，但要考虑到衰减模式ZZ→＆ell; +＆ell; +＆ell; -（＆ell; = e或mu）。 ＆ell; +＆ell;-+ ETmiss系统的横向质谱用作判别，以搜索由新共振产生的碰撞。将数据与预期信号和背景进行比较，未发现在300 GeV至1500 GeV的质量范围内产生新共振的证据。因此，设定了新的共振产生截面乘以分支比的极限。该结果也被解释为在体Randall-Sundrum模型的上下文中，通过G * KK→ZZ *→＆ell;搜索自旋2的Kaluza-Klein引力子激发G * KK。 +＆ell;-过程。 σx BR（G * KK→ZZ *）的上限根据KK引力子质量在600 GeV和2 TeV之间设置。

著录项

  • 作者

    Guo, Wen.;

  • 作者单位

    University of Michigan.;

  • 授予单位 University of Michigan.;
  • 学科 Condensed matter physics.
  • 学位 Ph.D.
  • 年度 2018
  • 页码 169 p.
  • 总页数 169
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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