Studies of the properties of the Higgs Boson

粒子物理的标准模型是一个非常成功的理论，它描述了物质的基本成分及其相互作用。在过去的40年里，它被证明在预测我们的实验观察到的结果方面非常准确，包括2012年由ATLAS和CMS的合作发现的希格斯玻色子的存在。尽管流行的粒子物理理论标准模型具有很强的预测能力，但仍有一些现象无法用该理论来描述，这暗示着在标准模型之外必然存在新的物理，暗物质和暗能量就是两个例子。本文将报告对希格斯玻色子性质进行精确测量的结果，以寻找超出标准模型的新物理。两个例子是希格斯粒子的质量和宽度，它们为理论提供了强有力的测试，而它们的测量是本论文的主要目标。考虑到ATLAS将在未来三年收集的大量数据集，H-&GT；ZZ-&GT；4L通道将提供对希格斯质量的最精确测量，特别是对Muon末态的测量。这一测量与W玻色子和顶夸克质量等其他标准模型参数的测量结果一起，可以直接用于检验标准模型的一致性。测量希格斯玻色子宽度提供了非常有趣的信息，因为它对希格斯玻色子对不可见粒子的衰变非常敏感。在大型强子对撞机上，这种测量是不可能的，因为预期的宽度约为4 MeV，几乎比实验分辨率小了三个数量级。然而，如果我们假设希格斯玻色子的耦合不依赖于产生它的能量，那么对希格斯玻色子宽度的限制可以从对H-&gt；zz-&gt；4l(2l2v)终态中“壳上”和“壳外”信号强度的测量中提取出来。(2l2v)终态对新的质量更高的希格斯粒子也很敏感，这些粒子是在扩展标准模型的理论中预测的。如果有足够的时间，这些新的希格斯粒子也将被搜索，并且搜索继续具有实验和理论上的兴趣。除了分析质子-质子碰撞数据，ATLAS的学生必须对实验做出技术贡献，才有资格成为作者。这对学生的教育很重要，对实验来说也是必要的，这样才能保持操作和良好的监控。Atlas正在着手对探测器进行雄心勃勃的升级，Ricardo将通过高统计研究参与其中，以了解用于硅相机升级的130 nm读出电子ASIC对电离辐射的响应。

The Standard Model of particle physics is a very successful theory, describing the fundamental constituents of matter and their interactions. In the past 40 years it has proven to be extremely accurate in predicting the results observed by our experiments, including the presence of the Higgs boson, discovered in 2012 by the ATLAS and CMS collaborations. Despite the great predictive power of the Standard Model, the prevailing theory of particle physics, there are phenomena which are not described by the theory, hinting that new physics must exist beyond the Standard Model, two examples are dark matter and dark energy.The thesis will report the results of performing precision measurements of the properties of the Higgs boson, in order to look for new physics beyond the Standard Model. Two examples are the mass and the width of the Higgs that provide a powerful test of the theory and their measurement are the principal goals of the thesis. Given the large dataset that ATLAS will collect in the next three years, the H->ZZ->4l channel will provide the most precise measurement of the Higgs mass, especially for the muon final states. This measurement, together with those of other Standard Model parameters such as the W boson and top quark masses, can be used to directly test the consistency of the Standard Model. Measuring the Higgs boson width provides extremely interesting information as it is sensitive to the decays of the Higgs boson to invisible particles. At the LHC this measurement is not directly possible, given that the expected width is about 4 MeV, almost three orders of magnitude smaller than the experimental resolution. A constraint on the width of the Higgs boson can, however, be extracted from the measurement of the "on-shell" and "off-shell" signal strengths in the H->ZZ->4l (2l2v) final states, if we assume that the couplings of the Higgs boson do not depend on the energy at which it is produced. The (2l2v) final state is also sensitive to new Higgs particles at higher mass that are predicted in theories that extend the Standard Model. A search for these new Higgs particles will also be made if sufficient time exists and the searches continue to be of interest experimentally and theoretically.In addition to the analysis of the proton-proton collision data, an ATLAS student must make a technical contribution to the experiment in order to be qualified for authorship. This is important for the education of the student and necessary for the experiment in order for it to remain operational and well-monitored. ATLAS is embarking on an ambitious upgrade of the detector and Ricardo will be involved in this through high statistics studies to understand the response of the 130 nm readout electronic ASICs for the silicon camera upgrade to ionizing radiation.