Precision Calculations in the Higgs Sector - Paving the Way to the New Physics Landscape

粒子物理学的标准模型（SM）总结了我们今天关于物质成分及其基本相互作用的知识。它的主要组成部分之一是产生粒子质量的希格斯机制。尽管与目前最精确的测量相一致，但SM仍存在缺陷，需要新物理学（NP）的扩展。这就产生了新的粒子。寻找NP和探索希格斯机制属于大型强子对撞机（LHC）的主要任务。与希格斯机制相关的粒子是在希格斯机制被提出近50年后由大型强子对撞机实验发现的。然而，到目前为止，除了可能的线索之外，新物理学还没有被发现，需要更多的实验数据来澄清。希格斯玻色子本身已经成为探索NP的工具。后者可以表现为希格斯粒子与剩余SM粒子耦合的偏差，这将导致非标准的产生和衰变速率。希格斯粒子率目前的准确性为NP模型的解释留下了空间。然而，为了正确地解释这些速率，并能够在基础模型上得出结论，必须由理论提供最高精度的预测。然后通过对实验数据的拟合来检验这些结果。市场上大量的NP模型要求对其进行系统的探索。在本研究计划的框架内，我们将以自下而上的方式研究与当前实验和理论约束相兼容的希格斯粒子扇区的一些最简单的扩展：双希格斯双重态模型（2HDM），其最简单的单重态场扩展（N2HDM），由实和复杂单重态场扩展的SM （RxSM和CxSM）和次最小超对称模型（NMSSM）。这些模型的希格斯区包含不止一个希格斯玻色子，可以在最近启动的大型强子对撞机运行2中访问，并且部分已经在实验分析中被考虑在内。我们将计算这些模型的希格斯衰变的电弱修正，与QCD修正相反，它不能从SM中接管。修正的预期大小将与LHC第2次运行的数据的正确解释有关，对于确定希格斯粒子的性质，从而在LHC的高亮度阶段和未来的线性对撞机中确定潜在的模型是必不可少的。对各种模型的预测所达到的精度和对相同方法的应用将使它们能够与数据进行一致的比较。我们将考虑到所有相关的实验和理论限制，可预见的后续现象学分析的目标是识别发现希格斯粒子的可观测值和特征，并区分模型。

The Standard Model (SM) of particle physics summarizes our today's knowledge about the constituents of matter and their fundamental interactions. One of its main ingredients is the Higgs mechanism for the generation of particle masses. Although consistent at present with the most precise measurements, the SM suffers from flaws which call for New Physics (NP) extensions. These entail new particles. The search for NP and the exploration of the Higgs mechanism belong to the main tasks of the Large Hadron Collider (LHC). The particle associated with the Higgs mechanism was discovered by the LHC experiments almost fifty years after its postulation. New Physics, however, has not been discovered so far, apart from possible hints, that need more experimental data for their clarification. The Higgs boson has itself become a tool for the exploration of NP. The latter can show up in deviations of the Higgs couplings to the remaining SM particles, which would lead to non-standard production and decay rates. The present accuracy in the Higgs rates leaves room for interpretations within NP models. In order to properly interpret the rates, however, and to be able to draw conclusions on the underlying model, predictions at the highest precision have to be provided by theory. These are then tested by fits to the experimental data. The plethora of NP models on the market calls for a systematic approach in their exploration. In the framework of this research proposal we will investigate in a bottom-up approach some of the simplest extensions of the SM Higgs sector, that are compatible with the present experimental and theoretical constraints: the two Higgs doublet model (2HDM), its simplest extension by a singlet field (N2HDM), the SM extended by a real and a complex singlet field (RxSM and CxSM) and the next-to-minimal supersymmetric model (NMSSM). The Higgs sectors of these models contain more than one Higgs boson, are accessible at the recently launched LHC Run 2 and are partly already taken into account in the experimental analyses. We will calculate the electroweak corrections to the Higgs decays of these models, which in contrast to the QCD corrections cannot be taken over from the SM. The expected sizes of the corrections will be relevant for the proper interpretation of the data at LHC Run 2 and indispensable for the determination of the Higgs properties and hence for pinning down the underlying model in the high-luminosity phase of the LHC and at future linear colliders. The achieved precision in the predictions for the various models and the application of the same methods will enable their consistent comparison with the data. The goal of the foreseen subsequent phenomenological analyses, in which we will take into account all relevant experimental and theoretical constraints, is the identification of observables and signatures for the discovery of the Higgs particles and the distinction of the models.