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

粒子物理的标准模型(SM)总结了我们今天关于物质的组成及其基本相互作用的知识。它的主要成分之一是产生粒子质量的希格斯机制。尽管SM与目前最精确的测量结果一致，但它存在一些缺陷，需要进行新物理学(NP)的扩展。这些都需要新的粒子。寻找NP和探索希格斯机制是大型强子对撞机(LHC)的主要任务。与希格斯机制有关的粒子是在它提出假设近50年后由LHC实验发现的。然而，除了可能的线索外，到目前为止还没有发现新的物理学，这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。后者可能表现为希格斯耦合与剩余的SM粒子的偏差，这将导致非标准的产生和衰减率。希格斯率目前的精确度为NP模型中的解释留下了空间。然而，为了正确地解释利率，并能够根据基础模型得出结论，必须从理论上提供最高精度的预测。然后通过与实验数据的拟合对这些进行了检验。市场上过多的NP模型要求在探索过程中采取系统的方法。在这个研究方案的框架下，我们将以自下而上的方法研究SM Higgs部门的一些最简单的扩展，它们与目前的实验和理论约束相兼容：两个Higgs双重态模型(2HDM)，其最简单的单重场扩展(N2HDM)，SM由实数和复单重子场(RxSM和CxSM)扩展(RxSM和CxSM)，以及次最小超对称模型(NMSSM)。这些模型的希格斯扇区包含不止一个希格斯玻色子，可以在最近发射的大型强子对撞机运行2中获得，并且在实验分析中已经部分考虑到了这一点。我们将计算这些模型的希格斯衰变的电弱修正，这与不能从SM取代的QCD修正相反。修正的预期大小对于正确解释LHC Run 2的数据是相关的，对于确定Higgs性质是必不可少的，因此对于确定LHC高光度阶段和未来的线性对撞机的基本模型是必不可少的。各种模型的预测达到的精度以及相同方法的应用将使它们能够与数据进行一致的比较。我们将考虑所有相关的实验和理论限制，这些现象学分析的目的是确定发现希格斯粒子的可观测数据和特征，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.