Precision calculations for loop-induced Higgs-boson production and decay processes

在过去十年中，粒子物理学最重要的成就之一是在大型强子对撞机（LHC）实验中发现了希格斯玻色子。这种新粒子现在是理论和实验上密集研究的中心对象，以精确确定其性质。 特别是，理解这种希格斯玻色子是否只是标准模型（SM）希格斯玻色子，或者它是否是更普遍理论的一部分是很有趣的。为了回答这个问题，精确的理论预测是必要的，无论是在SM内，以及在SM的扩展。这些精确的理论预测在这个项目中得到了解决。环诱导过程在希格斯物理学中起着特殊的关键作用。由于希格斯玻色子只与大质量粒子耦合，希格斯玻色子的产生和衰变过程涉及初始或最终状态的无质量粒子，如胶子或光子，通过大质量粒子环进行。这些循环诱导的过程是重要的，一方面，因为他们大大有助于发现希格斯玻色子在大型强子对撞机，另一方面，他们是敏感的新物理超越SM。最简单的扩展之一的希格斯部门的SM是一个额外的自旋零规范单线添加到SM fieldcontent。这个模型具有丰富的对撞机现象学，可以在LHC上进行测试。这个模型还可以回答SM中仍然没有答案的问题，例如暗物质的性质问题或宇宙的物质-反物质不对称性的起源问题。 在这个项目中，将分析微扰理论中的电弱校正对回路感应过程的影响。由于回路诱导过程的首阶过程已经处于单回路水平，因此次首阶校正的计算在这里已经涉及具有挑战性的双回路图的计算。

One of the most important achievements of particle physics in the last decade was the discovery of a Higgs boson at the Large Hadron Collider(LHC) experiments. This new particle is now central object of intense investigations, both in theory and experiment, in order to precisely determine its properties. In particular, it is interesting to understand whether this Higgs boson is just the Standard Model(SM) Higgs boson or whether it is part of a more general theory. In order to give answers to this question precise theory predictions are necessary, both within the SM as well as within extensions of the SM. These precise theory predictions are addressed in this project.Loop-induced processes play a special key role in the context of Higgs physics. Since the Higgs boson only couples to massive particles, Higgs-boson production and decay processes which involve massless particles in the initial or final state, like gluons or photons, proceed via a massive particle loop. These loop-induced processes are important on the one hand since they contributed substantially to the discovery of a Higgs-boson at the LHC, on the other hand they are sensitive to new physics beyond the SM.One of the simplest extensions of the Higgs sector of the SM is the one with an extra spin-zero gauge singlet added to the SM fieldcontent. This model has a rich collider phenomenology which can be tested at the LHC. This model can also give answers to still open questions, which remain unanswered within the SM, like for example, the question of the nature of dark matter or the question of the origin of the matter-antimatter asymmetry of the Universe. Within this project the impact of electroweak correction in perturbation theory to loop-induced processes shall be analyzed. Since the leading-order process for loop-induced processes is already at the one-loop level, the computation of next-to-leading order corrections involves here already the computation of challenging two-loop diagrams.