Automation of electroweak NLO corrections for physics beyond the Standard Model

随着在大型强子对撞机上发现希格斯粒子，标准模型的粒子含量已经建立。另一方面，迄今为止，除了SM之外，没有令人信服的物理证据出现。除了在大型强子对撞机进行直接搜索外，发现新物理学的一个关键是对标准过程的精确研究。在理论方面，这些需要精确的预测，包括强和电弱相互作用的高阶微扰修正。由于许多不同的过程和各种理论都需要这些工具，因此非常需要自动化工具。这种计算强相互作用修正的工具已经存在，但还没有用于计算电弱相互作用修正的工具。该项目的中心目标是开发一种工具，用于自动计算广义相对论量子场理论（如标准模型或其扩展）中的NLO修正。输入应该包括基础理论，以一组费曼规则或相应的拉格朗日规则的形式，以及给定散射或衰变过程的外部粒子。输出应由相应的首阶（树级）和次阶（单环）振幅组成，可直接用于蒙特卡罗程序中物理预测的计算。该工具应自动包括所有相关的贡献，如循环图、反项和有理项。此外，它还允许计算前导极近似的修正，其中只考虑了中间共振展开中的前导项。因此，对于目前无法进行完整计算的复杂过程，也可以得到精确的预测。

With the discovery of the Higgs particle at the LHC the particle content of the Standard Model has been established. On the other hand, no convincing evidence for physics beyond the SM has emerged so far.Besides direct searches at the LHC, a key for the discovery of new physics are precision investigations ofstandard processes. On the theoretical side these require accurate predictions including higher-order perturbative corrections of the strong and electroweak interaction. As these are needed for many different processes and in various theories, automated tools are highly desirable. Such tools exist for the calculation of corrections of the strong interaction but not yet for the electroweak interaction.The central goal of this project is the development of a tool for the automated calculation of NLO corrections in general relativistic quantum field theories such as the Standard Model or extensions thereof. The input should consist of the underlying theory, in form of a set of Feynman rules or equivalently the corresponding Lagrangian, and the external particles of a given scattering or decay process. The output shall consist of the corresponding leading-order (tree-level) and next-to-leading-order (one-loop) amplitudes, which can be directly used for the calculation of physical predictions in Monte Carlo programs. The tool shall automatically include all relevant contributions, such as loop diagrams, counter terms and rational terms. Moreover it shall allow to calculate corrections in the leading-pole approximation, where only the leading terms in an expansion about intermediate resonances are taken into account. Thus, precise predictions can be obtained also for complicated processes for which complete calculations are presently not feasible.