Automation of electroweak NLO corrections for physics beyond the Standard Model

随着大型强子对撞机上希格斯粒子的发现，建立了标准模型的粒子含量。另一方面，到目前为止，还没有出现令人信服的证据来证明SM以外的物理学。除了直接在大型强子对撞机上进行搜索外，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，这需要准确的预测，包括对强相互作用和电弱相互作用的高阶微扰修正。由于许多不同的流程和各种理论都需要这些工具，因此自动化工具是非常理想的。这个项目的中心目标是开发一个工具，用于计算一般相对论量子场论中的NLO修正，例如标准模型或其扩展。输入应该由一套费曼规则或相当于相应的拉格朗日形式的基本理论和给定散射或衰变过程的外部粒子组成。输出应由相应的前级(树级)和次级级(单环)幅度组成，可直接用于蒙特卡罗程序中的物理预测计算。该工具应自动包括所有相关的贡献，如循环图、计数项和有理项。此外，它还应允许计算前导极近似中的修正，其中只考虑中间共振展开式中的前导项。因此，对于目前还不可能进行完整计算的复杂过程，也可以获得精确的预测。

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.