Subtraction schemes at next-to-next-to-leading order with applications to top-quark and jet physics

基本粒子物理的进展与大型强子对撞机的成功密切相关。这项实验已经提供了一个基本的发现：一种符合希格斯玻色子轮廓的新粒子，标准模型(SM)的质量生成机制预测了一种标量共振。为了证实探测的说法，执行分析的实验者使用了非常先进的理论工具：强耦合常数中信号截面的次要次要顺序(NNLO)微扰展开，以及包括多粒子发射的背景的次要次要顺序结果，即所谓的部分子簇射。目前，没有进一步共振的证据，显然，对可能的SM前景和背景过程的精确理论理解以及对预测的准确性的评估是非常必要的。所需的努力可能会被证明是进一步发现的关键。拟议项目的目的是为大型强子对撞机未来的成功所需的理论研究做出贡献。其概念是分析两个过程，顶夸克对产生和双喷流产生，在微扰QCD的次要数量级上，并开发通用工具来高精度地评估各自的不同截面。这两个过程之间的联系是通过需要对实际辐射的贡献进行蒙特卡洛模拟来建立的，其中最多发射两个无质量部分子。这可以在很一般的情况下完成，我们计划开发方法并在软件中实现它们，这些软件将公开提供并适用于任意对撞机过程。在唯象方面，所选择的顶夸克对产生过程的相关性在于它允许确定顶夸克质量、强耦合和质子内部的胶子分布函数。此外，它构成了新的物理搜索的重要背景，并可能隐藏新的物理效应，正如在Tevatron测量的众所周知的不对称异常所推测的那样。另一方面，精确了解双喷流产生的微分截面对于确定胶子分布函数是至关重要的。

Progress in Elementary Particle Physics is tightly related to the success of the Large Hadron Collider. This experiment has already provided one fundamental discovery: a new particle that fits the profile of the Higgs boson, a scalar resonance predicted by the mass generation mechanism of the Standard Model (SM). In order to substantiate the claim for detection, experimentalists performing the analysis have used tremendously advanced theoretical tools: next-to-next-to-leading order (NNLO) perturbative expansions of the signal cross sections in the strong coupling constant and next-to-leading order results including multiple particle emission, known as parton showering, for backgrounds. At present, there is no evidence for further resonances, and it is clear that there is high demand for a precise theoretical understanding of possible SM foreground and background processes together with the assessment of the accuracy of the predictions. The required effort might prove crucial in making further discoveries. It is the purpose of the proposed project to contribute to the theoretical studies needed for the future success of the LHC. The concept is to analyse two processes, top-quark pair production and di-jet production, at the next-to-next-to-leading order of perturbative QCD and develop general tools for a high precision evaluation of the respective differential cross sections. The link between the two processes is established by the need to perform Monte Carlo simulations of the contribution of real radiation with up to two emissions of massless partons. This can be done in great generality, and we plan to develop methods and implement them in software that will be publicly available and applicable to arbitrary collider processes. On the phenomenological side, the relevance of the selected process of top-quark pair production lies in the fact that it allows for the determination of the top-quark mass, the strong coupling, and the gluon distribution function inside the proton. Furthermore, it constitutes an important background for new physics searches and may hide new physics effects, as speculated in the case of the well-known asymmetry anomaly measured at the Tevatron. On the other hand, a precise knowledge of the differential cross section for di-jet production is crucial in the determination of the gluon distribution function.