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

次次次前导阶的减法方案及其在顶夸克和喷流物理中的应用

• 批准号: 266457746
• 负责人: Professor Dr. Michal Czakon
• 金额: --
• 依托单位: Cavendish Laboratory
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/266457746?language=en
• 关键词: Subtraction; schemes; next; leading; order

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.

基本粒子物理学的进展与大型强子对撞机的成功密切相关。这个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，希格斯玻色子是标准模型（SM）质量产生机制预测的标量共振。为了证实探测的说法，进行分析的实验学家使用了非常先进的理论工具：强耦合常数下的信号截面的次-次-领先阶（NNLO）微扰展开和次-领先阶结果，包括背景的多粒子发射，称为部分子簇射。目前，还没有进一步共振的证据，很明显，有很高的要求，一个精确的理论理解可能的SM前景和背景过程，以及评估的准确性的预测。所需的努力可能对进一步的发现至关重要。 该项目的目的是为LHC未来成功所需的理论研究做出贡献。这个概念是分析两个过程，顶夸克对生产和双喷生产，在次到次到领先的微扰QCD和开发的一般工具，各自的微分截面的高精度评估。这两个过程之间的联系是建立在需要进行蒙特卡罗模拟的贡献，真实的辐射与多达两个排放的无质量部分子。这可以在很大的一般性，我们计划开发的方法和实现它们的软件，将公开提供和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，它允许确定质子内部的顶夸克质量、强耦合和胶子分布函数。此外，它构成了新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的情况下所推测的那样。另一方面，精确地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。