# Topical Collaboration for QCD at Energy Frontier

## Collaboration Goal

On August 15–17, 2020, a strategic meeting was held at QingDao to discuss the roadmap for the development of accelerator based particle physics in China in the period 2021–2035. A detailed stragetic report is expected to be finished by November, 2021 for several different research areas, including perturbative QCD at high energy. This collaboration is formed aiming at joining the theoretical efforts of perturbative QCD in China to accomplish the goal.

# List of subtopic

## 已有的研究方向和有意向撰写的同事：

• 强耦合常数的精细测量
• 高俊（上海交通大学），朱华星（浙江大学）
• 因子化定理的检验及其幂次修正
• 王健（山东大学），朱华星（浙江大学）
• 结构函数的全局拟合
• 高俊（上海交通大学）
• 散射振幅的理论和技术发展
• 高阶QCD和电弱辐射修正
• QCD喷注及其亚结构的研究
• 朱华星（浙江大学）
• Higgs和顶夸克的QCD物理
• B物理中的高阶QCD修正
• 李新强（华中师范大学）
• 高能散射事例模拟和产生子

# Collaboration Members

Anyone who is willing to contribute to the report is welcome to join the collaboration. Please send an email to Hua Xing Zhu, specifying which subtopic you want to contribute to.

• Jun Gao, Shanghai Jiao Tong University
• Tie-Jiun Hou, Northeastern University
• Xin-Qiang Li, HuaZhong Normal University
• Zhao Li, Institute of High Energy Physics
• Jian Wang, Shandong University
• Li Lin Yang, Zhejiang University
• Hua Xing Zhu, Zhejiang University, contact person

## 2020

##### September 18, Friday, 1pm – 3pm.
• Constructing Canonical Feynman Integrals with Intersection Theory, Jiaqi Chen, Peking University
Abstract (click to expand) Canonical Feynman integrals are of great interest in the study of scattering amplitudes at the multi-loop level. In this talk, I will present our recent work on constructing canonical Feynman integrals with intersection theory. We construct $d\log$-form integrals which do not obviously correspond to Feynman integrals. We then treat them in a concrete representation of loop integrals, and project them to a set of master integrals using intersection theory. This exploits the geometric picture of hypergeometric integrals and the theory of twisted cohomology. Our method provides a constructive way to build canonical master integrals whose differential equations can be solved easily. We use our method to investigate both the maximally cut integrals and the uncut ones at one and two loops, and demonstrate its applicability in problems with multiple scales.
• Large logarithms at subleading power, Jian Wang, Shandong University
Abstract (click to expand) The large logarithms in the amplitudes or cross-sections are important for making precision predictions beyond fixed-order orders. They have a close relation with the infra-red structure of the amplitudes/cross-sections, and can usually be resummed by the anomalous dimensions of relevant operators. The leading power series of these logarithms has been fully understood since the investigation several decades ago. However, the subleading power series is rarely studied. Recently, much efforts have been devoted to this topic and a lot of new features appear, such as the end-point singularities, new hypergeometric functions and numbers in the result, large logarithms in the anomalous dimensions.
##### August 21, Friday, 1pm – 3pm.
• A Forest-based Infrared Subtraction for Wide-angle Scattering, Yao Ma, Stony Brook University
Abstract (click to expand) I will develop a BPHZ-like forest formula to subtract the IR singularities systematically in QCD. A related analysis has been carried out by Collins for the back-to-back Sudakov form factors, and is generalized here to any wide-angle kinematics with an arbitrary number of external momenta. After a brief introduction to Minkowskian IR divergences in momentum space, I will first illustrate that the approximations yield much richer IR structures than those of an original amplitude, then construct the forest formula and prove that all the singularities appearing in its subtraction terms cancel pairwise. Finally, with the help of this forest formula, the full amplitude can be reorganized into a factorized expression, proving the all-order hard-soft-collinear factorization.
• Calculation of Multi-loop Feynman Integrals, Long-Bin Chen, Guangzhou University
Abstract (click to expand) Feynman integrals are essential for multi-loop calculations. Understanding the mathematical structure of Feynman integrals will be important to handle the complexity of their calculation and may help us to obtain a better understanding of the perturbative quantum field theory. The study of the mathematical properties of Feynman integrals has attracted increasing attention both by the physics and the mathematics communities. Significant progresses were achieved in understanding the analytical computations of multi-loop Feynman integrals in recent years. In this talk, I will present some of our recent works on the analytic calculations of Feynman integrals, which are based on the method of differential equations along with the choice of canonical basis.