[论文解读] Looking inside jets: an introduction to jet substructure and boosted-object phenomenology

Simone Marzani, Grégory Soyez+1 more|arXiv (Cornell University)|Jan 29, 2019

High-Energy Particle Collisions Research被引用 58

一句话总结

一套教学性质的讲义，介绍喷流子结构、修剪（grooming）以及在量子色动力学中增强对象的现象学，强调理论、可观测量及在LHC上的应用。

ABSTRACT

The study of the internal structure of hadronic jets has become in recent years a very active area of research in particle physics. Jet substructure techniques are increasingly used in experimental analyses by the LHC collaborations, both in the context of searching for new physics and for Standard Model measurements. On the theory side, the quest for a deeper understanding of jet substructure algorithms has contributed to a renewed interest in all-order calculations in QCD. This has resulted in new ideas about how to design better observables and how to provide a solid theoretical description for them. In the last years, jet substructure has seen its scope extended, for example, with an increasing impact in the study of heavy-ion collisions, or with the exploration of deep-learning techniques. Furthermore, jet physics is an area in which experimental and theoretical approaches meet together, where cross-pollination and collaboration between the two communities often bear the fruits of innovative techniques. Despite the wealth of literature on this topic, we feel that a comprehensive and, at the same time, pedagogical introduction to jet substructure is still missing. This makes the endeavour of approaching the field particularly hard, as newcomers have to digest an increasing number of substructure algorithms and techniques, too often characterised by opaque terminology and jargon. Furthermore, while first-principle calculations in QCD have successfully been applied in order to understand and characterise the substructure of jets, they often make use of calculational techniques, such as resummation, which are not the usual textbook material. Thus, the idea of combining our experience in different aspects of jet substructure phenomenology to put together this set of lecture notes, which we hope could help and guide someone who moves their first steps in the physics of jet substructure.

研究动机与目标

• 激发研究喷流子结构，作为区分提升的电弱尺度共振子与QCD喷流的工具。
• 提供一个自包含、教学性强的关于对喷流物理学相关的在对撞机上的QCD导论。
• 概述用于分析喷流内部结构的喷流算法、修剪技巧和观测量。
• 给出解析和蒙特卡洛比较，以理解喷流质量分布及修剪的影响。
• 强调在搜索、测量以及理论与实验接口方面的应用。

提出的方法

• 回顾与喷流相关的软/共线极限中的QCD理论和因子化。
• 解释摄动计算以及IRC 安全性在喷流观测量中的作用。
• 讨论喷流算法（序贯重组和圆锥算法）及实验因素。
• 分析带修剪与不带修剪的喷流质量分布，以说明全阶重排（all-order resummation）概念。
• 介绍子结构工具（修剪器、分支检测器、喷流形状观测量）及其解析理解。
• 将解析预测与蒙特卡洛模拟进行比较，以评估非扰动效应。

实验结果

研究问题

• RQ1 喷流子结构观测量在QCD的软/共线极限下如何进行解析理解？
• RQ2 修剪技术对喷流质量分布及相关观测量的影响是什么？
• RQ3 修剪和子结构工具如何实现来自提升共振的信号喷流与背景QCD喷流的区分？
• RQ4 重排与因子化方法（如相干分支、SCET）在描述喷流观测量中的作用是什么？
• RQ5 如何将喷流子结构方法稳健地应用于LHC的搜索和测量？

主要发现

• 喷流子结构技术已经成为LHC分析中用于搜索和标准模型测量的核心。
• 修剪降低对软解耦非撓性效应的敏感性，便于与第一性原理计算进行比较。
• 在修剪下对喷流质量分布的解析理解展示了全阶重排与非扰性修正的相互作用。
• 夸克/胶子判别和多分支标记可以在解析框架内通过角度量、ECFs及相关观测量来研究。
• 子结构方法不仅限于增强玻色子，也延伸至重离子物理和新型机器学习方法。