$\ exttt{Pyresias}$：如何编写一个部分子簇射
$\texttt{Pyresias}$: How to write a parton shower
AI总结：
本文提供构建正负电子湮灭末态辐射部分子簇射的实践教程，从共线因子化推导Sudakov概率，用否决算法和角序实现Pyresias程序，并与Herwig 7对比验证。
摘要：
我们提供了一个关于在正负电子湮灭中构建末态辐射部分子簇射的实践性入门教程。本教程面向具备微扰量子色动力学和Python基础知识的初学者。从共线因子化出发，我们推导了Sudakov不发射概率，并解释了否决算法如何生成连续的部分子分支。随后，我们通过角序引入颜色相干性，并重建末态动量，包括守恒能量和动量所需的反弹。随附的Python程序Pyresias分阶段开发这些要素：单夸克线、夸克-反夸克事件，以及包含夸克和胶子分裂的分支树。显式的采样公式、伪代码和练习将推导与实现联系起来。我们将否决算法与数值积分的不发射概率和首次发射分布进行测试，并在匹配的部分子级设置下，将重建事件与Herwig 7的角序簇射进行比较。这些比较在所述近似内提供了可复现的实现检查。教程还指出了排序变量、反弹和分支通道的选择如何与精密簇射开发相关联。
英文摘要：
We present a hands-on introduction to the construction of a parton shower for final-state radiation in electron-positron annihilation. The tutorial is intended for students with a basic knowledge of perturbative quantum chromodynamics and Python. Starting from collinear factorization, we derive the Sudakov no-emission probability and explain how the veto algorithm generates successive parton branchings. We then introduce colour coherence through angular ordering and reconstruct the final-state momenta, including the recoil needed to conserve energy and momentum. The accompanying Python program, Pyresias, develops these ingredients in stages: a single quark line, a quark-antiquark event, and a branching tree containing quark and gluon splittings. Explicit sampling formulae, pseudocode, and exercises connect the derivations to the implementation. We test the veto algorithm against the numerically integrated no-emission probability and first-emission distribution, and compare the reconstructed events with the angular-ordered shower of Herwig 7, using matching parton-level settings. These comparisons provide reproducible implementation checks within the stated approximations. The tutorial also identifies how choices of ordering variable, recoil, and branching channels connect to precision shower development.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
