ggxy: A flexible library to compute gluon-induced cross sections

We present the library ggxy, written in C++, which can be used to compute partonic and hadronic cross sections for gluon-induced processes with at least one closed heavy quark loop. It is based on analytic ingredients which avoids, to a large extent, expensive numerical integration. This results in significantly shorter run-times than other similar tools. Modifying input parameters, changing the renormalization scheme and varying renormalization and factorization scales is straightforward. In Version 1 of ggxy we implement all routines which are needed to compute partonic and hadronic cross sections for Higgs boson pair production up to next-to-leading order in QCD. We provide flexible interfaces and allow the user to interact with the built-in amplitudes at various levels.本研究推出一款基于C++编写的ggxy库，可用于计算至少包含一个闭合重夸克圈（closed heavy quark loop）的胶子诱导过程（gluon-induced processes）的部分子与强子截面（partonic and hadronic cross sections）。该库基于解析计算框架，可在极大程度上规避高成本的数值积分（numerical integration）运算，因此其运行时长相较其他同类工具显著缩短。修改输入参数、更换重整化方案（renormalization scheme）以及调整重整化标度（renormalization scale）与因子化标度（factorization scale）均十分简便。 在ggxy的1.0版本中，我们实现了所有可用于计算量子色动力学（Quantum Chromodynamics，QCD）框架下希格斯玻色子对产生（Higgs boson pair production）过程至次领头阶（next-to-leading order）的部分子与强子截面所需的程序模块。本库提供灵活的接口，允许用户在多个层级上与内置的散射振幅（amplitudes）进行交互。