论文标题
与手性的自动化散射幅度
Automating scattering amplitudes with chirality flow
论文作者
论文摘要
最近，我们介绍了手学流动形式主义，这种方法是基于纺纱形式形式主义的一种方法，灵感来自QCD中的颜色流构想。有了这种形式主义，Feynman的规则和图表被简化，以至于通常可以手工立即写下螺旋性幅度，从而给出了Feynman图。在本文中，我们表明该方法还可以通过考虑$ e^+ e^ - $在基于Madgraph的树级实现的$ n $光子上来加快对散射幅度的数值评估。我们发现，计算时间大约减少了六个光子的十倍，并且比默认的MADGRAPH5_AMC@nlo实现的外部粒子数量更好。这种性能增益部分归因于涉及更紧凑的Lorentz结构，部分原因是透明选择量规参考向量的透明选择减少了所考虑的Feynman图。
Recently we introduced the chirality-flow formalism, a method which builds on the spinor-helicity formalism and is inspired by the color-flow idea in QCD. With this formalism, Feynman rules and diagrams are simplified to the extent that it is often possible to immediately, by hand, write down a helicity amplitude given a Feynman diagram. In this paper we show that the method can also speed up numerical evaluation of scattering amplitudes by considering $e^+ e^-$ going to $n$ photons in a MadGraph-based tree-level implementation. We find that the computation time is reduced by roughly a factor ten for six photons, and that it scales better with the number of external particles than the default MadGraph5_aMC@NLO implementation. This performance gain is in part attributed to the more compact Lorentz structures involved, and in part due to a transparent choice of gauge reference vectors which reduces the number of Feynman diagrams considered.
