OpenLoops 2
OpenLoops 2
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DOI：
10.1140/epjc/s10052-019-7306-2
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发表时间：
2019-10-01
影响因子：
4.4
通讯作者：
Zoller, Max F.
中科院分区：
文献类型：
--
作者：
Buccioni, Federico;Lang, Jean-Nicolas;Zoller, Max F.
我们提出了新版本的OpenLoops，一个自动生成器的树和一个循环的散射振幅的基础上的开环递归。OpenLoops 2的一个主要新奇是将原始算法从NLO QCD扩展到完整的标准模型，包括规范，Higgs和Yukawa相互作用的电弱（EW）修正。在这种情况下，在几个新的功能，我们讨论了QCD-EW干扰的系统簿记，一个灵活的实施复杂的质量计划的过程与壳和壳外不稳定粒子，壳和壳外外部光子的特殊处理，和有效的尺度变化。另一个主要的新奇是最近提出的飞行减少算法，它取代了使用外部减少库的计算树循环干扰的实施。这种新算法配备了一个自动化系统，通过分析方法结合新的混合精度方法，以最小的CPU开销高度有针对性地使用四倍精度，避免了革兰氏行列式的不稳定性。由此带来的速度和稳定性的显著提高尤其适用于具有挑战性的NLO多支计算和NNLO应用。
We present the new version of OpenLoops, an automated generator of tree and one-loop scattering amplitudes based on the open-loop recursion. One main novelty of OpenLoops 2 is the extension of the original algorithm from NLO QCD to the full Standard Model, including electroweak (EW) corrections from gauge, Higgs and Yukawa interactions. In this context, among several new features, we discuss the systematic bookkeeping of QCD-EW interferences, a flexible implementation of the complex-mass scheme for processes with on-shell and off-shell unstable particles, a special treatment of on-shell and off-shell external photons, and efficient scale variations. The other main novelty is the implementation of the recently proposed on-the-fly reduction algorithm, which supersedes the usage of external reduction libraries for the calculation of tree-loop interferences. This new algorithm is equipped with an automated system that avoids Gram-determinant instabilities through analytic methods in combination with a new hybrid-precision approach based on a highly targeted usage of quadruple precision with minimal CPU overhead. The resulting significant speed and stability improvements are especially relevant for challenging NLO multi-leg calculations and for NNLO applications.