MadSpin2：基于自旋密度矩阵形式论的重共振自旋纠缠衰变自动计算工具
MadSpin2: automated spin-entangled decays of heavy resonances via the spin-density matrix formalism
- Aristotle University of Thessaloniki（塞萨洛尼基亚里士多德大学）
- Université Catholique de Louvain（天主教鲁汶大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
MADSPIN2作为MADSPIN的新版本，基于自旋密度矩阵形式论，突破原工具限制，支持圈诱导过程等，拓宽了唯象学应用范围。
AI中文摘要：
对包含不稳定共振衰变产生的多个粒子的过程进行模拟，在领头阶及更高阶都面临计算挑战。本文介绍MADSPIN2，即专用工具MADSPIN的新版本，主要用于处理MG5AMC事例发生器产生的事例，解决上述问题。该版本仍基于Frixione-Laenen-Motylinski-Webber形式论，但利用自旋密度矩阵突破了此前实现的多数限制。它支持圈诱导过程、N体衰变以及由不同硬过程振幅间的振幅级干涉定义的事例，还引入了多极点近似和共振螺旋度分解，包含非对角螺旋度干涉贡献。这些进展大幅拓宽了MADSPIN的唯象学应用范围，使其可应用于该框架此前无法实现的场景，本文展示了其中若干应用案例。
英文摘要：
The simulation of processes that contain multiple particles from the decay of unstable resonances becomes computationally challenging both at leading order and beyond. This paper presents MADSPIN2, a new version of MADSPIN, a dedicated tool tackling this problem, primarily for events generated with the MG5AMC event generator. While still based on the Frixione-Laenen-Motylinski-Webber formalism, the new version leverages spin-density matrices to lift most of the limitations of the previous implementation. It supports loop-induced processes, N -body decays and samples defined by amplitude-level interference between distinct hard-process amplitudes. It also introduces the multiple-pole approximation and a resonance-helicity decomposition, including off-diagonal helicity-interference contributions. These developments substantially broaden the phenomenological scope of MADSPIN, enabling applications that were previously inaccessible within the framework, several of which are demonstrated in this work.
