- The paper introduces a novel automated generator for tree and one-loop amplitudes that integrates full SM corrections, covering both QCD and EW effects.
- It employs an innovative on-the-fly reduction algorithm that boosts computational speed by up to threefold while maintaining numerical stability.
- The method precisely handles multi-leg processes and QCD-EW interferences, setting a benchmark for advanced collider simulations and future NNLO extensions.
Overview of OpenLoops 2
The paper introduces "OpenLoops 2," a sophisticated automated generator for computing tree and one-loop scattering amplitudes that leverages an enhanced version of the open-loop recursion methodology. OpenLoops 2 marks a pivotal progression from its predecessor, primarily through its expansion to accommodate the full Standard Model (SM), incorporating electroweak (EW) corrections alongside the previously existing next-to-leading order (NLO) QCD computations. Critical features of this iteration include the systematic handling of QCD-EW interferences, an efficacious complex-mass scheme for unstable particles, enhanced management of on/off-shell external photons, and valuable improvements in computational scaling.
Expansion to Full Standard Model
A cornerstone of OpenLoops 2 is the extension from NLO QCD to encompass the entire Standard Model, incorporating comprehensive EW corrections resulting from gauge, Higgs, and Yukawa interactions. This development extends the functionality of OpenLoops beyond the confines of QCD, facilitating precise cross-section calculations and making high-energy collider predictions more robust by integrating both QCD and EW perturbations. The correct enumeration of QCD-EW interferences—a complex task given the continuous mixture of corrections at NLO—is thoroughly addressed, cementing the code's applicability to multifaceted physical processes.
Computational Enhancements
OpenLoops 2 is adorned with a newly proposed on-the-fly reduction algorithm that markedly elevates computational efficiency and stability. This novel approach supersedes external reduction libraries used for processing tree-loop interferences and interleaves loop creation and reduction, fostering lower tensorial rank and complexity. It amalgamates analytic methods typically constrained by Gram determinant instabilities and induces quadruple precision sparingly to manage instabilities dynamically, significantly boosting computation speed and stability without monopolizing CPU resources.
In practical terms, OpenLoops 2 presents substantial speed enhancements—up to threefold for complex multi-leg processes—compared to OL1. Notably, this processing advancement does not come at the cost of accuracy, as the hybrid precision system assures safe numerical stability even within challenging phase-space regions. This speedup, coupled with enhanced stability, primes OpenLoops 2 for application within demanding NLO and NNLO simulations, thoroughly extending its use in large-scale Monte Carlo frameworks and next-generation collider physics applications.
Implications and Future Developments
The practical implications of OpenLoops 2's advancements are substantial. Primarily, the tools developed can now tackle multi-particle SM processes with precision, essential for the ongoing and future analyses at the LHC and beyond. The handled accuracy in calculations paves the way for potentially integrating additional corrections, such as full NNLO EW effects or mixed QCD-EW NNLO calculations, which remain a crucial focus for achieving phenomenological precision.
Conclusively, OpenLoops 2 establishes a benchmark in amplitude computations, marrying efficiency with a comprehensive scope of SM corrections. It encapsulates a significant step forward in computational particle physics, prolific for its broad applicability and adaptability to various computational architectures and physical models, concurrently setting the stage for future enhancements and domain-specific customizations.