Matching N3LO QCD calculations to parton showers

TL;DR

This paper discusses methods for integrating third-order (N3LO) QCD calculations into parton shower simulations, enhancing the precision of collider physics predictions and proposing a toy model for future high-precision applications.

Contribution

It introduces a novel approach for matching N3LO fixed-order QCD calculations with parton showers, including a toy implementation and a new NNLO+PS formula for jet processes.

Findings

Developed a toy model for N3LO matching in $e^+e^- ightarrow u ar u$

Proposed a unitary matching method for embedding N3LO results into event generators

Derived a new NNLO+PS formula for processes with additional jets

Abstract

The search for new interactions and particles in high-energy collider physics relies on precise background predictions. This has led to many advances in combining precise fixed-order cross-section calculations with detailed event generator simulations. In recent years, fixed-order QCD calculations of inclusive cross sections at N3LO precision have emerged, followed by an impressive progress at producing differential results. Once differential results become publicly available, it would be prudent to embed these into event generators to allow the community to leverage these advances. This note offers some concrete thoughts on ME+PS matching at third order in QCD. As a method for testing these thoughts, a toy calculation of $e^+e^-\rightarrow u \bar u$ at $\mathcal{O}(\alpha_s^3)$ is constructed, and combined with an event generator through unitary matching. The toy implementation may serve also as blueprint for high-precision QCD predictions at future lepton colliders. As a byproduct of the N3LO matching formula, a new NNLO+PS formula for processes with "additional" jets is obtained.