NLO efforts in Herwig++

TL;DR

This paper discusses the integration of NLO QCD calculations into Herwig++ using the Matchbox framework, enabling automated, accurate simulations of complex particle interactions at NLO precision.

Contribution

It introduces the Matchbox framework in Herwig++ that automates NLO calculations and interfaces with one-loop matrix element providers, marking Herwig++'s first major release as version 7.

Findings

Enhanced NLO capabilities in Herwig++ with Matchbox

Automated setup for fixed NLO QCD calculations

Unified Herwig++ and HERWIG into a single major release

Abstract

With the advent and recent extension of the BLHA standard to interface Monte Carlo event generators and one-loop matrix element providers, the Herwig++ event generator has expanded its range of applicability to a multitude of underlying hard processes at NLO QCD. The new NLO development is centered around the Matchbox framework, which turns fixed NLO QCD calculations into parton shower matched calculations - to be matched to the two parton shower variants of Herwig++. Matchbox provides thereby for the automated setup of the underlying fixed NLO QCD calculations and the interface to the one-loop matrix element providers, as well as for an efficient and automated multi-channel phase space sampling, and forms the basis for the NLO capabilities of the new release of Herwig++. Along with several other new features and developments, the new release marks the end of distinguishing Herwig++ and (Fortran) HERWIG, and constitutes the first major release of version 7 of the Herwig event generator.