Implementation of Angularly Ordered Electroweak Parton Shower in Herwig 7

TL;DR

This paper details the implementation and testing of an angularly ordered electroweak parton shower in Herwig 7, enhancing simulation accuracy for high-energy collider events involving electroweak bosons.

Contribution

The paper introduces a novel electroweak parton shower algorithm in Herwig 7, including helicity-dependent functions and initial-state radiation, validated through performance tests and comparison with LHC data.

Findings

Successful embedding of EW shower in Herwig 7

Accurate predictions of W boson angular distributions

Agreement with ATLAS data and underlying event simulations

Abstract

We discuss the necessary steps for implementing an angularly ordered (AO) electroweak (EW) parton shower in Herwig 7 multi-purpose event generator. This includes calculating the helicity-dependent quasi-collinear EW branching functions that correspond to the full range of final-state EW parton shower, in addition to the initial-state EW gauge vector boson radiations. The results are successfully embedded in the AO Herwig 7 shower algorithm and have undergone a set of comprehensive and conclusive performance tests. Furthermore, we have used this EW parton shower algorithm, alongside the existing $QCD+QED$ AO shower, to predict the angular distributions of $W^{\pm}$ bosons in LHC events with high transverse momentum jets. These results are compared against the explicitly generated underlying events as well as the existing ATLAS data to show the effectiveness of the newly implemented $QCD+QED+EW$ AO parton shower scheme.