Implementation of Angularly Ordered Electroweak Parton Shower in Herwig 7

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.

26 pages, 15 figures and 4 tables

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• Dark Sector Showers and Hadronisation in Herwig 7
• Generalized angular-order parton showers in Herwig 7
• Towards a Fully Automated Differential ${\text{NNLO}}_{\text{EW}}$ Generator for Lepton Colliders
• The Forward Physics Facility at the High-Luminosity LHC
• Monte Carlo Event Generators
• Polarization and kinematic properties of the splitting functions $q\to W^{\pm }+q^{\prime }$ and $q\to Z^0+q$