A study of a NLO matrix element generator for Wgamma and matching scheme for NLO events and PYTHIA parton shower

TL;DR

This paper compares a next-to-leading order (NLO) W gamma matrix element generator with leading order calculations in Pythia, introducing a matching scheme to combine NLO calculations with Pythia's parton shower for accurate event simulation.

Contribution

It presents a novel matching scheme that consistently combines NLO W gamma matrix elements with Pythia's parton shower, preserving rates and kinematic distributions.

Findings

The NLO package accurately produces W gamma+0 jet and W gamma+1 jet final states.

The matching scheme maintains the correct hard scattering rates.

Kinematic distributions of interest are preserved.

Abstract

We compare a NLO W gamma matrix element generator with the leading order calculation in Pythia . A matching scheme between a next-to-leading order W gamma matrix element generator by Baur et. al. and the Pythia parton shower is presented. The NLO package produces W gamma+0 jet and W gamma+1jet final states in the hard scattering and the objective is to consistently match these to the initial state radiation from Pythia parton shower. The proposed methodology preserves both the rate of the hard scattering process as well as various kinematic distributions of experimental interest.