W+W-, WZ and ZZ production in the POWHEG BOX

TL;DR

This paper details the implementation of vector boson pair production processes in the POWHEG framework, enabling more accurate simulations of these events at the LHC with inclusion of various interference effects and anomalous couplings.

Contribution

The paper introduces a comprehensive implementation of ZZ, W+W-, and WZ production in the POWHEG BOX, including interference effects and anomalous couplings, with code made publicly available.

Findings

All relevant contributions for four-lepton final states included

Interference between ZZ and W+W- is negligible

Anomalous couplings can be studied using the implementation

Abstract

We present an implementation of the vector boson pair production processes ZZ, W+W- and W Z within the POWHEG framework, which is a method that allows the interfacing of NLO calculations to shower Monte Carlo programs. The implementation is built within the POWHEG BOX package. The Z/\gamma^* interference, as well as singly resonant contributions, are properly included. We also considered interference terms arising from identical leptons in the final state. As a result, all contributions leading to the desired four-lepton system have been included in the calculation, with the sole exception of the interference between ZZ and W+W- in the production of a pair of same-flavour, oppositely charged fermions and a pair of neutrinos, which we show to be fully negligible. Anomalous trilinear couplings can be also set in the program, and we give some examples of their effect at the LHC. We have made the relevant code available at the POWHEG BOX web site.