Single top production in association with a $WZ$ pair at the LHC in the SMEFT

TL;DR

This paper investigates single top quark production with a WZ pair at the LHC within the Standard Model and SMEFT, highlighting its sensitivity to unitarity violations and providing detailed cross section predictions including dimension-6 operators.

Contribution

It introduces a reliable method to define tWZ production at NLO, separating it from overlapping processes, and provides comprehensive cross section results in SMEFT at 13 TeV.

Findings

Robust total and differential cross sections for tWZ at 13 TeV.

Validation of diagram-removal procedures for phase-space separation.

Sensitivity of tWZ to unitarity-violating effects in SMEFT.

Abstract

We study single top quark production in association with a $WZ$ pair at the LHC in the context of the Standard Model (SM) and the Standard Model Effective Field Theory (SMEFT). A significant advantage of $tWZ$ compared to other EW top production processes is its sensitivity to unitarity-violating behaviour induced in its $2\to2$ sub-amplitudes through modified EW interactions. At NLO in QCD, $tWZ$ interferes with $t\bar{t}Z$ and $t\bar{t}$ and a method to meaningfully separate it from these overlapping processes needs to be employed. In order to define $tWZ$ production for total rates and differential distributions, we consider the approaches proposed in the literature for similar cases and find that diagram-removal procedures provide reliable results both for the SM and the SMEFT in a suitably defined phase-space region. We provide robust results for total and differential cross sections for $tWZ$ at 13 TeV, including the six relevant dimension-6 operators ($\mathcal{O}_{tW}$,$\mathcal{O}_{tZ}$,$\mathcal{O}_{tG}$,$\mathcal{O}_{\phi Q}^{(-)}$,$\mathcal{O}_{\phi Q}^{(3)}$,$\mathcal{O}_{\phi t}$), also matching short-distance events to parton shower.