Single top production in association with a $WZ$ pair at the LHC in the 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 $2\to 2$ 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 (${\mathcal{O}}_{tW}$,${\mathcal{O}}_{tZ}$,${\mathcal{O}}_{tG}$,${\mathcal{O}}_{\varphi Q}^{(-)}$,${\mathcal{O}}_{\varphi Q}^{(3)}$,${\mathcal{O}}_{\varphi t}$), also matching short-distance events to parton shower.

Comments: 33 pages with tables and figures. v2: minor typos are fixed. v3: minor typos are fixed, v4: minor typos are fixed, version accepted by JHEP