Paper detail

NLO electroweak and QCD corrections to the production of a photon with three charged lepton plus missing energy at the LHC

Electroweak (EW) triboson production processes with at least one heavy gauge boson are of increasing interest at the Large Hadron Collider (LHC) as direct precision probes of one of the least-tested sectors of the Standard Model (SM), the quartic couplings of the EW gauge bosons. These processes therefore offer promising opportunities for searches for indirect signals of Beyond-the-SM (BSM) physics. In this paper, we present results for fiducial cross sections at next-to-leading-order (NLO) EW and NLO QCD to $p\;p\to e^{+}\;ν_{e}\;μ^{+}\;μ^{-}\;γ$ at the 13 TeV LHC. This signature includes the triboson production process $p\;p \to W^{+}\;Z\;γ$ with leptonic decays, $W^{+} \to e^{+}\;ν_{e}$ and $Z \to μ^{+}\;μ^{-}$. The computation is based on the complete set of leading-order (LO) contributions of $\mathcal{O}(α^5)$ and on NLO EW and NLO QCD cross sections of $\mathcal{O}(α^6)$ and $\mathcal{O}(α^5 α_\text{s})$, respectively, and thus off-shell effects, spin correlations and non-resonance contributions are fully taken into account. We construct a Monte Carlo framework which provides total and differential cross sections for a chosen set of basic analysis cuts. We find that while NLO EW corrections enhance the fiducial LO total cross section by only $1\%$, they can significantly change some distributions in certain kinematic regions. For example, the relative NLO EW corrections to the muon transverse momentum distribution at 500 GeV amounts to $-20\%$. To illustrate how missing NLO EW corrections could masquerade as BSM physics, we show examples for the impact of dimension-8 operators in the SM Effective Field Theory framework on selected kinematic distributions.