Fully-Automated Precision Predictions for Heavy Neutrino Production Mechanisms at Hadron Colliders

Abstract

Motivated by TeV-scale neutrino mass models, we propose a systematic treatment of heavy neutrino $(N)$ production at hadron colliders. Our simple and efficient modeling of the vector boson fusion (VBF) $W^\pm\gamma\rightarrow N\ell^\pm$ and $N\ell^\pm+nj$ signal definitions resolve collinear and soft divergences that have plagued past studies, and is applicable to other color-singlet processes, e.g., associated Higgs $(W^\pm h)$, sparticle $(\tilde{\ell}^\pm\tilde{\nu_\ell})$, and charged Higgs $(h^{\pm\pm}h^{\mp})$ production. We present, for the first time, a comparison of all leading $N$ production modes, including both gluon fusion (GF) $gg\rightarrow Z^*/h^*\rightarrow N\overset{(-)}{\nu_\ell}$ and VBF. We obtain fully differential results up to next-to-leading order (NLO) in QCD accuracy using a Monte Carlo tool chain linking FeynRules, N{\small LO}CT, and MadGraph5\_aMC@NLO. Associated model files are publicly available. At the 14 TeV LHC, the leading order GF rate is small and comparable to the NLO $N\ell^\pm+1j$ rate; at a future 100 TeV Very Large Hadron Collider, GF dominates for $m_N={300-1500}$ GeV, beyond which VBF takes lead.