Heavy Majorana neutrinos from Wγ fusion at hadron colliders

Vector boson fusion processes become increasingly more important at higher collider energies and for probing larger mass scales due to collinear logarithmic enhancements of the cross section. In this context, we revisit the production of a hypothetic heavy Majorana neutrino (N) at hadron colliders. Particular attention is paid to the fusion process Wγ → Nℓ±. We systematically categorize the contributions from a photon initial state in the elastic, inelastic, and deeply inelastic channels. Comparing with the leading channel via the Drell-Yan production qq¯′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ q{\overline{q}}^{\prime } $$\end{document}→ W*→ Nℓ± at NNLO in QCD, we find that the Wγ fusion process becomes relatively more important at higher scales, surpassing the DY mechanism at mN ∼ 1 TeV (770 GeV), at the 14 TeV LHC (100 TeV VLHC). We investigate the inclusive heavy Majorana neutrino signal, including QCD corrections, and quantify the Standard Model backgrounds at future hadron colliders. We conclude that, with the currently allowed mixing |VμN|2 < 6 × 10−3, a 5σ discovery can be made via the same-sign dimuon channel for mN = 530 (1070) GeV at the 14 TeV LHC (100 TeV VLHC) after 1 ab−1. Reversely, for mN = 500 GeV and the same integrated luminosity, a mixing |VμN|2 of the order 1.1 × 10−3 (2.5 × 10−4) may be probed.