Heavy Majorana neutrinos from Wγ fusion at hadron colliders

Abstract

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 W γ → N ℓ ± . 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 ′ → W * → N ℓ ± at NNLO in QCD, we find that the W γ fusion process becomes relatively more important at higher scales, surpassing the DY mechanism at m N ∼ 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 |V µN | 2 < 6 × 10 −3 , a 5σ discovery can be made via the same-sign dimuon channel for m N = 530 (1070) GeV at the 14 TeV LHC (100 TeV VLHC) after 1 ab −1 . Reversely, for m N = 500 GeV and the same integrated luminosity, a mixing |V µN | 2 of the order 1.1 × 10 −3 (2.5 × 10 −4 ) may be probed.

Fully automated precision predictions for heavy neutrino production mechanisms at hadron colliders

“…At 14 (100) TeV, the VBF rate surpasses the CC DY rate at m N ≈ 850 (1100) GeV. This somewhat differs from [38] and can be traced to the different γ-PDFs used: at large (small) scales of τ = m 2 N /s, the qγ luminosity here is larger (smaller) than in [38], leading to VBF overtaking the DY CC at smaller (larger) values of m N . However, present-day γ-PDF uncertainties are sizable [60,71].…”

“…(13) for N ℓ ± + nj, gives rise to logarithms of the form [38] Here, p jγ T is the p T of the jet associated with the photon exchange. However, consistent treatment of Eq.…”

“…and has recently been found to be subleading in parts of this mass regime [37,38]. Missing in most analyses is the gluon fusion (GF) channel [37], which proceeds at leading order (LO) through quark triangles in Fig.…”

“…Recent analyses have investigated the sizable EW vector boson fusion (VBF) process [38,[41][42][43][44][45][46]:…”

Neutrino masses from neutral top partners

“…A related study in the context of the inverse seesaw embedded within the next-to-minimal supersymmetric standard model (NMSSM) finds that it may be possible to detect the heavy RHN at the LHC in the trilepton þ MET final state with suitable cuts applied [81]; however, this was for M N ¼ 100 GeV which has a much larger production cross section. We note that striking collider signatures of lepton-number violation [83][84][85][86][87][88][89][90] are suppressed in our scenario by the small collective breaking of the lepton number.…”