New Production Mechanism for Heavy Neutrinos at the LHC

TL;DR

This paper introduces a dominant new production mechanism for heavy neutrinos at the LHC, based on $t$-channel $W ext{ } ext{ extgamma}$-fusion, which enhances experimental search sensitivity for neutrino masses above 100 GeV.

Contribution

The study identifies and analyzes a new $t$-channel $W ext{ extgamma}$-fusion process that surpasses traditional $s$-channel production for heavy neutrinos, improving search strategies.

Findings

New production mechanism dominates for neutrino masses >100 GeV.

Significantly improved collider limits on neutrino mixing.

Potential extension to other exotic particle searches.

Abstract

We study a new production mechanism for heavy neutrinos at the LHC, which dominates over the usually considered $s$-channel $W$-exchange diagram for heavy-neutrino masses larger than 100 - 200 GeV. The new mechanism is infrared-enhanced by $t$-channel $W\gamma$-fusion processes. This has important implications for experimental tests of the seesaw mechanism of neutrino masses, and in particular, for the ongoing heavy neutrino searches at the LHC. We find that the direct collider limits on the light-to-heavy neutrino mixing can be significantly improved, when this new production channel is properly taken into account. The scope of this new mechanism can equally well be extended to other exotic searches at the LHC.