Majorana Higgses at colliders

TL;DR

This paper explores collider signatures of Majorana neutrino mass origins within the minimal Left-Right symmetric model, focusing on Higgs triplet production and decay modes at the LHC and future colliders, highlighting novel lepton number violating signals.

Contribution

It introduces new collider search strategies for Majorana Higgs triplets, including displaced vertex signatures and lepton number violation, extending sensitivity beyond 10 TeV.

Findings

Higgs triplet $ o$ heavy neutrino pair production at LHC

Lepton number violation signals with no significant background

Sensitivity to Left-Right breaking scale beyond 10 TeV

Abstract

Collider signals of heavy Majorana neutrino mass origin are studied in the minimal Left-Right symmetric model, where their mass is generated spontaneously together with the breaking of lepton number. The right-handed triplet Higgs boson $\Delta$, responsible for such breaking, can be copiously produced at the LHC through the Higgs portal in the gluon fusion and less so in gauge mediated channels. At $\Delta$ masses below the opening of the $VV$ decay channel, the two observable modes are pair-production of heavy neutrinos via the triplet gluon fusion $gg \to \Delta \to NN$ and pair production of triplets from the Higgs $h \to \Delta \Delta \to 4N$ decay. The latter features tri- and quad same-sign lepton final states that break lepton number by four units and have no significant background. In both cases up to four displaced vertices may be present and their displacement may serve as a discriminating variable. The backgrounds at the LHC, including the jet fake rate, are estimated and the resulting sensitivity to the Left-Right breaking scale extends well beyond 10 TeV. In addition, sub-dominant radiative modes are surveyed: the $\gamma \gamma$, $Z \gamma$ and lepton flavour violating ones. Finally, prospects for $\Delta$ signals at future $e^+ e^-$ colliders are presented.