Hunting for Heavy Majorana Neutrinos with Lepton Number Violating Signatures at LHC

TL;DR

This paper investigates the potential to discover heavy Majorana neutrinos through lepton number violating signatures at the LHC within the neutrinophilic two-Higgs-doublet model, identifying promising signals and setting exclusion limits.

Contribution

It provides a detailed simulation study of LNV signatures from cascade decays in the $ u$2HDM, highlighting the most promising channels for discovery at the LHC.

Findings

Same-sign trilepton signature is the most promising discovery channel.

Exclusion limits are set for $ u$2HDM parameters at 13 and 14 TeV LHC.

Distinct LNV signatures can be used to probe TeV-scale Majorana neutrinos.

Abstract

The neutrinophilic two-Higgs-doublet model ($\nu$2HDM) provides a natural way to generate tiny neutrino mass from interactions with the new doublet scalar $\Phi_\nu$ ($H^\pm,~H,~A$) and singlet neutrinos $N_R$ of TeV scale. In this paper, we perform detailed simulations for the lepton number violating (LNV) signatures at LHC arising from cascade decays of the new scalars and neutrinos with the mass order $m_{N_R}<m_{\Phi_\nu}$. Under constraints from lepton flavor violating processes and direct collider searches, their decay properties are explored and lead to three types of LNV signatures: $2\ell^\pm 4j+\cancel{E}_T$, $3\ell^\pm 4j+\cancel{E}_T$, and $3\ell^\pm\ell^\mp 4j$. We find that the same-sign trilepton signature $3\ell^\pm4j+\cancel{E}_T$ is quite unique and is the most promising discovery channel at the high-luminosity LHC. Our analysis also yields the $95\%$ C.L. exclusion limits in the plane of the $\Phi_\nu$ and $N_R$ masses at 13 (14) TeV LHC with an integrated luminosity of 100~(3000)/fb.