Charged Higgs induced 5 and 6 lepton signatures from heavy neutrinos at the LHC

TL;DR

This paper explores a new gauged U(1) extension of the Standard Model that predicts charged Higgs bosons decaying into heavy neutrinos and leptons, leading to distinctive 5 and 6 lepton signatures at the HL-LHC.

Contribution

It introduces a novel U(1) gauge extension with heavy neutrinos and charged Higgs bosons, analyzing their collider signatures and discovery potential at the HL-LHC.

Findings

5 and 6 lepton signals could be observed at HL-LHC with significant confidence

Charged Higgs pair production is enhanced by the Z' boson presence

Parameter regions with high significance are identified

Abstract

We propose an anomaly free gauged U$(1)$ extension of the SM where three right handed heavy neutrinos, being charged under the general U$(1)$ gauge group, are introduced to explain the origin of the tiny neutrino mass through the seesaw mechanism after the general U$(1)$ symmetry is broken. Due to the breaking of the general U$(1)$ symmetry a neutral beyond the standard model gauge boson $Z^\prime$ acquires mass. There are two Higgs doublets in this model where one interacts with the SM fermions and the other one interacts with the right handed heavy neutrinos and charged leptons. The charged multiplet of the second Higgs can completely decay into the heavy neutrinos and charged lepton in the neutrinophilic limit of the model parameters. The charged Higgs pair production can be influenced due to presence of the $Z^\prime$ boson at the High Luminosity LHC (HL-LHC) in addition to the neutral SM gauge bosons. The pair produced charged Higgs bosons decay into SM charged leptons and heavy neutrinos. Following the leading decay modes of the heavy neutrinos into charged leptons and $W$ boson we study the 5 and 6 lepton final states after the leptonic and hadronic decay of the $W$ bosons considering solely muons and electrons in the final state. Combining the electron and muon final states we estimate the significance of the 5 and 6 charged lepton processes in the $m_{H^\pm}-m_N$ plane for different benchmark points of $m_{Z^\prime}$. It is found that the 5 (6) charged lepton processes could be probed at the High Luminosity LHC (HL-LHC) with at least 5 (3) $\sigma$ significance and there are parameter regions where the significance could be larger.