Abstract

In this paper, we revisit the dimension-7 neutrino mass generation mechanism based on the addition of an isospin $3/2$ scalar quadruplet and two vector-like iso-triplet leptons to the standard model. We discuss the LHC phenomenology of the charged scalars of this model, complemented by the electroweak precision and lepton flavor violation constraints. We pay particular attention to the triply charged and doubly charged components. We focus on the same-sign-tri-lepton signatures originating from the triply-charged scalars and find a discovery reach of 600 - 950 GeV at 3 ab$^{-1}$ of integrated luminosity at the LHC. On the other hand, doubly charged Higgs has been an object of collider searches for a long time, and we show how the present bounds on its mass depend on the particle spectrum of the theory. Strong constraint on the model parameter space can arise from the measured decay rate of the Standard Model Higgs to a pair of photons as well.

Highlights

  • The remarkable discovery of the 125 GeV scalar particle by the CMS and ATLAS collaborations [1,2] is the crowning achievement of the Run-I of the LHC

  • The simplest way to achieve that goal is via an effective dimension-5 operator, LLHH=M [4], where H is the standard model (SM) Higgs doublet, L is the left-handed lepton doublet, and M is the scale of new physics

  • We demonstrate that for our realistic benchmark points (BP) the proper decay length of doubly and triply charged Higgs bosons are quite large in regions of the parameter space, and we discuss when they will be beyond the scope of prompt lepton searches performed at the LHC

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Summary

INTRODUCTION

The remarkable discovery of the 125 GeV scalar particle by the CMS and ATLAS collaborations [1,2] is the crowning achievement of the Run-I of the LHC. The simplest way to achieve that goal is via an effective dimension-5 operator, LLHH=M [4], where H is the SM Higgs doublet, L is the left-handed lepton doublet, and M is the scale of new physics Under this mechanism, neutrinos acquire a mass mν ∼ v2=M, with v being the vacuum expectation value (VEV) of H. We would like to point out that the LHC experiments traditionally show their bound on doubly charged Higgs particle mass in same-sign dilepton final states assuming a 100% branching ratio (BR) for particular flavor combinations. Instead, we reinterpret their results using realistic benchmark points (BP), consistent with neutrino oscillation data, and show that the constraints on doubly charged Higgs mass can be relaxed.

MODEL AND FORMALISM
Higgs sector of the model
Boundedness of the Higgs potential
Generation of neutrino mass
Neutrino mass hierarchies and Yukawa couplings
ELECTROWEAK PRECISION TESTS
CONSTRAINTS FROM LFV EXPERIMENTS
COLLIDER IMPLICATIONS
Production of ΔÆÆ and ΔÆÆÆ at the LHC
Decay of ΔÆÆ and ΔÆÆÆ
Searches for ΔÆÆ at the LHC
Signal of ΔÆÆÆ at the LHC
Findings
CONCLUSIONS
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