Phenomenological Analysis of an $\mathrm{E}_{6}$-inspired Seesaw Model

TL;DR

This paper explores a neutrino mass model inspired by E6 GUT unification, predicting exotic particles at accessible energy scales and analyzing their phenomenological constraints and implications.

Contribution

It introduces a novel E6-inspired seesaw model with low-scale exotic neutrinos, vector-like fermions, and multiple Z' bosons, detailing their phenomenology and experimental bounds.

Findings

Z' boson mass > 2.8 TeV

Exotic quark mass > 1.3 TeV (stable) or 810 GeV (decaying)

Exotic lepton mass > 102 GeV

Abstract

We analyse the phenomenology of a model of neutrino masses inspired by $\mathrm{E}_{6}$ GUT unification in which the exotic neutrinos can be present at low scales. The model introduces vector-like isosinglet down-type quarks, vector-like isodoublet leptons, neutrino singlets and two $Z'$ bosons. The seesaw mechanism can be achieved with exotic neutrino masses as low as 100 GeV and Yukawa couplings of order $10^{-3}$. We find that the lightest $Z'$ boson mass is required to be above 2.8 TeV, the exotic quark masses are required to be above 1.3 TeV (810 GeV) if they are collider stable (promptly decaying), and the exotic lepton mass bounds remain at the LEP value of 102 GeV. The model also presents a type-II two-Higgs-doublet model (2HDM) along with two heavy singlet scalars. The 2HDM naturally has the alignment limit enforced thanks to the large VEVs of the exotic scalars, thereby avoiding most constraints.