# Unification with Vector-like fermions and signals at LHC

## TL;DR

This paper explores minimal Standard Model extensions with vector-like fermions that achieve gauge coupling unification, include neutrino mass mechanisms or dark matter candidates, and predict new particles detectable at the LHC.

## Contribution

It introduces new models with vector-like fermions for gauge unification, some of which incorporate neutrino masses or dark matter, and discusses their LHC signatures.

## Key findings

- Models achieve gauge coupling unification with vector-like fermions.
- Some models include Type III seesaw for neutrino masses.
- LHC searches already probe these particles around 1 TeV.

## Abstract

We look for minimal extensions of Standard Model with vector like fermions leading to precision unification of gauge couplings. Constraints from proton decay, Higgs stability and perturbativity are considered. The simplest models contain several copies of vector fermions in two different (incomplete) representations. Some of these models encompass Type III seesaw mechanism for neutrino masses whereas some others have a dark matter candidate. In all the models, at least one of the candidates has non-trivial representation under $SU(3)_{color}$. In the limit of vanishing Yukawa couplings, new QCD bound states are formed, which can be probed at LHC. The present limits based on results from 13 TeV already probe these particles for masses around a TeV. Similar models can be constructed with three or four vector representations, examples of which are presented.