Testing New TeV-scale Seesaw Mediators at the LHC

TL;DR

This paper introduces a novel TeV-scale seesaw mechanism involving Dirac fermions and a weak five-plet, which can generate neutrino masses and be tested at the LHC through characteristic decay signatures.

Contribution

It presents a new seesaw model with a weak five-plet leading to a unique mass formula and explores its testability at the LHC for certain parameter ranges.

Findings

Neutrino masses are explained by a new seesaw formula m_ν ~ v^6/M^5.

The model predicts observable signatures at the LHC for M < a few 100 GeV.

Characteristic decays of heavy leptons can be used to test the mechanism.

Abstract

We propose TeV-scale Dirac fermions producing Majorana masses of the known neutrinos via tree-level seesaw, different from standard type I and III seesaw. The employed weak five-plet with nonzero hypercharge leads to new seesaw formula m_\nu ~ v^6/M^5 and to empirical masses m_\nu ~ 10^{-1} eV for M ~ TeV new states. For a limited range of the parameter space, where M < a few 100 GeV, the proposed mechanism is testable at the LHC via characteristic decays of Dirac type heavy leptons, produced by a Drell-Yan fusion.