Novel TeV-scale seesaw mechanism with Dirac mediators

TL;DR

This paper introduces a new TeV-scale seesaw mechanism involving Dirac mediators that generate neutrino masses, with potential testability at the LHC through specific signatures of heavy leptons.

Contribution

It presents a novel tree-level seesaw model with Dirac mediators in weak triplet and five-plet representations, leading to a new mass formula and testable predictions at collider energies.

Findings

Achieves neutrino masses ~ 0.1 eV with TeV-scale new states.

Identifies parameter space where tree-level contributions dominate.

Proposes LHC signatures for Dirac heavy leptons.

Abstract

We propose novel tree level seesaw mechanism with TeV-scale vectorlike Dirac mediators that produce Majorana masses of the known neutrinos. The gauge quantum number assignment to the Dirac mediators allows them to belong to a weak triplet and a five-plet of nonzero hypercharge. The latter leads to new seesaw formula m_\nu ~ v^6/M^5, so that the empirical masses m_\nu ~ 10^{-1} eV can be achieved by M ~ TeV new states. There is a limited range of the parameter space with M < a few 100 GeV where the tree level contribution dominates over the respective loop contributions and the proposed mechanism is testable at the LHC. We discuss specific signatures for Dirac type heavy leptons produced by Drell-Yan fusion at the LHC.