Neutrino Masses at LHC: Minimal Lepton Flavour Violation in Type-III See-saw

TL;DR

This paper investigates the potential to detect minimal lepton flavour violation signatures of a Type-III see-saw model at the LHC, focusing on characteristic decay patterns and their relation to neutrino physics.

Contribution

It introduces a minimal lepton flavour violation framework within a Type-III see-saw model, linking collider signatures to neutrino mass and mixing parameters.

Findings

Fermionic triplet states can be observed up to 500 GeV at the LHC.

Characteristic decay signatures include suppressed lepton number violation and predictable lepton flavour composition.

Lepton flavour in final states can provide insights into neutrino mass ordering.

Abstract

We study the signatures of minimal lepton flavour violation in a simple Type-III see - saw model in which the flavour scale is given by the new fermion triplet mass and it can be naturally light enough to be produced at the LHC. In this model the flavour structure of the lepton number conserving couplings of the triplet fermions to the Standard Model leptons can be reconstructed from the neutrino mass matrix and the smallness of the neutrino mass is associated with a tiny violation of total lepton number. Characteristic signatures of this model include suppressed lepton number violation decays of the triplet fermions, absence of displaced vertices in their decays and predictable lepton flavour composition of the states produced in their decays. We study the observability of these signals in the processes $pp\rightarrow 3\ell + 2j +\Sla{E_T}$ and $pp\rightarrow 2\ell + 4j$ with $\ell =e$ or $\mu$ taking into account the present low energy data on neutrino physics and the corresponding Standard Model backgrounds. Our results indicate that the new fermionic states can be observed for masses up to 500 GeV depending on the CP violating Majorana phase for an integrated luminosity of 30 fb$^{-1}$. Moreover, the flavour of the final state leptons in the above processes can shed light on the neutrino mass ordering.