Displaced Vertex and Disappearing Track Signatures in type-III Seesaw

TL;DR

This paper explores collider signatures of the type-III seesaw mechanism, focusing on displaced vertices and disappearing tracks from $SU(2)_L$ triplet fermions, and assesses detection prospects at HL-LHC, MATHUSLA, LHeC, and FCC-he.

Contribution

It provides a detailed analysis of how triplet fermions can be detected via specific signatures at various collider experiments, highlighting new detection channels for neutrino mass models.

Findings

Disappearing track signatures detectable at HL-LHC for fermion masses of a few hundred GeV.

Potential discovery of neutral triplet components at MATHUSLA for extremely light neutrino masses.

Charged triplet components observable as displaced vertices at LHeC and FCC-he.

Abstract

We investigate a prospect of probing the type-III seesaw neutrino mass generation mechanism at various collider experiments by searching for a disappearing track and a displaced vertex signature originating from the decay of $SU(2)_L$ triplet fermion ($\Sigma$). Since $\Sigma$ is primarily produced at colliders through the electroweak gauge interactions, its production rate is uniquely determined by its mass. We find that a $\Sigma$ particle with a mass of a few hundred GeV produces a disappearing track signature from the decay of its charged component, which can be searched at the HL-LHC. Furthermore, we show that if the lightest observed neutrino has a mass of around $10^{-9}$ eV, the neutral component of ${\Sigma}$ can be discovered at the proposed MATHUSLA detector. We also show that the charged component of ${\Sigma}$ with a mass of a few hundred GeV can be observed at the LHeC and FCC-he as a displaced vertex signature.