Inverse Neutrino-less Double Beta Decay Revisited: Neutrinos, Higgs Triplets and a Muon Collider

TL;DR

This paper explores the potential of future linear and muon colliders to detect inverse neutrino-less double beta decay via heavy neutrino and Higgs triplet exchange, providing new insights into neutrino mass mechanisms and collider sensitivities.

Contribution

It offers a comprehensive analysis of inverse neutrino-less double beta decay at colliders, including the effects of heavy neutrinos and Higgs triplets, and establishes a see-saw relation linking low-energy data with high-energy parameters.

Findings

Heavy neutrino exchange can be probed up to 10^6 GeV at e-e colliders.

Muon colliders have limited sensitivity due to mixing constraints.

Observable signals for Higgs triplets require narrow resonances.

Abstract

We revisit the process of inverse neutrino-less double beta decay (e e -> W W) at future linear colliders. The cases of Majorana neutrino and Higgs triplet exchange are considered. We also discuss the processes e mu -> W W and mu mu -> W W, which are motivated by the possibility of muon colliders. For heavy neutrino exchange and center-of-mass energies larger than 1 TeV, we show that masses up to 10^6 (10^5) GeV could be probed for e-e and e-mu machines, respectively. The stringent limits for mixing of heavy neutrinos with muons render mu mu -> W W less promising, even though this process is not constrained by limits from neutrino-less double beta decay. If Higgs triplets are responsible for inverse neutrino-less double beta decay, observable signals are only possible if a very narrow resonance is met. We also consider unitarity aspects of the process in case both Higgs triplets and neutrinos are exchanged. An exact see-saw relation connecting low energy data with heavy neutrino and triplet parameters is found.