The Majoron at two loops

TL;DR

This paper calculates two-loop couplings of the Majoron to Standard Model particles, exploring phenomenological constraints and emphasizing lepton-flavor-violating decays as key experimental signatures.

Contribution

It provides the first detailed two-loop level analysis of Majoron couplings, including gauge and flavor-changing interactions, within the seesaw framework.

Findings

Majoron couplings to gauge bosons are quantified.

Constraints on Majoron production and decay are analyzed.

Lepton-flavor-violating decays are highlighted as promising search channels.

Abstract

We present singlet-Majoron couplings to Standard Model particles through two loops at leading order in the seesaw expansion, including couplings to gauge bosons as well as flavor-changing quark interactions. We discuss and compare the relevant phenomenological constraints on Majoron production as well as decaying Majoron dark matter. A comparison with standard seesaw observables in low-scale settings highlights the importance of searches for lepton-flavor-violating two-body decays $\ell \to \ell' +$Majoron in both the muon and tau sectors.