# Pseudo-Majoron as Light Mediator of Singlet Scalar Dark Matter

## TL;DR

This paper explores a light pseudoscalar mediator, called pseudo-majoron, arising from a neutrino mass model, which interacts with singlet scalar dark matter and evades current detection constraints.

## Contribution

It introduces a naturally light pseudoscalar mediator in the singlet-triplet majoron model that interacts with dark matter without conflicting with experimental bounds.

## Key findings

- The pseudoscalar decays mainly into neutrinos, avoiding CMB constraints.
- It mixes with the Higgs only at one loop, minimizing direct detection signals.
- The model provides a viable dark matter candidate with suppressed experimental signatures.

## Abstract

In the singlet-triplet majoron model of neutrino mass, lepton number is spontaneously broken. If it is also softly broken, then a naturally light pseudoscalar particle $\eta_I$ exists. It may then act as a light mediator for a real singlet scalar $\chi$ with odd dark parity. It is itself unstable, but decays dominantly to two neutrinos through its triplet scalar component, thereby not disturbing the cosmic microwave background (CMB). It also mixes with the standard-model Higgs boson only in one loop, thereby not contributing significantly to the elastic scattering of $\chi$ off nuclei in dark-matter direct-search experiments.