The Majoron Cosmological Window: Dark Matter and Thermal Leptogenesis

TL;DR

This paper explores how the majoron, a particle linked to neutrino mass and symmetry breaking, can serve as dark matter and facilitate leptogenesis, with future telescopes potentially testing this scenario.

Contribution

It identifies a cosmologically viable parameter space where majoron dark matter and high-scale leptogenesis coexist, linking particle physics with cosmological observations.

Findings

Majoron can account for dark matter via freeze-in production.

High-scale leptogenesis constrains majoron properties and abundance.

Future telescopes can probe parts of the majoron parameter space.

Abstract

The majoron is the Nambu-Goldstone boson associated with the spontaneous breaking of a global $B-L$ symmetry. Remarkably, the minimal majoron framework can simultaneously address three key empirical indications of physics beyond the Standard Model: neutrino masses, the matter-antimatter asymmetry, and dark matter. In this work, we identify the cosmologically viable region in which majoron dark matter and high-scale thermal leptogenesis can be realised simultaneously. We show that successful leptogenesis plays a central role in making this scenario predictive: by constraining the right-handed-neutrino mass scale, it determines the irreducible freeze-in contribution to the majoron abundance and fixes the size of the couplings relevant for visible dark matter decays. Combining the irreducible dark matter production mechanisms with warm dark matter limits and indirect searches for decaying dark matter, we map the resulting majoron cosmological window and show that future X- and gamma-ray telescopes can probe part of the surviving parameter space.