Majorons Revisited: light dark matter as FIMP

TL;DR

This paper explores how Majorons, arising from lepton number symmetry breaking, can serve as viable freeze-in dark matter within a simple Standard Model extension, linking neutrino physics to dark matter production.

Contribution

It demonstrates that Majorons can be freeze-in dark matter candidates in a minimal model with explicit lepton number breaking, connecting neutrino mass generation to dark matter.

Findings

Majorons can be viable keV-GeV dark matter via freeze-in.

Dark matter production is linked to right-handed neutrino annihilations.

The model extends the Standard Model minimally with singlet fields.

Abstract

We show that Majoron, the pseudo-Nambu-Goldstone boson resulting from the spontaneous breaking of global lepton number symmetry, can present itself as a viable freeze-in type of dark matter in a mass range keV-GeV, thanks to the explicit higher dimensional Lepton number breaking operator. Interestingly, the proposal is restricted within the simplest extension of the Standard Model with two singlet right-handed neutrinos and a singlet scalar so to address light neutrino mass and spontaneous breaking of lepton number symmetry respectively. The desired amount of Majoron production takes place from the annihilations of right-handed neutrinos indicating an intriguing connection between neutrino physics and dark matter.