Gravitational echoes of lepton number symmetry breaking with light and ultralight Majorons

TL;DR

This paper introduces a low-scale Majoron model with an inverse seesaw mechanism that predicts light and ultralight Majorons, neutrino properties, and strong cosmological phase transitions, which could produce detectable gravitational waves.

Contribution

It presents a novel Majoron model with dimension-6 operators enabling simultaneous light Majorons, neutrino mixing, and strong phase transitions, linking particle physics with gravitational wave signals.

Findings

Model predicts strong first-order phase transitions in the early universe.

Potential gravitational wave signals detectable by LISA and other observatories.

Parameter space consistent with collider physics constraints.

Abstract

We formulate a version of the low-scale Majoron model equipped with an inverse seesaw mechanism featuring lepton-number preserving dimension-6 operators in the scalar potential. Contrary to its dimension-4 counterpart, we find that the model can simultaneously provide light and ultralight Majorons, neutrino masses and their mixing, while featuring strong first-order cosmological phase transitions associated to the spontaneous breaking of the lepton number and the electroweak symmetries in the early Universe. We show by a detailed numerical analysis that under certain conditions on the parameter space accounted for in collider physics, the model can be probed via the primordial gravitational wave spectrum potentially observable at LISA and other planned facilities.