Majoron

A Majoron is a hypothetical elementary particle proposed in particle physics, associated with the spontaneous violation of lepton number or B-L (Baryon number minus Lepton number) symmetry. Majorons are typically massless or very light bosons and often act as the Goldstone boson associated with this symmetry breaking.

The original motivation for the Majoron was to explain the small neutrino masses via the seesaw mechanism. In this context, the Majoron couples to neutrinos and can induce neutrinoless double beta decay. The detection of neutrinoless double beta decay would provide evidence for both Majorana neutrinos (neutrinos that are their own antiparticles) and possibly the existence of Majorons.

Various models predict different properties and interactions for Majorons, including their coupling to other particles and their potential to contribute to dark radiation. These models are actively researched and constrained by experimental data from neutrino experiments, collider searches, and cosmological observations.