The majoron: a new dark matter candidate

Abstract

We review our recent proposal of the majoron as a suitable dark matter candidate. The majoron is the Goldstone boson associated with the spontaneous breaking of the ungauged lepton number, one of the mechanisms proposed for neutrino masses. The majoron can acquire a mass through quantum gravity efiects and can possibly account for the observed dark matter component of the Universe. The majoron dark matter scenario is consistent with the current observations of the cosmic microwave background anisotropy, provided that the lifetime of the majoron dark matter, ?, is greater than 250 Gyr. In the case of thermal production, the majoron should lie in the range 0:13 keV < mJ < 0:17 keV, although these limits are modifled in the non-thermal case. Applying this results to a given seesaw model for the generation of neutrino masses, the energy scale for the lepton number breaking phase transition is found to be constrained as EL & 10 6 GeV. We, thus, flnd that the majoron decaying dark matter (DDM) scenario flts nicely in models where neutrino masses arise a la seesaw and may lead to other possible cosmological implications.