Pseudo-Nambu-Goldstone bosons (pNGBs) are naturally light, spin-zero particles that can be interesting dark-matter (DM) candidates. We study the phenomenology of a pNGBΘ associated with an approximate symmetry of the neutrino seesaw sector. A small coupling of Θ to the Higgs boson is induced radiatively by the neutrino Yukawa couplings. By virtue of this Higgs-portal interaction, (i) the pNGB acquires a mass m Θ proportional to the electroweak scale, and (ii) the observed DM relic density can be generated by the freeze-in of Θ particles with mass m Θ ~ 3 MeV. Alternatively, the coupling of Θ to heavy sterile neutrinos can account for the DM relic density, in the window 1 keV ≤ m Θ ≤ 3 MeV. The decays of Θ into light fermions are suppressed by the seesaw scale, making such pNGBs sufficiently stable to play the role of DM.
|Journal||Physical Review X|
|Publication status||Published - 1 Dec 2011|
- Particles and fields