Cogenesis by a sliding pNGB with symmetry non-restoration

Abstract: We show that a pseudo-Nambu-Goldstone boson (pNGB) with an initial misalignment angle can drive successful spontaneous baryogenesis, and become a good dark matter candidate if the corresponding global symmetry is non-restored at high temperatures. Considering a dimension-five explicit breaking operator, we find that the pNGB starts its motion with a sliding across rapidly decreasing potential barriers during which the baryon asymmetry is generated and frozen, and later it oscillates as dark matter. It is predicted that the pNGB mass and decay constant are around $5\,{\rm eV}$ and $3\times10^6\,{\rm GeV}$, respectively, while the radial mode has a light mass $O(10)\,{\rm MeV}$ and a small mixing $O(10^{-4})$ with the Higgs boson. Applied to the Majoron in the type-I seesaw model, the heaviest right-handed neutrino is required to be as light as $100\,{\rm GeV}$. These predictions can be tested at kaon experiments, heavy neutral lepton searches, LHC, and future colliders.