Leptogenesis driven by majoron

Abstract

We propose a leptogenesis scenario where baryon asymmetry generation is assisted by the kinetic motion of the majoron, $J$, in the process of lepton-number violating inverse decays of a right-handed neutrino, $N$. We investigate two distinct scenarios depending on the sources of majoron kinetic motion: 1) the misalignment mechanism, and 2) the kinetic misalignment mechanism. The former case can naturally generate the observed baryon asymmetry for the majoron mass $m_J\gtrsim \mathrm{TeV}$ and the right-handed neutrino's mass $M_N\gtrsim 10^{11}\mathrm{GeV}$. However, an additional decay channel of the majoron is required to avoid the overclosure problem of the majoron oscillation. The later scenario works successfully for $m_J\lesssim 100\mathrm{keV}$, and $M_N\lesssim 10^9\mathrm{GeV}$ while $M_N$ can be even far below the temperature of the electroweak phase transition as long as sufficiently large kinetic misalignment is provided. We also find that a sub-$100\mathrm{keV}$ majoron is a viable candidate for dark matter.

Comments: 10 pages, 4 figures; V2: version accepted in PRD