（ABSTRACT）

Although cosmological and astrophysical observations have found the baryon asymmetry of the universe, the standard model of particle physics hardly explain its origin, and thus new physics beyond the standard model is required. Leptogenesis is one of convincing models for baryogenesis, in which tiny neutrino masses can be explained by the presence of right-handed Majorana neutrinos via seesaw mechanism. There, Majorana masses of the right-handed neutrinos would be originated from spontaneous symmetry breaking of $U(1)_{B-L}$, which can lead to a Nambu-Goldstone boson called Majoron. We discuss a possiblitity that leptogenesis takes place in the primordial thermal bath due to the background Majoron field in motion.

（References)

・M.Ibe and K.Kaneta,“Spontaneous thermal Leptogenesis via Majoron oscillation,” arXiv:1504.04125 [hep-ph].