Axion-Inflation Baryogenesis via New U(1) gauge symmetries

Abstract

We investigate axion-inflation baryogenesis models, embedded into U(1) gauge symmetric extensions of the Standard Model (SM), in which the new gauge field couples to the pseudo-scalar inflaton via the Chern-Simons coupling. The motion of the inflaton induces a techyonic instability for one of the two helicities of the gauge field, resulting in the production of the helical gauge field. It further leads to the generation of the SM particle number densities via anomalies during the reheating, which is sufficient to generate the matter-antimatter asymmetry of the universe. Our numerical results show that this mechanism works for the $U(1)_{\mathbf L}$, $U(1)_{\mathbf R}$ and $U(1)_{\mathbf{B-L}}$ gauge symmetry cases, where subscripts ${\mathbf L}$, $\mathbf{R}$, $\mathbf{B-L}$ indicate the lepton number, the right-handed fermion and the baryon number minus the lepton number respectively. The key point for these mechanisms to work is that the evolution of the number density for right-handed neutrinos is decoupled from those of the SM particles, which shares the same merit as the Dirac Leptogenesis mechanism.