The Minimal Type-I Seesaw Model and Flavor-dependent Leptogenesis

Abstract

In this talk, we first give a brief review of the so-called minimal seesaw models and then concentrate on the minimal type-I seesaw model with two almost degenerate right-handed Majorana neutrinos of ${\cal O}(1 {\rm TeV})$. A specific texture of the neutrino Yukawa coupling matrix is proposed to achieve the nearly tri-bimaximal neutrino mixing pattern. This ansatz predicts (1) $θ^{}_{23} = π/4$, $|δ| = π/2$ and $\sin^2 θ^{}_{12} = (1 - 2 \tan^2 θ^{}_{13})/3$ in the $m^{}_1 = 0$ case; and (2) $θ^{}_{23} =π/4$ and $θ^{}_{13} = δ= 0$ in the $m^{}_3 = 0$ case. In both cases, the cosmological baryon number asymmetry can be explained via the resonant leptogenesis mechanism. Finally, we demonstrate the significance of flavor-dependent effects in our leptogenesis scenario.