Tri-bimaximal neutrino mixing and flavor-dependent resonant leptogenesis

We propose a particularly economical neutrino mass model, in which there are only two right-handed Majorana neutrinos of O(1) TeV and their masses are highly degenerate. Its novel Yukawa-coupling texture together with the seesaw mechanism allows us to achieve the normal neutrino mass hierarchy with m1=0 and a nearly tri-bimaximal neutrino mixing pattern with the maximal CP-violating phase: θ23=π/4, |δ|=π/2 and sin2θ12=(1−2tan2θ13)/3. One may also obtain the inverted neutrino mass hierarchy with m3=0 and the corresponding neutrino mixing pattern with θ23=π/4 and θ13=δ=0. In both cases, it is possible to interpret the cosmological baryon number asymmetry ηB≈6.1×10−10 through the resonant leptogenesis mechanism. We demonstrate the significance of flavor-dependent effects in this leptogenesis scenario: they can either flip the sign of the flavor-independent prediction for ηB in the m1=0 case or magnify the magnitude of the flavor-independent prediction for ηB about 50 times in the m3=0 case.