Next-to-tribimaximal mixing against CP violation and baryon asymmetry signs

Abstract

Four next-to-tribimaximal (NTBM) mixing patterns are widely considered as the feasible candidates for the observed leptonic mixing structure. With the recent measurements from T2K, as well as intensive global fits, the interval of $\sin\delta_{ CP} > 0$ for the Dirac CP-violating phase is persistently small in the normal ordering while $\sin\delta_{ CP} < 0$ is successively obtained up to $3\sigma$ level in the inverted ordering. In this paper, we advocate the fitting results of Dirac CP-violating phase as a constraint, and show that, it can basically rule out half of the regions allowed by the constraint from three mixing angles only. In addition, given the small $\sin\delta_{ CP} > 0$ interval, we find that a unique NTBM pattern can be selected out of the four candidates within $3\sigma$ uncertainty of the latest NuFIT 5.1, when the patterns are exposed to a Yukawa texture-independent leptogenesis for the baryon asymmetry of the Universe. For the surviving pattern, we find an interesting correlation between the Dirac CP-violating phase and the octant of atmospheric angle $\theta_{23}$ , where $\theta_{23}>45^\circ$ can be predicted once $5\pi/6 < \delta_{CP} <\pi$ in the normal ordering can be confirmed in the future measurements.