Nonzero |U_e3| from Charged Lepton Corrections and the Atmospheric Neutrino Mixing Angle

TL;DR

This paper explores how charged lepton corrections can generate a nonzero |U_e3| and affect the atmospheric neutrino mixing angle, providing predictions consistent with recent neutrino oscillation data.

Contribution

It systematically analyzes minimal forms of charged lepton mixing matrices that produce observed neutrino mixing angles, considering different neutrino mixing patterns and orderings.

Findings

Predicts Dirac CP phase  around  for BM and LC cases

Identifies /2 or 3/2 for TBM case, excluding CP conserving values at >4

Shows results depend strongly on the ordering of rotations in U_e

Abstract

After the successful determination of the reactor neutrino mixing angle \theta_13 ~ 0.16 \neq 0, a new feature suggested by the current neutrino oscillation data is a sizeable deviation of the atmospheric neutrino mixing angle \theta_23 from \pi/4. Using the fact that the neutrino mixing matrix U = U_e^\dagger U_\nu, where U_e and U_\nu result from the diagonalisation of the charged lepton and neutrino mass matrices, and assuming that U_\nu has a i) bimaximal (BM), ii) tri-bimaximal (TBM) form, or else iii) corresponds to the conservation of the lepton charge L' = L_e - L_\mu - L_\tau (LC), we investigate quantitatively what are the minimal forms of U_e, in terms of angles and phases it contains, that can provide the requisite corrections to U_\nu so that \theta_13, \theta_23 and the solar neutrino mixing angle \theta_12 have values compatible with the current data. Two possible orderings of the 12 and the 23 rotations in U_e, "standard" and "inverse", are considered. The results we obtain depend strongly on the type of ordering. In the case of "standard" ordering, in particular, the Dirac CP violation phase \delta, present in U, is predicted to have a value in a narrow interval around i) \delta ~ \pi in the BM (or LC) case, ii) \delta ~ 3\pi/2 or \pi/2 in the TBM case, the CP conserving values \delta = 0, \pi, 2\pi being excluded in the TBM case at more than 4\sigma. In the addendum we discuss the implications of the latest 2013 data.