Large U_{e3} and Tri-bimaximal Mixing

Abstract

We investigate in a model-independent way to what extent one can perturb tri-bimaximal mixing in order to generate a sizable value of |U e3 |, while at the same time keeping solar neutrino mixing near its measured value, which is close to sin 2 θ 12 = 1 3 . Three straightforward breaking mechanisms to generate |U e3 | ≃ 0.1 are considered. For charged lepton corrections, the suppression of a sizable contribution to sin 2 θ 12 can be achieved if CP violation in neutrino oscillations is almost maximal. Generation of the indicated value of |U e3 | ≃ 0.1 through renormalization group corrections requires the neutrinos to be quasi-degenerate in mass. The consistency with the allowed range of sin 2 θ 12 together with large running of |U e3 | forces one of the Majorana phases to be close to π. This implies large cancellations in the effective Majorana mass governing neutrino-less double beta ((ββ) 0ν -)decay, constraining it to lie near its minimum allowed value of m 0 cos 2θ 12 , where m 0 > ∼ 0.1 eV. Finally, explicit breaking of the neutrino mass matrix in the inverted hierarchical and quasi-degenerate neutrino mass spectrum cases is similarly correlated with the (ββ) 0ν -decay effective Majorana mass, although to a lesser extent. The implied values for the atmospheric neutrino mixing angle θ 23 are given in all cases.

Possible alternatives to tri-bimaximal mixing

“…In principle one could perform for each scenario to be discussed in the following a dedicated analysis of perturbations in analogy, e.g., to the model-independent study for TBM in Ref. [14], or to studies for concrete models in Refs. [15].…”

Neutrino interactions in astrophysics and the third neutrino mixing angle θ[sub 13]

“…with a best fit value of 2.00 +2.09 −1.63 × 10 −2 [14]. One should note that it is not difficult to introduce theoretical models with such large values of θ 13 [15,16].…”

Renormalization Group Evolution of Neutrino Masses and Mixing in Seesaw Models

“…Some specific features of the RG evolution, like the stability of mixing angles and masses [66,91,92,93,94], possible occurrence of fixed points [95,96,97] have also been studied. RG induced deviations from various high scale symmetries like tri-bimaximal mixing scenario [64,65,98] or quark-lepton complementarity [63,65,100,101,102] and correlations with low scale observables have also been explored in detail.…”