Tri-bimaximal mixing and the neutrino oscillation data

Abstract

Following recent results from the SNO solar neutrino experiment and the K2K long-baseline neutrino experiment, the combined existing data on neutrino oscillations now point strongly to a specific form for the lepton mixing matrix, with effective bimaximal mixing of ν µ and ν τ at the atmospheric scale and effective trimaximal mixing for ν e with ν µ and ν τ at the solar scale (hence 'tri-bimaximal' mixing). We give simple mass-matrices leading to tri-bimaximal mixing, and discuss its relation to the Fritzsch-Xing democratic ansatz.

Predicting neutrino parameters from SO(3) family symmetry and quark-lepton unification

“…We emphasise that, unlike [14], tri-bimaximal mixing in the neutrino sector is merely a staging point in our considerations, and the final form of the lepton mixing matrix, after charged lepton mixing angles have been taken into account, will not have the tri-bimaximal form. We therefore refer to this approach as tri-bimaximal complementarity to distinguish it from the usual tri-bimaximal neutrino mixing.…”

A model of lepton masses from a warped extra dimension

“…Indeed, we find that with appropriate choice of representations, the tri-bimaximal mixing pattern [18] characteristic of the A 4 symmetry can be reproduced by the leading order operators. Higher order terms can result in non-zero θ 13 , while maintaining the predictions for θ 12 , θ 23 within the experimentally allowed range.…”

“…We work in the basis of diagonal charged leptons which is obtained by performing the rotation on the entire left-handed doublet with V. Then, the light neutrino Majorana mass matrix is diagonalized by the Harrison-PerkinsScott (HPS) matrix [18] 14) corresponding to θ 13 = 0, sin 2 (2θ 12 ) = 8/9 and θ 23 = π/4. This tri-bimaximal mixing matrix is very close to the the best fit obtained from present oscillation data.…”

Interim Design Report

“…One guiding principle for precision measurements of neutrino oscillations should be the ability to provide unambiguous tests of these relations. An example is given by the tri-bimaximal mixing pattern (sin 2 θ 23 = 1/2, sin 2 θ 12 = 1/3, and sin 2 θ 13 = 0) [28]; a popular, zeroth-order ansatz that guides theoretical research in neutrino flavour. Different models make different predictions regarding deviations from this ansatz, which are usually small and proportional to some other small parameters in flavour physics.…”