Neutrino Symmetries from High to Low Scales

Proposed symmetry relations, e.g., quark-lepton complementarity (QLC) or tribimaximal mixing (TBM), need to be imposed at a high scale ∧ ∼ 1012 GeV characterising the large masses of right-handed neutrinos required to implement the seesaw mechanism. RG evolution down to the laboratory scale λ ∼ 103 GeV, generically prone to spoil these relations and their predicted neutrino mixing patterns, can be made to preserve them by appropriately constraining the Majorana phases α2,3. This is explicitly demonstrated in the MSSM for two versions of QLC and two versions of TBM. A preference for α2 ≃ π (i.e. m1 ≃ −m2) emerges in each case. Discrimination among the four cases is shown to be possible by future measurements of θ13.