Lepton mixing patterns from combinations of elementary correlations

Recent data of reactor neutrino experiments set more stringent constraints on leptonic mixing patterns. We examine all possible patterns on the basis of combinations of elementary correlations of elements of leptonic mixing matrix. We obtain 62 viable mixing patters at 3σ level of mixing parameters. Most of these patterns can be paired via the μ-τ interchange which changes the octant of θ23 and the sign of cosδ. All viable patterns can be classified into two groups: the perturbative patterns and nonperturbative patterns. The former can be obtained from perturbing tri-bimaximal mixing. The latter cannot be obtained from perturbing any mixing pattern whose θ13 is zero. Different predictions of Dirac CP phase δ of these two types of mixing patterns are discussed. Evolutions of mass matrices of neutrinos with small mixing parameters are discussed via special mixing patterns on the basis of flavor groups. In general cases, a small variation of sinθ13 may bring about large modifications to alignment of vacuum expectation values in a mixing model. Therefore, small but nonzero sinθ13 brings a severer challenge to leptonic mixing models on the basis of flavor groups than usual views.

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29pages, 5 figures

14.60.Pq
14.60.St
neutrino: mixing
neutrino: mixing angle
neutrino: mass: hierarchy
neutrino: nuclear reactor
CP: violation
phase: CP
correlation
nonperturbative

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