Abstract
We consider schemes of neutrino mixing arising within the discrete symmetry approach to the well-known flavour problem. We concentrate on 3nu mixing schemes in which the cosine of the Dirac CP violation phase delta _{mathrm {CP}} satisfies a sum rule by which it is expressed in terms of three neutrino mixing angles theta _{12}, theta _{23}, and theta _{13}, and a fixed real angle theta ^nu _{12}, whose value depends on the employed discrete symmetry and its breaking. We consider five underlying symmetry forms of the neutrino mixing matrix: bimaximal (BM), tri-bimaximal (TBM), golden ratio A (GRA) and B (GRB), and hexagonal (HG). For each symmetry form, the sum rule yields specific prediction for cos delta _{mathrm {CP}} for fixed theta _{12}, theta _{23}, and theta _{13}. In the context of the proposed DUNE and T2HK facilities, we study (i) the compatibility of these predictions with present neutrino oscillation data, and (ii) the potential of these experiments to discriminate between various symmetry forms.
Highlights
Introduction and motivationAll compelling neutrino oscillation data are compatible with 3ν mixing [1], i.e., with existence of three light neutrino states ν1,2,3 with definite masses m1,2,3, three orthogonal linear combinations of which form the three flavour neutrino states νe, νμ and ντ
We concentrate on 3ν mixing schemes in which the cosine of the Dirac CP violation phase δCP satisfies a sum rule by which it is expressed in terms of three neutrino mixing angles θ12, θ23, and θ13, and a fixed real angle θ1ν2, whose value depends on the employed discrete symmetry and its breaking
In the present work, using the potential of the future long-baseline (LBL) neutrino oscillation experiments,3 namely, Deep Underground Neutrino Experiment (DUNE) and Tokai to Hyper-Kamiokande (T2HK), we study in detail (i) to what degree the sum rule predictions for cos δCP are compatible with the present neutrino oscillation data, and (ii) how well the considered symmetry forms, BM, TBM, golden ratio A (GRA), golden ratio type B (GRB), and HG, can be discriminated from each other
Summary
All compelling neutrino oscillation data are compatible with 3ν mixing [1], i.e., with existence of three light neutrino states ν1,2,3 with definite masses m1,2,3, three orthogonal linear combinations of which form the three flavour neutrino states νe, νμ and ντ. In the case of the BM symmetry form, the obtained best fit value of cos δCP = −1.26 is unphysical This reflects the fact that the BM symmetry form does not provide a good description of the present best fit values of the neutrino mixing angles, as discussed in [13]. In the present work, using the potential of the future long-baseline (LBL) neutrino oscillation experiments, namely, Deep Underground Neutrino Experiment (DUNE) and Tokai to Hyper-Kamiokande (T2HK), we study in detail (i) to what degree the sum rule predictions for cos δCP are compatible with the present neutrino oscillation data, and (ii) how well the considered symmetry forms, BM, TBM, GRA, GRB, and HG, can be discriminated from each other. In Appendix C, we study the compatibility of the considered symmetry forms with any potentially true values of sin θ23 and δCP in the context of DUNE and T2HK
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