Exploring partial μ-τ Reflection symmetry at DUNE and Hyper-Kamiokande

We study the origin, consequences, and testability of a hypothesis of "partial μ-τ" reflection symmetry. This symmetry predicts |Uμi|=|Uτi|(i=1,2,3) for a single column of the leptonic mixing matrix U. Depending on whether this symmetry holds for the first or second column of U, different correlations between θ23 and δCP can be obtained. This symmetry can be obtained using discrete flavor symmetries. In particular, all of the subgroups of SU(3) with three-dimensional irreducible representation, which are classified as class C or D, can lead to partial μ-τ reflection symmetry. We show how the predictions of this symmetry compares with the allowed area in the sin2θ23-δCP plane as obtained from the global analysis of neutrino oscillation data. Furthermore, we study the possibility of testing these symmetries at the proposed DUNE and Hyper-Kamiokande (HK) experiments (T2HK, T2HKK), by incorporating the correlations between θ23 and δCP that are predicted by the symmetries. We find that when the simulated data of DUNE and HK are fitted with the symmetry predictions, the θ23-δCP parameter space gets largely restricted near the charge parity conserving values of δCP. Finally, we illustrate the capability of these experiments to distinguish between the two cases leading to partial μ-τ symmetry, namely |Uμ1|=|Uτ1| and |Uμ2|=|Uτ2|.