Almost general analysis of μ − τ reflection symmetry perturbed by charged leptons and its testability by DUNE and T2HK

In this paper, we generally analyze the μ − τ reflection symmetry modified by small mixings of charged leptons and how will future experiments verify deviations from the predictions of the symmetry. As an approximation, the left-handed diagonalization U e of charged leptons is assumed to have a similar magnitude as the CKM matrix. In other words, the 1-3 mixing is neglected and the 1-2 and 2-3 mixing are to be approximately O ( 0.1 ) . The Dirac CP phase δ of the MNS matrix is evaluated in such parameter regions. As a result, deviations from the predictions sin ⁡ θ 23 = π / 4 and δ = ± π / 2 depend on relative CP phases between U e and diagonalization of neutrinos U ν . While phases of the second and third generations cause only about ± 10 ∘ deviations for the Dirac phase δ , the phase of the first generation can cause up to ± 30 ∘ . This flavor dependence is distinguished to some extent by the next-generation experiments. On the other hand, if δ is not observed, such a scenario is excluded by about 5 years of observation.