CP violation in neutrino mixing with δ=−π/2δ=−π/2 in A4A4 Type-II seesaw model

We study a class of models for neutrino mass matrix in Type-II seesaw with A4A4 family symmetry. The resulting neutrino mass matrix can be naturally made to respect a μ–τμ–τ exchange plus CP conjugate symmetry (GLS) with the CP violating phase δ   and the mixing angle θ23θ23 predicted to be ±π/2±π/2 and π/4π/4, respectively. When GLS is explicitly broken by complex Yukawa couplings, the model predictions for δ   and θ23θ23 can be significantly modified. Should future experiments indeed determine θ23θ23 and δCPδCP away from the GLS limit values, one then had to consider models with broken GLS. We study several simple scenarios to show how the modifications arise w̱hen GLS is broken and how future experiments can test this class of models.