Leptonic CP violation in flipped SU(5) GUT from $Z_{12-I}$ Orbifold Compactification

Abstract We obtain a phenomenologically acceptable PMNS matrix in a flipped SU(5) model, possessing the Z 4 R discrete symmetry, from the compactification of heterotic string E 8 × E 8 ′ . To analyze the Jarlskog determinant efficiently, we include the simple Kim-Seo form for the Pontecorbo-Maki-Nakagawa-Sakata matrix. We also noted that | δ PMNS | ≲ 63 o for the normal hierarchy of neutrino masses with the PDG book parametrization.