Direct and semi-direct approaches to lepton mixing with a massless neutrino

Stephen F. King, Patrick Otto Ludl
2016 Journal of High Energy Physics  
We discuss the possibility of enforcing a massless Majorana neutrino in the direct and semi-direct approaches to lepton mixing, in which the PMNS matrix is partly predicted by subgroups of a discrete family symmetry, extending previous group searches up to order 1535. We find a phenomenologically viable scheme for the semi-direct approach based on Q(648) which contains Δ(27) and the quaternion group as subgroups. This leads to novel predictions for the first column of the PMNS matrix
more » ... ng to a normal neutrino mass hierarchy with m_1=0, and sum rules for the mixing angles and phase which are characterised by the solar angle being on the low side θ_12∼ 31^∘ and the Dirac (oscillation) CP phase δ being either about ± 45^∘ or ±π.
doi:10.1007/jhep06(2016)147 fatcat:ytipuyko3jg73e5llch4crvyze