2018/01/09 by Anjan S. Joshipura, Joshipura, Anjan S.
Engineering · Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Neutrino Physics Research #Particle accelerators and beam dynamics #Superconducting Materials and Applications
paper · pdf · doi:10.48550/arxiv.1801.02843
openalex publication_date 2018/01/09 · openalex created_date 2024/04/11 · openalex updated_date 2026/07/28
It is known that the imposition of a class of residual Z2× Z2 symmetries on the neutrino mass matrix Mν and a residual symmetry Zn (n≥ 3) on the Hermitian combination MlMl^† of the charged lepton mass matrix leads to a universal prediction of vanishing Dirac CP phase δ if these symmetries are embedded in Δ(6 n2) groups and if the leptonic doublets transform as a 3 dimensional irreducible representation of the group. The Majorana phases remain arbitrary but they can also be determined in Δ(6 n2) by imposing generalized CP symmetry (GenCP) consistent with the Δ(6 n2) group. We investigate the effects of adding general perturbations on these predictions assuming that perturbations break the Z2× Z2 symmetry completely but preserve GenCP. It is found that if the residual symmetries predict the tri-bimaximal mixing (TBM) among leptons and specific CP conserving values for the Majorana phases then addition of the above perturbations always lead to a neutrino mass matrix invariant under the μ-τ reflection symmetry in the flavour basis with the result that perturbations turn the vanishing δ into maximal value ± \fracπ2. One gets non-vanishing but generally large δ if the predicted zeroeth order mixing deviates from TBM and/or the predicted Majorana phases are non-trivial. We systematically investigate effects of perturbations in such situations and work out the predicted δ for four of the lowest Δ(6 n2) groups with n=2,4,6,8.