Residual Symmetries Applied to Neutrino Oscillations at NO$\hat{I}½$A and T2K

Abstract

The results previously obtained from the model-independent application of a generalized hidden horizontal ${\mathbb{Z}}_2$ symmetry to the neutrino mass matrix are updated using the latest global fits for the neutrino oscillation parameters. The resulting prediction for the Dirac $CP$ phase $\hat{I}{´}_D$ is in agreement with recent results from T2K. The distribution for the Jarlskog invariant $J_{\hat{I}}½$ has become sharper and appears to be approaching a particular region. The approximate effects of matter on long baseline neutrino experiments are explored, and it is shown how the weak interactions between the neutrinos and the particles that make up the Earth can help to determine the mass hierarchy. A similar strategy is employed to show how NO$\hat{I}½$A and T2K could determine the octant of $\hat{I}{¸}_a(\equiv \hat{I}{¸}_{23})$. Finally, the exact effects of matter are obtained numerically in order to make comparisons with the form of the approximate solutions. From this analysis there emerges some interesting features of the effective mass eigenvalues.

9 pages, 1 table, 17 figures