Extended scaling and residual flavor symmetry in the neutrino Majorana mass matrix

Abstract

The residual symmetry approach, along with a complex extension for some flavor invariance, is a powerful tool to uncover the flavor structure of the 3 × 3 neutrino Majorana mass matrix M ν toward gaining insights into neutrino mixing. We utilize this to propose a complex extension of the real scaling ansatz for M ν which was introduced some years ago. Unlike the latter, our proposal allows a nonzero mass for each of the three light neutrinos as well as a nonvanishing θ 13 . The generation of light neutrino masses via the type-I seesaw mechanism is also demonstrated. A major result of this scheme is that leptonic Dirac CP-violation must be maximal while atmospheric neutrino mixing does not need to be exactly maximal. Moreover, each of the two allowed Majorana phases, to be probed by the search for nuclear 0νββ decay, has to be at one of its two CP-conserving values. There are other interesting consequences such as the allowed occurrence of a normal mass ordering which is not favored by the real scaling ansatz. Our predictions will be tested in ongoing and future neutrino oscillation experiments at T2K, NOνA and DUNE.

Consequences of minimal seesaw with complex μτ antisymmetry of neutrinos

“…This is what we aim to do in this paper by proposing a complex (CP) extension of µτ flavor antisymmetry CP µτ A and working out its various phenomenological implications. Complex extensions of µτ symmetry [32][33][34] and scaling symmetry [46][47][48] as well as their consequences have been worked out earlier. That is the direction of our thrust here for µτ antisymmetry.…”

“…Nevertheless, a small breaking of the symmetry [93], or somewhat a more moderate version of the symmetry such as the scaling ansatz [46][47][48] will cause a deviation fromm µ =m τ cf. (6.16) and will imply a nonvanishing Y B .…”

Flavoured leptogenesis and CPμτ symmetry

“…To make CP µτ more predictive, a sizable body of work exists to combine flavour symmetries with CP symmetries, despite this being a non-trivial task [23,24]. Several aspects of CP µτ and its alternative versions have also been explored [45][46][47][48][49][50][51][52][53][54].…”

A Froggatt–Nielsen flavor model for neutrino physics

“…As a consequence of being an SRS model, it indeed exhibits an unacceptable vanishing third neutrino mixing angle. The generalization to the model described in this paper eliminates this phenomenological prediction (while keeping a massless neutrino), and puts the new model outside the SRS class [11][12][13][14][15][16][17][18][19].…”