Tri‐bimaximal neutrino mixing and discrete flavour symmetries

Abstract:The recent results that θ 13 is relatively large, of the order of the previous upper bound, and the indications of a sizable deviation of θ 23 from the maximal value are in agreement with the predictions of Anarchy in the lepton sector. The quark and charged lepton hierarchies can then be reproduced in a SU(5) GUT context by attributing nonvanishing U(1) FN charges, different for each family, only to the SU(5) tenplet states. The fact that the observed mass hierarchies are stronger for up quarks than for down quarks and charged leptons supports this idea. As discussed in the past, in the flexible context of SU(5) ⊗ U(1) FN , different patterns of charges can be adopted going from Anarchy to various types of hierarchy. We revisit this approach by also considering new models and we compare all versions to the present data. As a result we confirm that, by relaxing the ansatz of equal U(1) FN charges for all SU(5) pentaplets and singlets, better agreement with the data than for Anarchy is obtained without increasing the model complexity. We also present the distributions obtained in the different models for the Dirac CP-violating phase. Finally we discuss the relative merits of these simple models.

Section: Jhep11(2012)139mentioning

confidence: 99%

Repressing anarchy in neutrino mass textures

Altarelli

Feruglio

Masina

et al. 2012

“…The first class of theories exhibited very predictive mass textures [8][9][10][11][12][13][14][15][16][16][17][18][19][20][21][22][23][24][25] and provided a certain protection from flavour violating processes [26][27][28][29][30][31][32][33][34]. However, the 2011 discovery of a nonvanishing, and relatively large, leptonic reactor angle [35][36][37][38][39] has raised strong doubts on the use of non-Abelian discrete models, whose most common prediction was a vanishing reactor angle.…”

Section: Introductionmentioning

confidence: 99%

The minimal flavour violating axion

Arias-Aragón

Merlo

2017

Self Cite

The solution to the Strong CP problem is analysed within the Minimal Flavour Violation (MFV) context. An Abelian factor of the complete flavour symmetry of the fermionic kinetic terms may play the role of the Peccei-Quinn symmetry in traditional axion models. Its spontaneous breaking, due to the addition of a complex scalar field to the Standard Model scalar spectrum, generates the MFV axion, which may redefine away the QCD theta parameter. It differs from the traditional QCD axion for its couplings that are governed by the fermion charges under the axial Abelian symmetry. It is also distinct from the so-called Axiflavon, as the MFV axion does not describe flavour violation, while it does induce flavour non-universality effects. The MFV axion phenomenology is discussed considering astrophysical, collider and flavour data.

“…The use of antisymmetry is found to be more predictive than symmetry. It is able to restrict both neutrino masses and mixing angles unlike all the previous works in this category which [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] could predict only mixing angles. Moreover, the antisymmetry condition by itself is sufficient for determining all possible discrete residual antisymmetry operators S ν residing in SU(3).…”

Section: Jhep11(2015)186mentioning

confidence: 99%

Neutrino masses and mixing from flavour antisymmetry

Joshipura¹

2015

We discuss consequences of assuming (i) that the (Majorana) neutrino mass matrix M ν displays flavour antisymmetry, S T ν M ν S ν = −M ν with respect to some discrete symmetry S ν contained in SU(3) and (ii) S ν together with a symmetry T l of the Hermitian combination M l M † l of the charged lepton mass matrix forms a finite discrete subgroup G f of SU(3) whose breaking generates these symmetries. Assumption (i) leads to at least one massless neutrino and allows only four textures for the neutrino mass matrix in a basis with a diagonal S ν if it is assumed that the other two neutrinos are massive. Two of these textures contain a degenerate pair of neutrinos. Assumption (ii) can be used to determine the neutrino mixing patterns. We work out these patterns for two major group series ∆(3N 2 ) and ∆(6N 2 ) as G f . It is found that all ∆(6N 2 ) and ∆(3N 2 ) groups with even N contain some elements which can provide appropriate S ν . Mixing patterns can be determined analytically for these groups and it is found that only one of the four allowed neutrino mass textures is consistent with the observed values of the mixing angles θ 13 and θ 23 . This texture corresponds to one massless and a degenerate pair of neutrinos which can provide the solar pair in the presence of some perturbations. The well-known groups A 4 and S 4 provide examples of the groups in respective series allowing correct θ 13 and θ 23 . An explicit example based on A 4 and displaying a massless and two quasi degenerate neutrinos is discussed.