Neutrino masses and mixings with an S3 family permutation symmetry (original) (raw)

Physical Review D, 2010

We explore the consequences of assuming that the neutrino mass matrix is a linear combination of the matrices of a three dimensional representation of the group S_3S_3S_3 and that it has one zero mass eigenvalue. When implemented, these two assumptions allow us to express the transformation matrix relating the mass eigenstates to the flavor eigenstates in terms of a single parameter which we fit to the available data.

Broken S 3 symmetry in the neutrino mass matrix

Physics Letters B, 2011

We explore the feasibility of the discrete flavor symmetry S3S3 to explain the pattern of neutrino masses and mixings. In the flavor basis, the neutrino mass matrix is taken to be invariant under S3S3 symmetry at the zeroth order. The effects of breaking S3S3 symmetry by matrices invariant under different S2S2 subgroups of S3S3 are studied. The resulting retrocirculant perturbation matrix leads to the perturbed S3S3 neutrino mass matrix having a trimaximal eigenvector as suggested by the solar neutrino data. It is found that after the third order perturbation the neutrino mixings only depend on the perturbation parameter and are consistent with the current experimental data leading to very small deviations from tribimaximal mixing. These perturbations in the S3S3 invariant neutrino mass matrix result in interesting interplay between the solar and the reactor neutrino mixing angles. We also get a strongly suppressed range of effective Majorana mass which lies well within the reach of...

The S 3 flavour symmetry: Neutrino masses and mixings

Fortschritte der Physik, 2013

In this work, we discuss the neutrino masses and mixings as the realization of an S 3 flavour permutational symmetry in two models, namely the Standard Model and an extension of the Standard Model with three Higgs doublets. In the S 3 Standard Model, mass matrices of the same generic form are obtained for the neutrinos and charged leptons when the S 3 flavour symmetry is broken sequentially according to the chain S 3L ⊗ S 3R ⊃ S diag 3 ⊃ S 2 . In the minimal S 3 -symmetric extension of the Standard Model, the S 3 symmetry is left unbroken, and the concept of flavour is extended to the Higgs sector by introducing in the theory three Higgs fields which are SU (2) doublets. In both models, the mass matrices of the neutrino and charged leptons are reparametrized in terms of their eigenvalues, and exact, explicit analytical expressions for the neutrino mixing angles as functions of the masses of neutrinos and charged leptons are obtained. In the case of the S 3 Standard Model, from a χ 2 fit of the theoretical expressions of the lepton mixing matrix to the values extracted from experiment, the numerical values of the neutrino mixing angles are obtained in excellent agreement with experimental data. In the S 3 extension of the Standard Model, if two of the right handed neutrinos masses are degenerate, the reactor and atmospheric mixing angles are determined by the masses of the charged leptons, yielding θ 23 in excellent agreement with experimental data, and θ 13 different from zero but very small. If the masses of the three right handed neutrinos are assumed to be different, then it is possible to get θ 13 also in very good agreement with experimental data. We also show the branching ratios of some selected flavour changing neutral currents (FCNC) process as well as the contribution of the exchange of a neutral flavour changing scalar to the anomaly of the magnetic moment of the muon.

Family Symmetry and Neutrino Bi-Tri-Maximal Mixing

Nuclear Physics B, 2006

The observed large mixing angles in the lepton sector may be the first signal for the presence of a non-Abelian family symmetry. However, to obtain the significant differences between the mixing of the neutrino and charged fermion sectors, the vacuum expectation values involved in the breaking of such a symmetry in the two sectors must be misaligned. We investigate how this can be achieved in models with an SU (3) f family symmetry consistent with an underlying GUT. We show that such misalignment can be achieved naturally via the seesaw mechanism. We construct a specific example in which the vacuum (mis)alignment is guaranteed by additional symmetries. This model generates a fermion mass structure consistent with all quark and lepton masses and mixing angles. Neutrino mixing is close to bi-tri-maximal mixing.

Family Symmetry and Neutrino Mixing

Physical Review Letters, 1998

The observed quark hierarchies suggest a simple family symmetry. Generalized to leptons through grand-unified quantum numbers, it produces a neutrino mixing matrix with order-one ν µ − ν τ mixing, and order-λ 3 ν e − ν µ and ν e − ν τ mixings. The intrafamily hierarchy and observed neutrino mass differences together require this symmetry to be anomalous, suggesting through the Green-Schwarz mechanism a string or M-theory origin for the symmetry.

Relating neutrino masses and mixings by discrete symmetries

Physical Review D, 2013

Lepton mixing can originate from the breaking of a flavor symmetry in different ways in the neutrino and the charged lepton sector. We propose an extension of this framework which allows to connect the mixing parameters with masses, and more precisely, with certain types of degeneracy of the neutrino mass spectrum. We obtain relations between the mixing parameters for the cases of partial degeneracy, m 1 = m 2 , and complete degeneracy, m 1 = m 2 = m 3. These relations determine also the Majorana phases. It is shown that relatively small corrections to these lowest order results can produce the required mass splitting and modify the mixing without significant changes of the other symmetry results.

Broken S3 symmetry in the neutrino mass matrix and non-zero θ13

Physics Letters B, 2012

We study the effects of breaking S 3 symmetry in the neutrino mass matrix for the masses and mixing matrix of neutrinos. At zeroth order the model gives degenerate neutrino masses and accommodates tribimaximal mixing. We introduce perturbations in terms of a small and complex parameter. The perturbations are introduced in a manner such that the S 3 symmetry is broken by its elements in the same representation. Successive perturbations introduce mass splitting, sizable non-zero reactor mixing angle and CP violation. This scheme of breaking S 3 symmetry can reproduce a relatively large reactor mixing angle as suggested by the recent T2K results. The effective neutrino mass is predicted to be large which is testable in the ongoing and forthcoming neutrinoless double beta decay experiments.

Almost Maximally Broken Permutation Symmetry for Neutrino Mass Matrix

Modern Physics Letters A, 1997

Assuming three light neutrinos are Majorana particles, we propose mass matrix ansatz for the charged leptons and Majorana neutrinos with family symmetry S3 broken into S1 and S2, respectively. Each matrix has three parameters, which are fixed by measured charged lepton masses, differences of squared neutrino masses relevant to the solar and the atmospheric neutrino puzzles, and the masses of three light Majorana neutrinos as a candidate for hot dark matter with ∑|mν|~ 6 eV . The resulting neutrino mixing is compatible with the data for the current upper limit, th <0.7 eV , of neutrino-less double beta decay experiments, and the current data for various types of neutrino oscillation experiments. One solution of our model predicts that νμ→ντ oscillation probability is about < 0.008 with Δm2 ~ 10-2 eV 2, which may not be accessible at CHORUS and other on-going experiments.