Symmetries and generalisations of tri-bimaximal neutrino mixing

Abstract:We perform a detailed analysis of ∆(6n 2 ) family symmetry combined with a generalised CP symmetry in the lepton sector, breaking to different remnant symmetries G ν in the neutrino and G l in the charged lepton sector, together with different remnant CP symmetries in each sector. We discuss the resulting mass and mixing predictions for G ν = Z 2 with G l = K 4 , Z p , p > 2 and G ν = K 4 with G l = Z 2 . All cases correspond to the preserved symmetry smaller than the full Klein symmetry, as in the semi-direct approach, leading to predictions which depend on a single undetermined real parameter, which mainly determines the reactor angle. We focus on five phenomenologically allowed cases for which we present the resulting predictions for the PMNS parameters as a function of n, as well as the predictions for neutrinoless double beta decay.

Section: Jhep12(2014)007mentioning

confidence: 99%

Generalised CP and Δ(6n 2) family symmetry in semi-direct models of leptons

Ding

King

Neder

2014

“…By now we have a rather precise knowledge of the leptonic mixing angles [1][2][3][4][5][6][7][8][9] which, within the experimental accuracy, are consistent with the Tri-Bimaximal (TB) pattern [10][11][12][13][14][15][16] and, as such, are very different from the quark mixing angles. A still open and challenging problem is that of formulating a natural model of Grand Unification based on SO(10), leading not only to a good description of quark masses and mixing but also, in addition, of charged lepton masses and to approximate TB neutrino mixing.…”

Section: Introductionmentioning

confidence: 99%

Different SO(10) paths to fermion masses and mixings

Altarelli

Blankenburg

2011

137

Recently SO(10) models with type-II see-saw dominance have been proposed as a promising framework for obtaining Grand Unification theories with approximate Tribimaximal (TB) mixing in the neutrino sector. We make a general study of SO(10) models with type-II see-saw dominance and show that an excellent fit can be obtained for fermion masses and mixings, also including the neutrino sector. To make this statement more significant we compare the performance of type-II see-saw dominance models in fitting the fermion masses and mixings with more conventional models which have no built-in TB mixing in the neutrino sector. For a fair comparison the same input data and fitting procedure is adopted for all different theories. We find that the type-II dominance models lead to an excellent fit, comparable with the best among the available models, but the tight structure of this framework implies a significantly larger amount of fine tuning with respect to other approaches.

“…(2.11) and m H + a = m φa for the EWPOs, we find that the modified branching ratio of muonic τ decay is at most, 6) including the contribution of µ mass. Br(τ → µνν) SM is the SM prediction and this modified value is within the error of the current experimental measurement of the τ decay [69].…”

Section: Jhep10(2015)042mentioning

confidence: 71%

“…We can expect that (e, µ) and (e, τ ) elements may be enhanced because of the sizable Yukawa couplings, as we have seen in the µ → eγ and τ → eγ processes. Assuming (δm 2 H ) 22 is only nonzero among the T -breaking terms, we find that y 1 eµ is approximately estimated as, 6) where the dependence of H 1 and H q in (δm 2 H ) 22 is ignored. Eventually y 1 eµ is very tiny, because of the stringent µ → eγ constraint.…”

Section: Mass Mixing Induced By T -Breaking Termsmentioning

confidence: 91%

“…This BSM would be very attractive and reasonable, and so many types of flavor symmetric models have been proposed so far [2][3][4]. Especially, we could find so many models motivated by the large mixing in neutrino sector, because the experimental result may imply so-called Tri-Bi maximal mixing [5][6][7], which can be easily accommodated by the BSMs with non-Abelian discrete flavor symmetry such as A 4 [8][9][10][11][12], S 4 [13][14][15], and ∆ (27) [16] etc.. Recent result on the nonzero θ 13 [17][18][19][20][21][22] may require some small modifications in those models, but we could expect that so many kinds of flavor symmetric models can be still consistent with the experimental results [4,.…”

Section: Jhep10(2015)042mentioning

confidence: 99%

See 1 more Smart Citation

Study of lepton flavor violation in flavor symmetric models for lepton sector

Kobayashi

Omura

Takayama

et al. 2015

Flavor symmetric model is one of the attractive Beyond Standard Models (BSMs) to reveal the flavor structure of the Standard Model (SM). A lot of efforts have been put into the model building and we find many kinds of flavor symmetries and setups are able to explain the observed fermion mass matrices. In this paper, we look for common predictions of physical observables among the ones in flavor symmetric models, and try to understand how to test flavor symmetry in experiments. Especially, we focus on the BSMs for leptons with extra Higgs SU(2) L doublets charged under flavor symmetry. In many flavor models for leptons, remnant symmetry is partially respected after the flavor symmetry breaking, and it controls well the Flavor Changing Neutral Currents (FCNCs) and suggests some crucial predictions against the flavor changing process, although the remnant symmetry is not respected in the full lagrangian. In fact, we see that τ − → e + µ − µ − (µ + e − e − ) and e + e − → τ + τ − (µ − µ + ) processes are the most important in the flavor models that the extra Higgs doublets belong to triplet representation of flavor symmetry. For instance, the stringent constraint from the µ → eγ process could be evaded according to the partial remnant symmetry. We also investigate the breaking effect of the remnant symmetry mediated by the Higgs scalars, and investigate the constraints from the flavor physics: the flavor violating τ and µ decays, the electric dipole moments, and the muon anomalous magnetic moment. We also discuss the correlation between FCNCs and nonzero θ 13 , and point out the physical observables in the charged lepton sector to test the BSMs for the neutrino mixing.