Can an unbroken flavour symmetry provide an approximate description of lepton masses and mixing?

Reyimuaji, Yakefu; Romanino, Andrea

doi:10.1007/jhep03(2018)067

Cited by 17 publications

(28 citation statements)

References 49 publications

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“…This possibility has been investigated in ref. [118] for arbitrary flavour symmetry groups. In particular, this analysis directly applies to the case of the flavour symmetry being a residual modular symmetry.…”

Section: Jhep04(2021)206mentioning

confidence: 99%

Fermion mass hierarchies, large lepton mixing and residual modular symmetries

Novichkov

Penedo

Petcov

2021

J. High Energ. Phys.

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In modular-invariant models of flavour, hierarchical fermion mass matrices may arise solely due to the proximity of the modulus τ to a point of residual symmetry. This mechanism does not require flavon fields, and modular weights are not analogous to Froggatt-Nielsen charges. Instead, we show that hierarchies depend on the decomposition of field representations under the residual symmetry group. We systematically go through the possible fermion field representation choices which may yield hierarchical structures in the vicinity of symmetric points, for the four smallest finite modular groups, isomorphic to S3, A4, S4, and A5, as well as for their double covers. We find a restricted set of pairs of representations for which the discussed mechanism may produce viable fermion (charged-lepton and quark) mass hierarchies. We present two lepton flavour models in which the charged-lepton mass hierarchies are naturally obtained, while lepton mixing is somewhat fine-tuned. After formulating the conditions for obtaining a viable lepton mixing matrix in the symmetric limit, we construct a model in which both the charged-lepton and neutrino sectors are free from fine-tuning.

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Section: Jhep04(2021)206mentioning

confidence: 99%

Fermion mass hierarchies, large lepton mixing and residual modular symmetries

Novichkov

Penedo

Petcov

2021

J. High Energ. Phys.

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“…We now illustrate the results of the analysis. The details and full proofs can be found in [20]. First of all, it turns out that the pattern of lepton masses and mixings only depends on the dimension, type (real, pseudoreal, complex), and equivalence of the irreducible components of the representations U l , U e c .…”

Section: Pos(corfu2017)024mentioning

confidence: 99%

General considerations on lepton mass matrices

Romanino¹,

Reyimuaji²

2018

Proceedings of Corfu Summer Institute 2017 "Schools and Workshops on Elementary Particle Physics and Gravity" — PoS(CORFU2017)

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We classify the flavour groups and representations providing, in the symmetric limit, an approximate description of lepton masses and mixings. We assume that the light neutrinos are of Majorana type and that the flavour symmetry directly constrains their mass matrix. The representations can be characterised by the dimension, type (real, pseudoreal, complex), and equivalence of its irreducible components, and in terms of such a classification we find only six viable cases. It turns out that the neutrinos are always either anarchical or have an inverted hierarchical spectrum. Therefore, if the hint of a normal hierarchical spectrum were confirmed, we would conclude (under the above assumption) that symmetry breaking effects must play a primary role in the understanding of neutrino flavour observables.

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“…However, because of the exceedingly small value of neutrino masses, it is conceivable that the whole structure of the neutrino sector might depend solely on symmetry-breaking effects, in which case it would be hard to identify a flavour symmetry, even when accurate determinations of all the relevant parameters (neutrino masses, mixing, and CP violating phases) will be available. 1 1 The opposite situation in which the symmetric limit provides a good approximation to the structure of the neutrino mass matrix has been recently thoroughly analysed in [23].…”

Section: Introductionmentioning

confidence: 99%

Covert symmetries in the neutrino mass matrix

Björkeroth

Luzio

Mescia

et al. 2020

J. High Energ. Phys.

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The flavour neutrino puzzle is often addressed by considering neutrino mass matrices m with a certain number of vanishing entries (m ij = 0 for some values of the indices), since a reduction in the number of free parameters increases the predictive power. Symmetries that can enforce textures zero can also enforce a more general type of conditions f (m ij ) = 0 with f some function of the matrix elements m ij . In this case m can have all entries non-vanishing with no reduction in its predictive power. We classify all generationdependent U (1) symmetries which, in the presence of two leptonic Higgs doublets, can reduce the number of independent high-energy parameters of type-I seesaw to the minimum number compatible with non-vanishing neutrino mixings and CP violation. These symmetries are broken above the scale where the effective operator is generated and can thus remain covert, in the sense that no explicit evidence of the symmetry can be read off the neutrino mass matrix, and different symmetries can give rise to the same low-energy structure. We find that only two cases are viable: one yields a structure with two zerotextures already considered in the literature, the other has no zero-textures and has never been considered before. It predicts normal ordering, a lightest neutrino mass ∼ 10 meV, a Dirac phase δ ∼ 3π 2 and definite values for the Majorana phases.

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Can an unbroken flavour symmetry provide an approximate description of lepton masses and mixing?

Cited by 17 publications

References 49 publications

Fermion mass hierarchies, large lepton mixing and residual modular symmetries

Fermion mass hierarchies, large lepton mixing and residual modular symmetries

General considerations on lepton mass matrices

Covert symmetries in the neutrino mass matrix

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