Charged Lepton Mass Research Articles

Phenomenology of 3-3-1 models with a radiative inverse seesaw mechanism

We propose two models based on the SU(3)C×SU(3)L×U(1)X gauge symmetry, each incorporating distinct inverse seesaw mechanisms for generating neutrino masses at the radiative level. Therefore, neutrino masses are suppressed by the radiative nature of the mass generation mechanism, which occurs after the spontaneous breaking of the global lepton number symmetry. Both scenarios discussed here are characterized by the presence of vectorlike charged leptons, which are involved in generating the masses of the Standard Model charged leptons. These additional vectorlike fermions also contribute to the anomalous magnetic moments of the muon. We perform a detailed analysis of the scalar sectors, show that these models can successfully accommodate the observed baryon asymmetry through resonant leptogenesis, and compute the rates of charged lepton flavor-violating decays, such as μ→eγ. We discuss the constraints of the model arising from these processes and those associated with the nonunitarity of the lepton mixing matrix. Published by the American Physical Society 2024

Fermion masses and mixings and g − 2 muon anomaly in a Q6 flavored 2HDM

We propose an extended 2HDM with Q6×Z4×Z2 symmetry that can successfully accommodate the SM fermion mass and mixing hierarchy. The tiny masses of the active neutrinos are generated from a type-I seesaw mechanism mediated by very heavy right-handed Majorana neutrinos. The model gives a natural explanation of the charged lepton mass hierarchy. Besides that, the experimental values of the physical observables of the neutrino sector: the neutrino mass squared splittings, the leptonic mixing angles and the leptonic Dirac CP violating phase, are also successfully reproduced for both normal and inverted neutrino mass hierarchies. We find a feasible range of values for the leptonic Dirac CP phase to be in the ranges δCP∈(305.90,348.70)∘ for normal ordering and δCP∈(308.00,348.00)∘ for inverted ordering, which is consistent with the 3σ experimentally allowed limits. The sum of neutrino masses is obtained as ∑mi∈(58.03,60.51) meV for normal ordering and ∑mi∈(98.07,101.40) meV for inverted ordering which are well consistent with all the recent limits. In addition, the obtained ranges for the effective neutrino masses are 〈mee〉∈(3.80,4.38) meV, mβ∈(8.53,9.34)meV for normal ordering and 〈mee〉∈(47.85,49.58) meV, mβ∈(48.39,50.09)meV for inverted ordering which are in agreement with the recent experimental bounds. For the quark sector, the derived results are also in agreement with the recent data on the quark masses and mixing angles. The model under consideration can also accommodate the muon anomalous magnetic moment.

Models of Radiative Linear Seesaw with Electrically Charged Mediators

Abstract We propose two versions of radiative linear seesaw models, where electrically charged scalars and vector-like leptons generate the Dirac neutrino mass submatrix at the one- and two-loop levels. In these models, the Standard Model charged lepton masses are generated from a one-loop-level radiative seesaw mechanism mediated by charged exotic vector-like leptons and electrically neutral scalars running in the loops. These models can successfully accommodate the current amount of dark matter and baryon asymmetries observed in the universe, as well as the muon anomalous magnetic moment.

Flavino dark matter in a non-Abelian discrete flavor model

We study a relic density of the “flavino” dark matter in modified Altarelli and Feruglio A4 model which is respecting the SU(2)L × A4 × Z3 × U(1)R symmetry. We calculate the Lagrangian from the superpotential in the model. In estimating the relic density, we consider the relevant interactions from the Lagrangian that realize the vacuum expectation value alignments and charged lepton masses where we assume that the supersymmetry breaking effects are small for “flavon” sector. As a result, we find the degenerate masses between the lightest “flavon” and “flavino”, and only two parameters in the potential determines the relic density. Then the allowed parameter space of these parameters are estimated from the relic density calculation taking a constraint from lepton flavor violation into account. We also briefly discuss other dark matter physics such as the direct detection, indirect detection, and collider search.

Non-holomorphic modular flavor symmetry

The formalism of non-holomorphic modular flavor symmetry is developed, and the Yukawa couplings are level N polyharmonic Maaß forms satisfying the Laplacian condition. We find that the integer (even) weight polyharmonic Maaß forms of level N can be decomposed into multiplets of the finite modular group ΓN′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Gamma}_N^{\\prime } $$\\end{document} (ΓN). The original modular invariance approach is extended by the presence of negative weight polyharmonic Maaß forms. The non-holomorphic modular flavor symmetry can be consistently combined with the generalized CP symmetry. We present three example models for lepton sector based on the Γ3 ≅ A4 modular symmetry, the charged lepton masses and the neutrino oscillation data can be accommodated very well, and the predictions for the leptonic CP violation phases and the effective Majorana neutrino mass are studied.

A modular SU (5) littlest seesaw

We extend the littlest modular seesaw to a Grand Unified scenario based on SU (5) endowed with three modular S4 symmetries. We leverage symmetry protected zeroes in the leptonic and down quark sectors to suppress deviations to the littlest modular seesaw predictions, but not contributions to the quark mixing. The model is supplemented by two weighton fields, such that the hierarchical nature of the charged-lepton masses, as well as the quark masses and mixing, stem from the content and symmetries of the model, rather than a hierarchical nature of the Yukawa coefficients.

Minimal SU(5) theory on the edge: The importance of being effective

It is well known that the minimal renormalizable SU(5) grand unified theory is ruled out: it predicts the same masses of down quarks and charged leptons, the gauge couplings do not unify, and neutrinos are massless. We show here that all this can be cured simultaneously by the addition of higher-dimensional effective operators. However, the theory lives on the edge since the unification scale turns out as low as roughly 1014 GeV, threatening proton longevity. If the lower bound on the proton lifetime was to be increased by an order of magnitude, the usual desert in energies between the weak and unification scales would be populated. We also revisit two minimal extensions of this theory that offer a dynamical seesaw origin of neutrino mass and discuss the resulting consequences. Published by the American Physical Society 2024

A 3HDM with Z[formula omitted] Z[formula omitted] model for nearly co-bimaximal mixing

We suggest a combination of Z4⋊Z4 symmetry with the B−L gauge model in the framework of three-Higgs-doublet model (3HDM). The co-bimaximal mixing pattern is broken by the charged lepton contribution which can accommodate the global analysis of neutrino oscillation data. The tiny of the light neutrino masses and neutrino mass hierarchy are produced by the type-I seesaw mechanism. The charged-lepton mass hierarchy is naturally achieved and the constraints on the efictive neutrino masses are in good agreement with the recent experimental bounds.

Quark-lepton mass relations from modular flavor symmetry

The so-called Golden Mass Relation provides a testable correlation between charged-lepton and down-type quark masses, that arises in certain flavor models that do not rely on Grand Unification. Such models typically involve broken family symmetries. In this work, we demonstrate that realistic fermion mass relations can emerge naturally in modular invariant models, without relying on ad hoc flavon alignments. We provide a model-independent derivation of a class of mass relations that are experimentally testable. These relations are determined by both the Clebsch-Gordan coefficients of the specific finite modular group and the expansion coefficients of its modular forms, thus offering potential probes of modular invariant models. As a detailed example, we present a set of viable mass relations based on the Γ4 ≅ S4 symmetry, which have calculable deviations from the usual Golden Mass Relation.

Neutrino phenomenology in a model with generalized CP symmetry within type-I seesaw framework

We investigate the consequences of generalized CP (GCP) symmetry within the context of the two Higgs doublet model (2HDM), specifically focusing on the lepton sector. Utilizing the type-I seesaw framework, we study an intriguing connection between the Dirac Yukawa couplings originating from both Higgs fields, leading to a reduction in the number of independent Yukawa couplings and simplifying the scalar and Yukawa sectors when compared to the general 2HDM. The constraints coming from CP symmetry of class three (CP3) results in two right-handed neutrinos having equal masses and leads to a diagonal right-handed Majorana neutrino mass matrix. Notably, CP symmetry experiences a soft breaking due to the phase associated with the vacuum expectation value of the second Higgs doublet. The model aligns well with observed charged lepton masses and neutrino oscillation data, explaining both masses and mixing angles, and yields distinct predictions for normal and inverted neutrino mass hierarchies. It features a novel interplay between atmospheric mixing angle θ23 and neutrino mass hierarchy: The angle θ23 is below maximal for the normal hierarchy and above maximal for inverted hierarchy. Another interesting feature of the model is inherent CP violation for the inverted hierarchy. Published by the American Physical Society 2024

Asymmetrical braneworlds and the charged lepton mass spectrum

A braneworld mechanism for explaining the mass spectrum of the charged leptons is proposed. Based on the existence of an asymmetric warp factor for a 5+1-dim braneworld scenario, the proper fractions between the masses of the electron, muon and tauon are achieved. As a straightforward consequence, our results coincide with the Koide's mass formula.

Tri-Bi-Maximal flavor pattern deviation using equivalent class

We assume that the neutrino mass matrix Mν, in the model-independent context, is diagonalized by the Tri-Bi-Maximal (TBM) pattern. In the following, we explore the TBM mixing pattern deviation by considering different textures for the charged lepton matrix, which are classified into equivalence classes that allow us to reproduce the experimental data on neutrino oscillation. Our target is on the charged lepton matrix with the minimum number of free parameters, i.e., the maximum number of zeros of the texture that allows us to correctly reproduce the value of the reactor mixing angle θ13. We show a deviation from the TBM pattern in terms of the charged leptonic masses, which provides a prediction value for the phase factors in the charged lepton mass matrices. These are related to the “Dirac-like” CP and “Majorana-like” phase factors. For the last type of phase, we show its phenomenological implications through effective Majorana mass in the neutrinoless double-beta decay.

LFV Higgs and Z-boson decays: leptonic CPV phases and CP asymmetries

Heavy neutral leptons are motivated by several extensions of the Standard Model and their presence induces modifications in the lepton mixing matrix, including new Dirac and Majorana CP violating phases. It has been recently shown that these phases play an important role in lepton number and lepton flavour violating decays and transitions, with a striking impact for the predicted rates of certain observables. In this work, we now consider the potential role of the heavy neutral fermions and of the new CP violating phases in Higgs and Z-boson lepton flavour violating decays H,Zrightarrow ell _alpha ^pm ell _beta ^mp , as well as in the corresponding CP asymmetries. In order to allow for a thorough analysis, we derive the full analytical expressions of the latter observables, taking into account the effect of the (final state) charged lepton masses. A comprehensive exploration of lepton flavour violating Z and Higgs decays confirms that these are very sensitive to the presence of the additional heavy neutral leptons. Moreover, the new CPV phases have a clear impact on the decay rates, leading to both destructive and constructive interferences. Interestingly, in the mu tau sector, the Zrightarrow ell _alpha ^pm ell _beta ^mp rates are within reach of FCC-ee, with associated CP asymmetries that can potentially reach up to 20–30%.

Non-SUSY lepton flavor model with the three Higgs doublet model

Abstract We propose a simple non-supersymmetric lepton flavor model with A4 symmetry. The A4 group is a minimal one that includes triplet irreducible representation. We introduce three Higgs doublets, which are assigned as a triplet of the A4 symmetry. It is natural that there are three generations of the Higgs fields, as with the standard model fermions. We analyze the potential and find the vacuum expectation values for the local minimum. In the vacuum expectation values, we obtain the charged lepton, Dirac neutrino, and right-handed Majorana neutrino mass matrices. By using the type-I seesaw mechanism, we get the left-handed Majorana neutrino mass matrix. In the NuFIT 5.1 data, we predict the Dirac CP phase and the Majorana phases for the only inverted neutrino mass hierarchy. In particular, the Dirac CP phase and lepton mixing angle θ23 are strongly correlated. If θ23 is more precisely measured, the Dirac CP phase is more precisely predicted, and vice versa. We also predict the effective mass for neutrinoless double beta decay mee ≃ 47.1 [meV] and the lightest neutrino mass m3 ≃ 0.789–1.43 [meV]. This will be testable with our model in near-future neutrino experiments.

Neutrino mixing matrix and masses from a particular two-zero texture based on A 4 symmetry

The current study aims to investigate the particular case of two zeros in a Majorana neutrino mass matrix based on A 4 symmetry, where charged lepton mass matrix is diagonal. The texture is with (μ, μ) and (τ, τ) vanishing element of the neutrino mass matrix. The texture has magic and μ − τ symmetry, with a tribimaximal form of the mixing matrix, which leads to θ 13 = 0 that it is not consistent with experimental data and at first, does not seem to be allowed. Since θ 13 a small mixing angle compared to others neutrino mixing angles justifies the use of perturbation theory. We propose that, θ 13, and the Dirac phase δ, and two Majorana phases ρ and σ could be generated by using a complex symmetric perturbation mass matrix in the mass basis and find that affect to the atmospheric mixing angle. We show that only the predictions of the case I, with Δ < 0 and , are consistent with the experimental data. Furthermore, the allowed range of our parameter space and complex elements of perturbation mass matrix are found, which led to finding the allowed region of the neutrino masses, the Majorana phases, the effective neutrino mass for the neutrinoless double beta decay, the allowed deviation of θ 23 from 45°, and to predict the normal neutrino mass hierarchy. The predicted region of and θ 23 are in line with the current experimental data which indicate the accuracy of our model and its results. The results of the case II, with Δ > 0 and , are ruled out.

Texture-zero patterns of lepton mass matrices from modular symmetry

Texture zeros in fermion mass matrices have been widely considered in tackling the Standard Model flavour puzzle. In this work, we perform a systematic analysis of texture zeros in lepton mass matrices in the framework of {Gamma}_3^{prime}cong {T}^{prime } modular symmetry. Assuming that the lepton fields transform as irreducible representations of T′, we obtain all possible texture-zero patterns for both charged-lepton and neutrino mass matrices which can be achieved from T′ modular symmetry. We provide representative models for the phenomenologically-viable textures which can accommodate the experimental data. The predictions for lepton mixing angles, CP-violating phases, light neutrino masses and effective neutrino mass relevant for neutrinoless double beta decay, are discussed. We find that the minimal viable lepton model depends on only 7 real free parameters including the modulus τ (the corresponding charged-lepton mass matrix contains 4 vanishing entries, and the neutrino mass matrix has 1 texture zero). Finally, we study in detail three benchmark models, one for each neutrino mass generation mechanism considered (Dirac, Majorana via Weinberg operator and Majorana via minimal type-I seesaw mechanism).

Elementary Particle Masses: Alternative Model to the BEH Mechanism

In a first paper [1], we developed a model to calculate the masses of charged leptons by quantifying the electrostatic field generated by these particles. In a second article [2], we extended this model to weak and strong interactions in order to calculate the masses of all elementary fermions. The present paper is a modified version of the second article, adding a hypothesis on the mass of dark matter particles. In this way, the model could be an alternative to the BEH mechanism of the standard model.&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;

Constraints on Neutrino Mass Matrix with no Majorana Phases

In the basis where charged lepton mass matrix is real and diagonal, we havefound conditions under which there are no Majorana phases in neutrino massmatrix. An important feature of the condition is that it has been formulatedin terms of modulus of the elements of neutrino mass matrix independent ofphases. If these conditions are satisfied, a CKM type matrix is enough tomake neutrino Majorana mass matrix real and diagonal without any need ofMajorana phases. As an application, we explore the possibility of Majoranaphases in all phenomenologically acceptable neutrino mass matrices with twotexture zeros.

Deviation to the Tri-Bi-Maximal flavor pattern and equivalent classes

In the model-independent context, the neutrino mass matrix is assumed to be diagonalized by means of a unitary matrix that possesses the Tri-Bi-Maximal (TBM) flavor mixing pattern. We present an analysis where the TBM deviation is explored by considering different forms with texture zeros, for the charged lepton mass matrix. These last mass matrices are classified into equivalent classes. We are interested in the charged lepton mass matrices with the minimum free parameter number, i.e. the maximum number of texture zeros, that allows us to correctly reproduce the reactor mixing angle value. We show a deviation from the TBM pattern in terms of the charged lepton masses as well as the theoretical expressions and their parameter space for the mixing angles. Finally, we present the phenomenological implications of numerical values of the “Majorana-like” phase factors on the neutrinoless double-beta decay.

Five texture zeros in the lepton sector and neutrino oscillations at DUNE

In this work, we have assumed special structures for the charged and neutral mass matrices in the lepton sector, inspired by structures for the up and down quark mass matrices that result by assuming a certain number of symmetrical zeros in their entries named texture zeros. A prediction of the lepton mixing matrix results from the rotation matrices that diagonalize the mass matrices in the neutral and charged lepton sectors. The use of texture zeros reduces the number of spurious parameters to the minimal ones needed to explain observations i.e., charged lepton masses and neutrino oscillation parameters. Specifically, we have considered the case of five texture zeros and we have confronted the resulting lepton mixing matrices with current measurements in the neutrino sector. Finally, sensitivities to the independent parameters in the mixing predicted by the nonequivalent forms were studied using simulated events at the DUNE neutrino oscillation experiment. We have found that DUNE is sensitive to nonzero $CP$ violation allowed in the models.