Light Active Neutrino Masses Research Articles

General approach to neutrino mass mechanisms with sterile neutrinos

We present a mathematical framework for constructing the most general neutrino mass matrices that yield the observed spectrum of light active neutrino masses in conjunction with arbitrarily many heavy sterile neutrinos, without the need to assume a hierarchy between Dirac and Majorana mass terms. The seesaw mechanism is a byproduct of the formalism, along with many other possibilities for generating tiny neutrino masses. We comment on phenomenological applications of this approach, in particular deriving a mechanism to address the long-standing (g−2)μ anomaly in the context of the left-right symmetric model. Published by the American Physical Society 2024

Dark matter and neutrino masses in a Portalino-like model

We explore a Portalino-like model of dark matter and neutrino masses in which right-handed neutrino fields connect gauge neutral operators from the Standard Model and Hidden Sector. Neutrino masses are generated via a seesaw-like mechanism that can explain the light active neutrino masses. The model includes a “Portalino” state that connects the two sectors via the neutrino portal. Dark Matter in this model consists of a hidden sector Dirac fermion that dominantly freezes-out via resonant annihilations into other hidden sector states, which ultimately results in a population of Portalinos. Due to small mixing in the extended neutrino sector these Portalinos tend to be cosmologically long lived, decaying into Standard Model particles leading to constraints on the model from Big Bang Nucleosynthesis and measurements of the Cosmic Microwave Background radiation. Combining these limits with direct constraints on the size of the Portalino–neutrino mixing and the assumptions of the model the viable mass ranges for the Portalino states are found to be {0.02}~hbox {eV}lesssim m_n lesssim {6.4}~hbox {eV} or {489}~{hbox {MeV}} lesssim m_n lesssim TeV. Indirect dark matter signals in the form of highly boosted, mono-energetic Portalinos produced in Dark Matter annihilations provide a target for neutrino telescopes.

INFLATION AND AXION DARK MATTER IN THE 3-3-1 MODEL

We consider a renormalizable theory, which successfully explains the number of Standard Model(SM) fermion families and whose non-SM scalar sector includes an axion dark matter as well asa field responsible for cosmological inflation. In such theory, the axion gets its mass via radiativecorrections at one-loop level mediated by virtual top quark, right handed Majorana neutrinos andSM gauge bosons. Its mass is obtained in the range 4 keV÷ 40 keV, consistent with the onepredicted by XENON1T experiment, when the right handed Majorana neutrino mass is varied from100 GeV up to 350 GeV, thus implying that the light active neutrino masses are generated from a lowscale type I seesaw mechanism. Furthermore, the theory under consideration can also successfullyaccommodates the XENON1T excess provided that the PQ symmetry is spontaneously broken atthe 1010 GeV scale.PACS numbers: 11.30.Fs, 12.15.Ff, 12.60.-i

Fermion masses and mixings, dark matter, leptogenesis and $$g-2$$ muon anomaly in an extended 2HDM with inverse seesaw

We propose a predictive \(Q_4\) flavored 2HDM model, where the scalar sector is enlarged by the inclusion of several gauge singlet scalars and the fermion sector by the inclusion of right-handed Majorana neutrinos. In our model, the \(Q_4\) family symmetry is supplemented by several auxiliary cyclic symmetries, whose spontaneous breaking produces the observed pattern of SM charged fermion masses and quark mixing angles. The light active neutrino masses are generated from an inverse seesaw mechanism at one loop level thanks to a remnant preserved \(Z_2\) symmetry. Our model successfully reproduces the measured dark matter relic abundance and is consistent with direct detection constraints for masses of the DM candidate around \(\sim\) 6.3 TeV. Furthermore, our model is also consistent with the lepton and baryon asymmetries of the Universe as well as with the muon anomalous magnetic moment.

A renormalizable left-right symmetric model with low scale seesaw mechanisms

We propose a low scale renormalizable left-right symmetric theory that successfully explains the observed SM fermion mass hierarchy, the tiny values for the light active neutrino masses and is consistent with the lepton and baryon asymmetries of the Universe, the muon and electron anomalous magnetic moments as well as with the constraints arising from the meson oscillations. In the proposed model the top and exotic quarks obtain masses at tree level, whereas the masses of the bottom, charm and strange quarks, tau and muon leptons are generated from a tree level Universal Seesaw mechanism, thanks to their mixings with the charged exotic vector like fermions. The masses for the first generation SM charged fermions arise from a radiative seesaw mechanism at one loop level, mediated by charged vector like fermions and electrically neutral scalars. The light active neutrino masses are produced from a one-loop level inverse seesaw mechanism mediated by electrically neutral scalar singlets and right handed Majorana neutrinos. Our model is also consistent with the experimental constraints arising from the Higgs diphoton decay rate as well as with the constraints arising from charged lepton flavor violation. We also discuss the Z′ and heavy scalar production at a proton-proton collider.

Fermion spectrum and g-2 anomalies in a low scale 3-3-1 model

We propose a renormalizable theory based on the SU(3)_Ctimes SU(3)_Ltimes U(1)_X gauge symmetry, supplemented by the spontaneously broken U(1)_{L_g} global lepton number symmetry and the S_3 times Z_2 discrete group, which successfully describes the observed SM fermion mass and mixing hierarchy. In our model the top and exotic quarks get tree level masses, whereas the bottom, charm and strange quarks as well as the tau and muon leptons obtain their masses from a tree level Universal seesaw mechanism thanks to their mixing with charged exotic vector like fermions. The masses for the first generation SM charged fermions are generated from a radiative seesaw mechanism at one loop level. The light active neutrino masses are produced from a loop level radiative seesaw mechanism. Our model successfully accommodates the experimental values for electron and muon anomalous magnetic dipole moments.

How low-scale trinification sheds light in the flavor hierarchies, neutrino puzzle, dark matter, and leptogenesis

We propose a low-scale renormalizable trinification theory that successfully explains the flavor hierarchies and neutrino puzzle in the Standard Model (SM), as well as provides a dark matter candidate and also contains the necessary means for efficient leptogenesis. The proposed theory is based on the trinification $\SU{3}{C}\times \SU{3}{L}\times \SU{3}{R}$ gauge symmetry, which is supplemented with an additional flavor symmetry $\U{X}\times Z_{2}^{(1)} \times Z_{2}^{(2)}$. In the proposed model the top quark and the exotic fermions acquire tree-level masses, whereas the lighter SM charged fermions gain masses radiatively at one-loop level. In addition, the light active neutrino masses arise from a combination of radiative and type-I seesaw mechanisms, with the Dirac neutrino mass matrix generated at one-loop level.

Minimal model for the fermion flavor structure, mass hierarchy, dark matter, leptogenesis, and the electron and muon anomalous magnetic moments

We propose a renormalizable theory with minimal particle content and symmetries, that successfully explains the number of Standard Model (SM) fermion families, the SM fermion mass hierarchy, the tiny values for the light active neutrino masses, the lepton and baryon asymmetry of the Universe, the dark matter relic density as well as the muon and electron anomalous magnetic moments. In the proposed model, the top quark and the exotic fermions do acquire tree-level masses whereas the SM charged fermions lighter than the top quark gain one-loop level masses. Besides that, the tiny masses for the light active neutrino are generated from an inverse seesaw mechanism at one-loop level.

Renovation of the Standard Model with Clifford-Dirac algebras for chiral-triplets

Three repetitive chiral fields of quarks and leptons are bundled to form clusters, called chiral-triplets, in the electroweak symmetric regime. Postulating that each chiral-triplets possesses its own Clifford-Dirac algebra with the common Lorentz subalgebra and that the gauge fields and the Higgs field interact with the chiral-triplets, we renovate the Standard Model of elementary particles so that the uncertainties persisted in the Yukawa interactions are reduced. The vertex of the interaction between the Higgs field and the chiral-triplets includes pairs of unipotent matrices and four parameters generating the nine Yukawa coupling constants in the Standard Model. The small masses of light active neutrinos arise from the seesaw mechanism induced from the Majorana mass of the right-handed neutrinos. The Higgs mechanism leads to the Dirac mass matrices which can describe all data of the mass spectra and the flavor mixing matrices in the quark and lepton sectors to high precision.

CP violations in a predictive A4 symmetry model

Abstract We will investigate numerically a seesaw model with $A_4$ flavor symmetry to find allowed regions satisfying the current experimental neutrino oscillation data, then use them to predict physical consequences. Namely, the lightest active neutrino mass is of the order of $\mathcal{O}(10^{-2})$ eV. The effective neutrino mass $|\langle m\rangle|$ associated with neutrinoless double beta decay is in the range $[0.002 \,\mathrm{eV},0.038\,\mathrm{eV}]$ and $[0.048\,\mathrm{eV},0.058\,\mathrm{eV}]$, corresponding to the normal and the inverted hierarchy schemes, respectively. Other relations among relevant physical quantities are shown, so that they can be determined if some of them are confirmed experimentally. The recent data of the baryon asymmetry of the Universe ($\eta_B$) can be explained via leptogenesis caused by the effect of the renormalization group evolution on the Dirac Yukawa couplings, provided the right-handed neutrino mass scale $M_0$ ranges from $\mathcal{O}(10^8)$ GeV to $\mathcal{O}(10^{12})$ GeV for $\tan\beta =3$. This allowed $M_0$ range is different from the scale of $\mathcal{O}(10^{13})$ GeV for other effects that also generate a consistent $\eta_B$ from leptogenesis. The branching ratio of the decay $ \mu \rightarrow\,e\gamma$ may reach future experimental sensitivity for very light values of $M_0$. Hence, it will be inconsistent with the $M_0$ range predicted from the $\eta_B$ data whenever this decay is detected experimentally.

Low scale type I seesaw model for lepton masses and mixings

In contrast to the original type I seesaw mechanism that requires right-handed Majorana neutrinos at energies much higher than the electroweak scale, the so-called low scale seesaw models allow lighter masses for the additional neutrinos. Here we propose an alternative low scale type I seesaw model, where neither linear nor inverse seesaw mechanisms take place, but the spontaneous breaking of a discrete symmetry at an energy scale much lower than the model cutoff is responsible for the smallness of the light active neutrino masses. In this scenario, the model is defined with minimal particle content, where the right-handed Majorana neutrinos can have masses at the $\sim 50\mbox{ GeV}$ scale. The model is predictive in the neutrino sector having only four effective parameters that allow to successfully reproduce the experimental values of the six low energy neutrino observables.

Fermion masses and mixings and some phenomenological aspects of a 3-3-1 model with linear seesaw mechanism

We propose a viable theory based on the $SU(3)_C\times SU(3)_L\times U(1)_X$ gauge group supplemented by the $S_4$ discrete group together with other various symmetries, whose spontaneous breaking gives rise to the current SM fermion mass and mixing hierarchy. In the proposed theory the small light active neutrino masses are generated from a linear seesaw mechanism mediated by three Majorana neutrinos. The model is capable of reproducing the experimental values of the physical observables of both quark and lepton sectors. Our model is predictive in the quark sector having 9 effective parameters that allow to successfully reproduce the four CKM parameters and the six Standard Model (SM) quark masses. In the SM quark sector, there is particular scenario, motivated by naturalness arguments, which allows a good fit for its ten observables, with only six effective parameters. We also study the single heavy scalar production via gluon fusion mechanism at proton-proton collider. Our model is also consistent with the experimental constraints arising from the Higgs diphoton decay rate.

A 3-3-1 model with low scale seesaw mechanisms

We construct a viable 3-3-1 model with two SU(3)_L scalar triplets, extended fermion and scalar spectrum, based on the T^{prime } family symmetry and other auxiliary cyclic symmetries, whose spontaneous breaking yields the observed pattern of SM fermion mass spectrum and fermionic mixing parameters. In our model the SM quarks lighter than the top quark, get their masses from a low scale Universal seesaw mechanism, the SM charged lepton masses are produced by a Froggatt-Nielsen mechanism and the small light active neutrino masses are generated from an inverse seesaw mechanism. The model is consistent with the low energy SM fermion flavor data and successfully accommodates the current Higgs diphoton decay rate and predicts charged lepton flavor violating decays within the reach of the forthcoming experiments.

Viable low-scale model with universal and inverse seesaw mechanisms

We formulate a viable low-scale seesaw model, where the masses for the standard model (SM) charged fermions lighter than the top quark emerge from a universal seesaw mechanism mediated by charged vectorlike fermions. The small light active neutrino masses are produced from an inverse seesaw mechanism mediated by right-handed Majorana neutrinos. Our model is based on the $A_{4} $ family symmetry, supplemented by cyclic symmetries, whose spontaneous breaking produces the observed pattern of SM fermion masses and mixings. The model can accommodate the muon and electron anomalous magnetic dipole moments and predicts strongly suppressed $\mu\rightarrow e\gamma $ and $\tau\rightarrow \mu \gamma $ decay rates, but allows a $\tau \rightarrow e\gamma $ decay within the reach of the forthcoming experiments.

A variant of 3-3-1 model for the generation of the SM fermion mass and mixing pattern

We propose an extension of the 3-3-1 model with an additional symmetry group {Z}_2times {Z}_4times mathrm{U}{(1)}_{L_g} and an extended scalar sector. To our best knowledge this is the first example of a renormalizable 3-3-1 model, which allows explanation the SM fermion mass hierarchy by a sequential loop suppression: tree-level top and exotic fermion masses, 1-loop bottom, charm, tau and muon masses; 2-loop masses for the light up, down, strange quarks as well as for the electron. The light active neutrino masses are generated from a combination of linear and inverse seesaw mechanisms at two loop level. The model also has viable fermionic and scalar dark matter candidates.

A highly predictive A4 flavor 3-3-1 model with radiative inverse seesaw mechanism

We build a highly predictive 3-3-1 model, where the field content is extended by including several SU(3)L scalar singlets and six right handed Majorana neutrinos. In our model the gauge symmetry is supplemented by the discrete group, which allows to get a very good description of the low energy fermion flavor data. In the model under consideration, the discrete group is broken at very high energy scale down to the preserved Z2 discrete symmetry, thus generating the observed pattern of SM fermion masses and mixing angles and allowing the implementation of the loop level inverse seesaw mechanism for the generation of the light active neutrino masses, respectively. The obtained values for the physical observables in the quark sector agree with the experimental data, whereas those ones for the lepton sector also do, only for the case of inverted neutrino mass spectrum. The normal neutrino mass hierarchy scenario of the model is ruled out by the neutrino oscillation experimental data. We find an effective Majorana neutrino mass parameter of neutrinoless double beta decay of mee = 46.9 meV, a leptonic Dirac CP violating phase of −81.37° and a Jarlskog invariant of about 10−2 for the inverted neutrino mass hierarchy. The preserved Z2 symmetry allows for a stable scalar dark matter candidate.

Prediction on neutrino Dirac and Majorana phases and absolute mass scale from the CKM matrix

In the type-I seesaw model, the lepton-flavor-mixing matrix (Pontecorvo-Maki-Nakagawa-Sakata matrix) and the quark-flavor-mixing matrix [Cabibbo-Kobayashi-Maskawa (CKM) matrix] may be connected implicitly through a relation between the neutrino Dirac Yukawa coupling ${Y}_{D}$ and the quark Yukawa couplings. In this paper, we study whether ${Y}_{D}$ can satisfy---in the flavor basis where the charged lepton Yukawa and right-handed neutrino Majorana mass matrices are diagonal---the relation ${Y}_{D}\ensuremath{\propto}\mathrm{diag}({y}_{d},{y}_{s},{y}_{b}){V}_{\mathrm{CKM}}^{T}$ or ${Y}_{D}\ensuremath{\propto}\mathrm{diag}({y}_{u},{y}_{c},{y}_{t}){V}_{\mathrm{CKM}}^{*}$ without contradicting the current experimental data on quarks and neutrino oscillations. We search for sets of values of the neutrino Dirac $CP$ phase ${\ensuremath{\delta}}_{CP}$, Majorana phases ${\ensuremath{\alpha}}_{2}$, ${\ensuremath{\alpha}}_{3}$, and the lightest active neutrino mass that satisfy either of the above relations, with the normal or inverted hierarchy of neutrino masses. In performing the search, we consider renormalization group evolutions of the quark masses and CKM matrix and the propagation of their experimental errors along the evolutions. We find that only the former relation ${Y}_{D}\ensuremath{\propto}\mathrm{diag}({y}_{d},{y}_{s},{y}_{b}){V}_{\mathrm{CKM}}^{T}$ with the normal neutrino mass hierarchy holds, based on which we make predictions for ${\ensuremath{\delta}}_{CP}$, ${\ensuremath{\alpha}}_{2}$, ${\ensuremath{\alpha}}_{3}$, and the lightest active neutrino mass.

Numerical estimate of minimal active-sterile neutrino mixing

Seesaw mechanism constrains from below mixing between active and sterile neutrinos for fixed sterile neutrino masses. Signal events associated with sterile neutrino decays inside a detector at fixed target experiment are suppressed by the mixing angle to the power of four. Therefore sensitivity of experiments such as SHiP and DUNE should take into account minimal possible values of the mixing angles. We extend the previous study of this subject [1] to a more general case of non-zero CP-violating phases in the neutrino sector. Namely, we provide numerical estimate of minimal value of mixing angles between active neutrinos and two sterile neutrinos with the third sterile neutrino playing no noticeable role in the mixing. Thus we obtain a sensitivity needed to fully explore the seesaw type I mechanism for sterile neutrinos with masses below 2 GeV, and one undetectable sterile neutrino that is relevant for the fixedtarget experiments. Remarkably, we observe a strong dependence of this result on the lightest active neutrino mass and the neutrino mass hierarchy, not only on the values of CP-violating phases themselves. All these effects sum up to push the limit of experimental confirmation of sterile-active neutrino mixing by several orders of magnitude below the results of [1] from 10-10 - 10-11 down to 10-12 and even to 10-20 in parts of parameter space; non-zero CP-violating phases are responsible for that.

Fermion masses and mixings in the 3-3-1 model with right-handed neutrinos based on the $$S_3$$ S 3 flavor symmetry

We propose a 3-3-1 model where the $${SU}(3)_{C}\otimes {SU}(3)_{L}\otimes U(1)_{X}$$ symmetry is extended by $$S_{3}\otimes Z_{3}\otimes Z_{3}^{\prime }\otimes Z_{8}\otimes Z_{16}$$ and the scalar spectrum is enlarged by extra $$ {SU}(3)_{L}$$ singlet scalar fields. The model successfully describes the observed SM fermion mass and mixing pattern. In this framework, the light active neutrino masses arise via an inverse seesaw mechanism and the observed charged fermion mass and quark mixing hierarchy is a consequence of the $$Z_{3}\otimes Z_{3}^{\prime }\otimes Z_{8}\otimes Z_{16}$$ symmetry breaking at very high energy. The obtained physical observables for both quark and lepton sectors are compatible with their experimental values. The model predicts the effective Majorana neutrino mass parameter of neutrinoless double beta decay to be $$m_{\beta \beta }=$$ 4 and 48 meV for the normal and the inverted neutrino spectra, respectively. Furthermore, we found a leptonic Dirac CP-violating phase close to $$\frac{\pi }{2}$$ and a Jarlskog invariant close to about $$3\times 10^{-2}$$ for both normal and inverted neutrino mass hierarchy.

A 3-3-1 model with right-handed neutrinos based on the $$\varDelta \left( 27\right) $$ Δ 27 family symmetry

We present the first multiscalar singlet extension of the 3-3-1 model with right-handed neutrinos, based on the $\Delta \left( 27\right) $ family symmetry, supplemented by the $Z_{4}\otimes Z_{8}\otimes Z_{14}$ flavor group, consistent with current low energy fermion flavor data. In the model under consideration, the light active neutrino masses are generated from a double seesaw mechanism and the observed pattern of charged fermion masses and quark mixing angles is caused by the breaking of the $\Delta \left( 27\right) \otimes Z_{4}\otimes Z_{8}\otimes Z_{14}$ discrete group at very high energy. Our model has only 14 effective free parameters, which are fitted to reproduce the experimental values of the 18 physical observables in the quark and lepton sectors. The obtained physical observables for the quark sector agree with their experimental values, whereas those ones for the lepton sector also do, only for the inverted neutrino mass hierarchy. The normal neutrino mass hierarchy scenario of the model is disfavored by the neutrino oscillation experimental data. We find an effective Majorana neutrino mass parameter of neutrinoless double beta decay of $m_{\beta \beta }=$ 22 meV, a leptonic Dirac CP violating phase of $34^{\circ }$ and a Jarlskog invariant of about $10^{-2}$ for the inverted neutrino mass spectrum.