Neutrino Mass Problem Research Articles

Flavour and dark matter in a scoto/type-II seesaw model

The neutrino mass and dark matter (DM) problems are addressed in a Standard Model extension where the type-II seesaw and scotogenic mechanisms coexist. The model features a flavour \U0001d4b58 discrete symmetry which is broken down to a \U0001d4b52, stabilising the (scalar or fermion) DM particle. Spontaneous CP violation is implemented through the complex vacuum expectation value of a singlet scalar field, inducing observable CP-violating effects in the lepton sector. The structure of the effective neutrino mass matrix leads to constraints on the low-energy neutrino observables, namely the atmospheric neutrino mixing angle θ23, the Dirac CP-violating phase δ and the absolute neutrino mass scale mlightest. In particular, in most cases, the model selects one θ23 octant with δ ≃ 3π/2. Moreover, the obtained lower bounds on mlightest are typically in the range probed by cosmology. We also analyse the constraints imposed on the model by current experimental limits on charged lepton flavour violating (cLFV) processes, as well as future projected sensitivities. It is shown that the Higgs triplet and scotogenic contributions to cLFV never overlap and that the interplay among Yukawa couplings, dark charged scalar masses and mixing leads to a wide parameter-space region compatible with current experimental bounds. We investigate the scalar and fermion DM parameter space of our model by considering relic density, direct-detection (DD) and collider constraints. For scalar DM the mass interval 68 GeV ≲ mDM ≲ 90 GeV is viable and will be probed by future DD searches. In the fermion DM case, correct relic density is always obtained for mDM ≳ 45 GeV thanks to dark fermion-scalar coannihilation channels.

The naturalness in the BLMSSM and B-LSSM

In order to interpret the Higgs boson mass and its decays naturally, we hope to examine the BLMSSM and B-LSSM. In the both models, the right-handed neutrino superfields are introduced to better explain the neutrino mass problems. In this paper, we introduce the fine-tuning to acquire the physical Higgs boson mass. Besides, the method of chi ^2 analyses will be adopted in the BLMSSM and B-LSSM to fit the experimental data. Therefore, we can obtain the reasonable theoretical values of the Higgs decays and muon g-2 that are in accordance with the experimental results respectively in the BLMSSM and B-LSSM.

Consequences of neutrinoless double decays dominated by short ranged interactions

We investigate some consequences if neutrinoless double beta decays of nuclei are dominated by short range interactions. To illustrate our results, we assume that such decays proceed mainly through short range interactions involving two-W-bosons exchanges and confine ourselves to only include new scalars without new gauge interactions for SM fermions. For the neutrino mass problem we propose to solve it by adopting that the active light neutrinos have predominantly Dirac masses and the small Majorana masses induced by the new scalars render them pseudo(quasi)-Dirac particles. This particular aspect of neutrinos may be detectable in the next generation of neutrino oscillation experiments and/or neutrino telescopes. If so this opens a new connection between neutrinoless double beta decays and neutrino physics. We also noted the new physics signals such as high charged scalar states that can be explored in hadron colliders. In particular, we find that a high energy e^- e^- collider will be very useful in testing the origin of lepton number violation which complements neutrinoless double decays studies.

Suppressing the scattering of WIMP dark matter and nucleons in supersymmetric theories

The continuously improving sensitivity of dark matter direct detection experiments has limited the interaction between dark matter and nucleons being increasingly feeble, while the dark matter relic density favors it to take part in weak interactions. After taking into account the constraints from the Large Hadron Collider (LHC) search for Higgs bosons and sparticles, it is becoming difficult for the neutralino dark matter in the Minimal Supersymmetric Standard Model and the Next-to-Minimal Supersymmetric Standard Model to possess these two seemingly paradoxical features in their most natural parameter space for electroweak symmetry breaking due to the limited theoretical structure. In contrast, the seesaw extension of the Next-to-Minimal Supersymmetric Standard Model, which was initially proposed to solve the neutrino mass problem, enables the lightest sneutrino to act as a viable dark matter candidate, readily has these features, and thus, it easily satisfies the constraints from dark matter and LHC experiments. Compared with the Type-I seesaw extension, the dark matter physics in the inverse seesaw extension is more flexible, allowing it to be consistent with the experimental results in broader parameter space. We conclude that weakly interacting massive particles (such as the sneutrino in this study) work well in supersymmetric theories as dark matter candidates.

Neutrino Masses from the Point of View of Economy and Simplicity

In the framework of such basic principles as local gauge invariance, unification of the weak and electromagnetic interactions and spontaneous symmetry breaking in the Standard Model the most economical and simplest possibilities are realized. We discuss the problem of neutrino masses from the point of view of economy and simplicity. It is unlikely that neutrino masses are of the same SM origin as masses of leptons and quarks. The Weinberg effective Lagrangian is the simplest and the most economical, beyond the Standard Model mechanism of the generation of small Majorana neutrino masses. The resolution of the sterile neutrino anomaly and observation of the neutrinoless double $\beta$-decay would be crucial tests of this mechanism.

Common origin of 3.55 keV x-ray line and gauge coupling unification with left-right dark matter

We present a minimal left-right dark matter framework that can simultaneously explain the recently observed 3.55 keV x-ray line from several galaxy clusters and gauge coupling unification at high energy scale. Adopting a minimal dark matter strategy, we consider both left and right handed triplet fermionic dark matter candidates which are stable by virtue of a remnant ${\mathcal{Z}}_{2}\ensuremath{\simeq}(\ensuremath{-}1{)}^{B\ensuremath{-}L}$ symmetry arising after the spontaneous symmetry breaking of left-right gauge symmetry to that of the standard model. A scalar bitriplet field is incorporated whose first role is to allow radiative decay of right handed triplet dark matter into the left handed one and a photon with energy 3.55 keV. The other role this bitriplet field at TeV scale plays is to assist in achieving gauge coupling unification at a high energy scale within a nonsupersymmetric $SO(10)$ model while keeping the scale of left-right gauge symmetry around the TeV corner. Apart from solving the neutrino mass problem and giving verifiable new contributions to neutrinoless double beta decay and charged lepton flavor violation, the model with TeV scale gauge bosons can also give rise to interesting collider signatures like diboson excess, dilepton plus two jets excess reported recently in the large hadron collider data.

Cosmology with self-interacting sterile neutrinos and dark matter: A pseudoscalar model

Short baseline neutrino oscillation experiments have shown hints of the existence of additional sterile neutrinos in the eV mass range. Such sterile neutrinos are incompatible with cosmology because they suppress structure formation unless they can be prevented from thermalizing in the early Universe or removed by subsequent decay or annihilation. Here, we present a novel scenario in which both sterile neutrinos and dark matter are coupled to a new, light pseudoscalar. This can prevent thermalization of sterile neutrinos and make dark matter sufficiently self-interacting to have an impact on galactic dynamics and possibly resolve some of the known problems with the standard cold dark matter scenario. Even more importantly it leads to a strongly self-interacting plasma of sterile neutrinos and pseudoscalars at late times and provides an excellent fit to cosmic microwave background data. The usual cosmological neutrino mass problem is avoided by sterile neutrino annihilation to pseudoscalars. The preferred value of ${H}_{0}$ is substantially higher than in standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ (lambda cold dark matter) and in much better agreement with local measurements.

On the Problem of Neutrino Mass in the Aspect of the Detected Spatial Anisotropy of Temporal Variations of Solar Neutrinos Flux

Mass of the muon and tau-neutrinos are calculated. Set the integer 2:5 ratio between the mass of muon neutrinos and muon ultra-light weight torsion. Found that the calculated mass of the tau-neutrino is the same as the largest with heat 3/2 T relic neutrinos. In the standard model T = 2K. Considering the temperature of the relic neutrinos as the effective gravitational temperature TΓ = 2/9 M for some mass M,it isfollowed ratio M=3mvτ, corresponding to reactions of the dissolution of the relic neutrinos by three sterile active Tau-neutrinos. Solar neutrino flux measurements data and its temporal variations in the Chlorine-Argon experiment for the period 1970-1994, examined with particular attention near dated frontiers of solar activity (FSA), which defined by means of the key criterion of 2ln2 in point a significant manifestation of the influence the Sun eccentric planets. Review shall be carried out within the framework of the standard model, taking into account the gravity. The results are presented in the form of pie charts in a consecutive temporary scan on a direct ascent of Earth's orbital position α, recalculated according to the date of the middle of each of the series of measurements. The corners of the sectors 35° and more defined for temporary length of each dimension.The amplitude of the sector is equal to the measured magnitude of neutrino flow minus the constant component 2.57 SNU. All charts show the priority direction of the solar neutrino flux detector checked by angles α = 271°, δ = 40o (-15o) axis of anisotropy of Galactic Gamma-radiation, as well as a number of less significant in transverse to the axis of the direction. Researched the relationship between solar activity, seismic activity of the Earth and neutrinos flows registered in chlorine-argon experiment for the period 1970-1994, as well as in the SAGE for the period 1970-2008years.There are correlations of solar activity with seismic activity of the Earth and the positive correlation between seismic activity of the Earth and the neutrino flow variations, reaching 95% when taking into account the peculiarities of the matching of dates of solar maximums with FSA dates 1978, 1993-5 and 2002.It turned out that all known and perhaps predicted on 2018 year the greatest average annual values of the flow of solar cosmic rays which defines corresponding dose fall exactly on the years of FSA defined on the planets eccentric.

A model of radiative neutrino mass: with or without dark matter

We present a three-loop model of neutrino mass whose most-general Lagrangian possesses a softly-broken accidental $Z_2$ symmetry. In the limit that a single parameter vanishes, $\lambda\rightarrow0$, the $Z_2$ symmetry becomes exact and the model contains a stable dark-matter candidate. However, even for finite $\lambda\ll1$, long-lived dark matter is possible, giving a unified solution to the neutrino mass and dark matter problems that does not invoke a new symmetry. Taken purely as a neutrino mass model, the new physics can be at the TeV scale. When dark matter is incorporated, however, only a singlet scalar can remain this light, though the dark matter can be tested in direct-detection experiments.

B – L neutralino dark matter

We focus on the supersymetric extension of the gauge group SU(3)c × SU(2)L × U(1)y × U(1)B–L in which we have included the right handed neutrino superfield gauged only under B − L. In this context, it is possible to address the problem of neutrino masses and the DM problem can be tackled via the B – L fermion sector instead of the MSSM one.

Are Photons Massless or Massive?

Prevailing and conventional wisdom as drawn from both Professor Albert Einstein’s Special Theory of Relativity (STR) and our palatable experience, holds that photons are massless particles and that, every particle that travels at the speed of light must—accordingly, be massless. Amongst other important but now resolved problems in physics, this assumption led to the Neutrino Mass Problem—namely, “Do neutrinos have mass?” Neutrinos appear very strongly to travel at the speed of light and according to the afore-stated, they must be massless. Massless neutrinos have a problem in that one is unable to explain the phenomenon of neutrino oscillations because this requires massive neutrinos. Experiments appear to strongly suggest that indeed, neutrinos most certainly are massive particles. While this solves the problem of neutrino oscillation, it directly leads to another problem, namely that of “How can a massive particle travel at the speed of light? Is not this speed a preserve and prerogative of only massless particles?” We argue herein that in principle, it is possible for massive particles to travel at the speed of light. In presenting the present letter, our hope is that this may aid or contribute significantly in solving the said problem of “How can massive particles travel at the speed of light?”

Heavy Neutrinos, Z' and Higgs Bosons at the LHC: New Particles from an Old Symmetry

A new era in particle physics is being spurred on by new data from the Large Hadron Collider. Non-vanishing neutrino masses represent firm observational evidence of new physics beyond the Standard Model. An extension of the latter, based on a SU(3)C × SU(2)L × U(1)Y × U(1)B-L symmetry, incorporating an established Baryon minus Lepton number invariance, is proposed as a viable and testable solution to the neutrino mass problem. We argue that LHC data will probe all the new content of this model: heavy neutrinos, an extra gauge boson emerging from spontaneous breaking of the additional gauge group at the TeV scale, onset by a new heavier Higgs boson, also visible at the CERN proton-proton collider. An even more exciting version of this model is the one exploiting Supersymmetry: firstly, it incurporates all its well-known benefits; secondly, it alleviates the flaws of its more minimal realisations. Finally, this model provides a credible cold Dark Matter candidate, the lightest sneutrino, detectable in both underground and collider experiments.

Bimaximal mixing from lopsided neutrinos

We consider the problem of neutrino masses and mixing within the general framework of standard (type-I) seesaw models leading to three light neutrinos. Under the assumption of a hierarchical neutrino mass spectrum \lambda^4: \lambda : 1, consistent with present data, we examine possible lopsided patterns for the neutrino Yukawa couplings that can account for the observed mixing angles, including a small but non-vanishing |U_{e3}|. An embedding of the above within a general class of SO(10) models is also considered.

Hierarchical neutrino masses and mixing in nonminimalSU(5)

We consider the problem of neutrino masses and mixing within the framework of a nonminimal supersymmetric $SU(5)$ model extended by adding a set of $\underline{\mathbf{1}}$, $\underline{\mathbf{24}}$ chiral superfields accommodating three right-handed neutrinos. A type $\mathrm{I}+\mathrm{III}$ seesaw mechanism can then be realized, giving rise to a hierarchical mass spectrum for the light neutrinos of the form ${m}_{3}>{m}_{2}\ensuremath{\gg}{m}_{1}$, consistent with present data. The extra colored states are pushed to the unification scale by proton stability constraints, while the intermediate seesaw energy scale and the unification scale are maintained in phenomenologically acceptable ranges. We also examine the issue of the large neutrino mixing hierarchy ${\ensuremath{\theta}}_{23}>{\ensuremath{\theta}}_{12}\ensuremath{\gg}{\ensuremath{\theta}}_{13}$ in the above framework of hierarchical neutrino masses.

Stable mass hierarchies and dark matter from hidden sectors in the scale-invariant standard model

Scale invariance may be a classical symmetry which is broken radiatively. This provides a simple way to stabilize the scale of electroweak symmetry breaking against radiative corrections. But for such a theory to be fully realistic, it must actually incorporate a hierarchy of scales, including the Planck and the neutrino mass scales in addition to the electroweak scale. The dark matter sector and the physics responsible for baryogenesis may or may not require new scales, depending on the scenario. We develop a generic way of using hidden sectors to construct a technically-natural hierarchy of scales in the framework of classically scale-invariant theories. We then apply the method to generate the Planck mass and to solve the neutrino mass and dark matter problems through what may be termed the ``scale-invariant standard model.'' The model is perturbatively renormalizable for energy scales up to the Planck mass.

Hierarchical neutrino masses and mixing in flipped-[formula omitted

We consider the problem of neutrino masses and mixing in the framework of flipped SU(5). The right-handed neutrino mass, generated through the operation of a seesaw mechanism by a sector of gauge singlets, leads naturally, at a subsequent level, to the standard seesaw mechanism resulting into three light neutrino states with masses of the desired phenomenological order of magnitude. In this framework we study simple Ansätze for the singlet couplings for which hierarchical neutrino masses emerge naturally as λn:λ:1 or λn:λ2:1, parametrized in terms of the Cabbibo parameter. The resulting neutrino mixing matrices are characterized by a hierarchical structure, in which θ13 is always predicted to be the smallest. Finally, we discuss a possible factorized parametrization of the neutrino mass that, in addition to Cabbibo mixing, encodes also mixing due to the singlet sector.

The three-flavor Pauli model for Majorana neutrinos and the problem of neutrino masses

The three-flavor Pauli model for Majorana neutrinos and the problem of neutrino masses

Radiative corrections to the lightest KK states in theT2/(Z2×Z2′) orbifold

We study radiative corrections localized at the fixed points of the orbifold for the field theory in six dimensions with two dimensions compactified on the T2/(Z2 × Z2') orbifold in a specific realistic model for low energy physics that solves the proton decay and neutrino mass problem. We calculate corrections to the masses of the lightest stable KK modes, which could be the candidates for dark matter.

Status of neutrino masses and mixing and future perspectives

The status of the problem of neutrino masses, mixing and oscillations is discussed. Future perspectives are briefly considered.

Mixed dark matter in Universal Extra Dimension models with TeV scaleWRandZ′

We show that in a class of universal extra dimension (UED) models that solves both the neutrino mass and proton decay problems using low scale left-right symmetry, the dark matter of the Universe consists of an admixture of KK photon and KK right-handed neutrinos. We present a full calculation of the dark matter density in these models taking into account the co-annihilation effects due to near by states such as the scalar partner of the KK photon as well as fermion states near the right-handed KK neutrino. Using the value of the relic CDM density, we obtain upper limits on $R^{-1}$ of about 400-650 GeV and $M_{Z'}\leq 1.5$ TeV, both being accessible to LHC. For a region in this parameter space where the KK right-handed neutrino contributes significantly to the total relic density of dark matter, we obtain a lower bound on the dark matter-nucleon scattering cross section of $10^{-44}$ cm$^2$, which can be probed by the next round of dark matter search experiments.