Search

We derive verifiable two-zero textures in the framework of a three-loop induced neutrino mass model applying a modular A 4 symmetry for the lepton sector. Interestingly, the neutrino mass structure is determined by assignments of the right-handed charged-lepton particles only. We show all the possible texture patterns and demonstrate their analytical and numerical analyses. Finally, we mention a possibility of detection for doubly-charged boson via colliders that decays into specific modes due to the flavor symmetry. [ABSTRACT FROM AUTHOR]

We consider a general, anomaly free U (1) ′ extension of the Standard Model (SM) where the neutrino mass is generated at the tree level via the inverse seesaw mechanism. The model contains three right handed neutrinos, three additional singlet fermions, one extra complex scalar and a neutral gauge boson (Z ′). Instead of resorting to a specific U (1) extension, we consider a class of models by taking the U (1) ′ charges of the scalars to be free parameters. Here, we assign one pair of the pseudo-Dirac degenerate sterile neutrinos as Dark Matter (DM) candidates which are produced by the freeze-in mechanism. Considering different mass regimes of the DM, Z ′ and reheating temperature, we obtain constraints on the U (1) ′ charges giving the correct relic abundance. We have also obtained constraints on Z ′ mass and coupling from consideration of relic density as well as high energy collider experiments like ATLAS in case of heavy Z ′ or in intensity and lifetime frontier experiments like DUNE, FASERs, and ILC beam dump which are looking for light Z ′. Additionally, in this model, the decay of pseudo-Dirac DM into active neutrinos can explain the 511 keV line observed by the INTEGRAL satellite. [ABSTRACT FROM AUTHOR]

We propose a scenario where a high scale seesaw origin of light neutrino mass and gravitational dark matter (DM) in MeV-TeV ballpark originating from primordial black hole (PBH) evaporation can be simultaneously probed by future observations of stochastic gravitational wave (GW) background with multiple tilts or spectral breaks. A high scale breaking of an Abelian gauge symmetry ensures the dynamical origin of the seesaw scale while also leading to the formation of cosmic strings responsible for generating stochastic GW background. The requirement of a correct DM relic in this ballpark necessitates the inclusion of a diluter as PBH typically leads to DM overproduction. This leads to a second early matter dominated epoch after PBH evaporation due to the long-lived diluter. These two early matter dominated epochs, crucially connected to the DM relic, lead to multiple spectral breaks in the otherwise scale-invariant GW spectrum formed by cosmic strings. We find interesting correlations between DM mass and turning point frequencies of GW spectrum which are within reach of several near future experiments like LISA, BBO, ET, CE, etc. [ABSTRACT FROM AUTHOR]

We examine the octant sensitivity of the long-baseline neutrino oscillation experiments in view of light sterile neutrino flavors with masses in the 1 eV range. Considering the active-sterile mixing, we explore the possible preferred running modes either neutrino or anti-neutrino for a long-baseline experiment to avoid the octant degeneracy and will show the θ 23 sensitivity for different values of active and sterile neutrino phase angles. We simulated different Long baseline experiments for the different possible combinations of mixing angles and phases and will show whether an experiment can probe the right octant in presence of sterile neutrino by choosing the suitable beam either in neutrino or antineutrino running mode. [ABSTRACT FROM AUTHOR]

Non-zero neutrino mass and dark matter (DM) overshadow the success of the Standard Model (SM) of particle physics. The most straightforward extension of the SM to explain these two issues is the Scotogenic model, where the SM particle spectrum extends with three isospin singlet right-handed neutrinos and one doublet scalar, all odd under a Z 2 symmetry. The neutrino masses and mixings result from the Weinberg operator induced at one-loop level. The particle spectrum of this model contains a few weakly interacting stable massive particles, each of which can be a good candidate for DM. In this work, we have considered the lightest right-handed neutrino as DM candidate. The Yukawa couplings that give rise to the observed flavor mixings in the neutrino sector also lead to flavor violation in the SM charged lepton sector and hence, get tightly constrained from the charged lepton flavor violating (CLFV) observables. The same Yukawa couplings also contribute to the DM annihilation in the early universe and hence, determine the relic density of the DM. In this work, we address the tension between the constraints from CLFV observables and measured DM relic density to obtain the large Yukawa couplings with the help of a parameterization that reduces the phenomenology relevant parameters to merely three and enhances the detection prospect at the collider experiments. We have explored the parameter space consistent with current CLFV bounds, the observed DM relic density, and the absolute neutrino mass limit. To search for these scenarios, we have identified two promising signals at the proposed lepton colliders: the mono-photon plus missing energy and di-lepton plus missing energy signals. We have studied the collider phenomenology of these signatures and estimated the 5 σ detection required luminosity for the center of mass energies at 500 GeV and 1 TeV. [ABSTRACT FROM AUTHOR]

We investigate the properties of neutrino mass matrices that incorporate texture zeros and generalized CP symmetries associated with tribimaximal mixing. By combining these approaches, we derive predictive neutrino mass matrices and explore their implications for mass hierarchies, mixing angles, and CP-violating phases. We find that the three angles defining the generalized CP symmetries have narrow allowed ranges. We also obtain distinct correlations between the three mixing angles and the CP-violating phases that distinguish the various texture patterns from one another. Moreover, we compute the effective neutrino mass for neutrinoless double beta decay and the sum of neutrino masses. Our results highlight the predictability and testability of neutrino mass matrices with generalized CP symmetry. [ABSTRACT FROM AUTHOR]

Results from experiments like LSND and MiniBooNE hint towards the possible presence of an extra eV scale sterile neutrino. The addition of such a neutrino will significantly impact the standard three flavor neutrino oscillations. In particular, it can give rise to additional degeneracies due to additional sterile parameters. For an eV scale sterile neutrino, the cosmological constraints dictate that the sterile state is heavier than the three active states. However, for lower masses of sterile neutrinos, the sterile state can be lighter than one and/or more of the three states. In such cases, the mass ordering of the sterile neutrinos also becomes unknown, along with the mass ordering of the active states. In this paper, we explore the mass ordering sensitivity in the presence of a sterile neutrino assuming the mass squared difference | Δ 41 | to be in the range 10 − 4 − 1 eV2. We study (i) how the ordering of the active states, i.e. the determination of the sign of Δ 31 gets affected by the presence of a sterile neutrino in the above mass range, (ii) the possible determination of the sign of Δ 41 for Δ 41 in the range 10 − 4 − 0.1 eV2. This analysis is done in the context of a liquid argon detector using beam neutrinos traveling a distance of 1300 km and atmospheric neutrinos that propagate through a distance ranging from 10 - 10000 km, allowing resonant matter effects. Apart from presenting separate results from these sources, we also do a combined study and probe the synergy between these two in giving an enhanced sensitivity. [ABSTRACT FROM AUTHOR]

Seesaw mechanisms are the simplest and the most elegant way of generating small masses for the active neutrinos (m ν). In these mechanisms m ν is inversely proportional to the lepton number breaking scale (M) that, in the particular case of the type I seesaw mechanism, is the Majorana mass of the right-handed neutrinos. In the canonical case right-handed neutrinos are supposed to be heavy belonging to the GUT scale. With the advent of the LHC people began to suppose these neutrinos having mass at TeV scale. In this case very tiny Yukawa couplings are required. As far as we know there are no constraints on the energy scales associated to the seesaw mechanisms. In what concern 3-3-1 models, when we trigger the type I seesaw mechanism the lepton number breaking scale that suppresses active neutrino masses contributes to the masses of the standard gauge bosons. Current data on m W demands the mechanism to be performed at GeV scale. As main implication we may have right handed neutrinos with mass varying from few keVs up to hundreds of GeVs. We also investigate the viability of the mechanism and found as interesting result that in the case in which the right-handed neutrino masses belong to the range keV-MeV scale, viability of the mechanism demands that the lightest of the right-handed neutrinos be stable, which makes of it a natural dark matter candidate, and that the lightest of the active neutrinos be ultralight. [ABSTRACT FROM AUTHOR]

Motivated by current experiments on searching for neutrinoless double beta decays, we study the phenomenological consequences and testability of the constraint relation " M i i = M j j + M e μ + M e τ ", for i , j = e , μ , τ , on the magic neutrino mass matrix elements. This hypothesis is inspired by the μ − τ symmetry and gives rise to six different Majorana neutrino mass textures, including two textures one-zero. These obtained textures are diagonalized by the well-known trimaximal mixing which provides nonzero and nonmaximal reactor and atmospheric angles, respectively. Depending on the predominance of the e -row or μ - τ block, the preferred neutrino mass hierarchy and the lower limits on the | M i i | effective Majorana masses for each magic matrix are determined. Furthermore, in light of the global-fit results of neutrino oscillation parameters as reported by NuFIT 5.1, we also study the testability of these textures at the proposed neutrinoless double beta decay experiments such as KamLAND-Zen, GERDA Phase-II and nEXO, by incorporating the effective Majorana neutrino masses | M i j | that are generated through these neutrino mass matrices. [ABSTRACT FROM AUTHOR]

In the 3-3-1 model with right-handed neutrinos (331RHNs), three triplets of scalars engender the correct sequence of symmetry breaking, S U (3) C × S U (3) L × U (1) X → S U (3) C × S U (2) L × U (1) Y → S U (3) C × U (1) EM , generating mass for all fermions, except neutrinos. Tiny neutrino masses may be achieved by implementing the type II seesaw mechanism into the model, requiring the addition of one sextet of scalars to the original scalar content. As consequence, it emerges a very complex scalar sector, involving terms that violate lepton number explicitly, too. The main obstacle to the development of the phenomenology of such scenario is the knowledge of its spectrum of scalars since, now, there are 15 massive scalar particles on it. The proposal of this work is to do an exhaustive analysis of such scalar sector with lepton number being explicitly violated at low, electroweak and high energy scales by means of trilinear terms in the potential. The first case can be addressed analytically and, as a nice result, we have observed that the scalar content of such case is split into two categories: One belonging to the 331 energy scale and the other belonging to the EWSB energy scale, with the last recovering the well know 2THDM + triplet. For the other cases, the scalar sector can be addressed only numerically. Hence, we proposed a very general approach for the numerical study of the potential, avoiding simplifications that can make us reach conclusions without foundation. We show that, in the case of lepton number being explicitly violated at electroweak scale, it is possible to recover the same physics of the 2HDM + triplet, as the previous case. Among all the possibilities, we call the attention to one special case which generates the 3HDM+triplet scenario. For the last case, when lepton number is violated at high energy scale, the sextet becomes very massive and decouples from the original scalar content of the 3-3-1 model. We also discuss, when possible, the phenomenological aspects of each case. [ABSTRACT FROM AUTHOR]

We explore beta decays in a dark background field, which could be formed by dark matter, dark energy or a fifth force potential. In such scenarios, the neutrino's dispersion relation will be modified by its collective interaction with the dark field, which can have interesting consequences in experiments using tritium beta decays to determine the absolute neutrino mass. Among the most general interaction forms, the (pseudo)scalar and (axial-)vector ones are found to have interesting effects on the spectrum of beta decays. In particular, the vector and axial-vector potentials can induce distinct signatures by shifting the overall electron energy scale, possibly beyond the usually defined endpoint. The scalar and pseudoscalar potentials are able to mimic a neutrino mass beyond the cosmological bounds. We have placed stringent constraints on the dark potentials based on the available experimental data of KATRIN. The sensitivity of future KATRIN runs is also discussed. [ABSTRACT FROM AUTHOR]

Abstract We explore the possibility to explain a bosonic dark matter candidate with a gauge singlet inside the loop to generate the neutrino mass matrix at two-loop level. The mass matrix is suppressed by a small mixing that comes from the bound on direct detection experiments of the dark matter, and equivalent of the three-loop neutrino model due to the small mixing between neutral inert bosons. Here, our setup is the Zee-Babu type scenario with Z 3 discrete symmetry, in which we consider the neutrino oscillation data, lepton flavor violations, muon g − 2 , μ − e conversion rate, lepton flavor-changing and conserving Z boson decay and bosonic dark matter candidate. [ABSTRACT FROM AUTHOR]

Abstract We propose a neutrino model in which neutrino masses are generated at one loop level and three right-handed fermions have non-trivial charges under U (1) B − L gauge symmetry in no conflict with anomaly cancellation. After the spontaneously symmetry breaking, a remnant Z 2 symmetry is induced and plays an role in assuring the stability of dark matter candidate. [ABSTRACT FROM AUTHOR]

Abstract We study a model of neutrino within the framework of minimal extended seesaw (MES), which plays an important role in active and sterile neutrino phenomenology in (3+1) scheme. The A 4 flavor symmetry is augmented by additional Z 4 × Z 3 symmetry to constraint the Yukawa Lagrangian of the model. We use non-trivial Dirac mass matrix, with broken μ − τ symmetry, as the origin of leptonic mixing. Interestingly, such structure of mixing naturally leads to the non-zero reactor mixing angle θ 13. Non-degenerate mass structure for right-handed neutrino M R is considered so that we can further extend our study to Leptogenesis. We have also considered three different cases for sterile neutrino mass, M S to check the viability of this model, within the allowed 3 σ bound in this MES framework. [ABSTRACT FROM AUTHOR]

Abstract We consider the L - R symmetric composite model for quarks and leptons where constituent preons possessing some local S U (N) M F metaflavor symmetry are bound by the chiral S O (n) L × S O (n) R gauge metacolor forces. The strengthening of the 't Hooft's anomaly matching condition, when the massless fermion composites are required to complete a single representation of the S U (N) M F rather than some set of its representations, allows to fix the number of basic metaflavors N. Particularly, just eight left-handed and eight right-handed preons and their composites preserving the global chiral symmetry S U (8) L × S U (8) R are turned out to underlie the physical world at small distances that uniquely identifies the local metaflavor symmetry S U (8) M F as its effective unified symmetry. We next show that the spontaneous L - R symmetry violation caused by the simultaneously emerged composite scalars reduces this initially vectorlike S U (8) M F theory down to the conventional S U (5) GUT with an extra local family symmetry S U (3) F and three standard families of quarks and leptons. Though the tiny confinement scale for universal preons composing both quarks and leptons makes it impossible to directly confirm their composite nature, simultaneous emergence of several extra S U (5) × S U (3) F multiplets of heavy composite fermions may help with a model verification. Generally, they may be located at scales from O (100) TeV up to the Planck mass scale depending on an interplay between the compositeness scale and scale of the family symmetry S U (3) F. Some of them through a natural see-saw mechanism provide the physical neutrino masses which, in contrast to conventional picture, appear to follow an inverted family hierarchy. Others mix with ordinary quark-lepton families in a way that there may arise a marked violation of unitarity in the CKM matrix for leptons. [ABSTRACT FROM AUTHOR]

Abstract We study the origin of neutrino mass through lepton-number violation and spontaneous U (1) L μ − L τ symmetry breaking. To accomplish the purpose, we include one Higgs triplet, two singlet scalars, and two vector-like doublet leptons in the U (1) L μ − L τ gauge extension of the standard model. To completely determine the free parameters, we employ the Frampton–Glashow–Marfatia (FGM) two-zero texture neutrino mass matrix as a theoretical input. It is found that when some particular Yukawa couplings vanish, an FGM pattern can be achieved in the model. Besides the explanation of neutrino data, we find that the absolute value of neutrino mass m j can be obtained in the model, and their sum can satisfy the upper bound of the cosmological measurement with ∑ j | m j | < 0.12 eV. The effective Majorana neutrino mass for neutrinoless double-beta decay is below the current upper limit and is obtained as 〈 m β β 〉 = (0.34 , 2.3) × 10 − 2 eV. In addition, the doubly charged Higgs H ± ± decaying to μ ± τ ± final states can be induced from a dimension-6 operator and is not suppressed, and its branching ratio is compatible with the H ± ± → W ± W ± decay when the vacuum expectation value of Higgs triplet is O (0.01) GeV. [ABSTRACT FROM AUTHOR]

Two new neutrino mass matrix textures exhibiting the mixed μ-τ symmetry are proposed. The mass matrices hint for a promising neutrino mixing schemes and find their connections with Δ (27) and A 4 discrete symmetry groups respectively. [ABSTRACT FROM AUTHOR]

We explore an anomaly-free U (1) gauge extended beyond the Standard model (BSM) framework, to account for the baryon asymmetry of the Universe, along with arranging for tiny neutrino mass. Neutrino masses are generated via higher-dimensional operators (HDOs) involving three right-handed neutrinos (RHNs) with gauge charges (4, 4 and −5 respectively) and two BSM scalars. This is an attractive framework as it can accommodate a keV scale dark matter, with the lightest RHN being the candidate. The remaining two RHNs are quasi-degenerate at the TeV-scale, actively participating in the process of resonant leptogenesis through their decay governed by the same set of HDOs. The RHNs being at the TeV scale, make this framework relevant for studying flavored resonant leptogenesis. This TeV-scale resonant leptogenesis, after satisfying the neutrino oscillation data, leads to interesting predictions on the Yukawa sector of the model. The thermal evolution of the baryon asymmetry has followed the experimental results rather accurately in that corner of parameter space. As a matter of fact, this TeV-scale framework which in principle relies on the low scale resonant leptogenesis typically leads to predictions that potentially can be tested at the colliders. In particular, we consider the same-sign dilepton signature that arises from the RHN pair production through the decay of heavy gauge boson of the extra U (1). [ABSTRACT FROM AUTHOR]

We consider an extension of the Georgi-Glashow SU(5) GUT model by a 45-dimensional scalar and a 24-dimensional fermionic representation, where the latter leads to the generation of the observed light neutrino masses via a combination of a type I and a type III seesaw mechanism. Within this scenario, we investigate the viability of predictions for the ratios between the charged lepton and down-type quark Yukawa couplings, focusing on the second and third family. Such predictions can emerge when the relevant entries of the Yukawa matrices are generated from single joint GUT operators (i.e. under the condition of single operator dominance). We show that three combinations are viable, (i) y τ / y b = 3 / 2 , y μ / y s = 9 / 2 , (ii) y τ / y b = 2 , y μ / y s = 9 / 2 , and (iii) y τ / y b = 2 , y μ / y s = 6. We extend these possibilities to three toy models, accounting also for the first family masses, and calculate their predictions for various nucleon decay rates. We also analyze how the requirement of gauge coupling unification constrains the masses of potentially light relic states testable at colliders. [ABSTRACT FROM AUTHOR]

The minimal U (1) X extension of the Standard Model (SM) is a simple and well-motivated extension of the SM, which supplements the SM with the seesaw mechanism for naturally generating the light neutrino masses and offers various interesting phenomenologies. In the model, the U (1) X charge of each SM field is characterized by the U (1) X charge of the SM Higgs doublet with a free parameter x H. Due to the U (1) X charge of the Higgs doublet, the Higgs boson has a trilinear coupling with the Z boson and the U (1) X gauge boson (Z ′). With this coupling, a new process for the associated Higgs boson production with a Z boson arises through a Z ′ boson in the s -channel at high energy colliders. In this paper, we calculate the associated Higgs boson production at high energy colliders and show interesting effects of the new Z ′ boson mediated process, which can be tested in the future. [ABSTRACT FROM AUTHOR]

Within the low scale resonant leptogenesis scenario, the cosmological CP asymmetry may arise by radiative corrections through the charged lepton Yukawa couplings. While in some cases, as one expects, decisive role is played by the λ τ coupling, we show that in specific neutrino textures only by inclusion of the λ μ the cosmological CP violation is generated at 1-loop level. With the purpose to relate the cosmological CP violation to the leptonic CP phase δ , we consider an extension of MSSM with two right handed neutrinos (RHN), which are degenerate in mass at high scales. Together with this, we first consider two texture zero 3 × 2 Dirac Yukawa matrices of neutrinos. These via see-saw generated neutrino mass matrices augmented by single Δ L = 2 dimension five ( d = 5 ) operator give predictive neutrino sectors with calculable CP asymmetries. The latter is generated through λ μ , τ coupling(s) at 1-loop level. Detailed analysis of the leptogenesis is performed. We also revise some one texture zero Dirac Yukawa matrices, considered earlier, and show that addition of a single Δ L = 2 , d = 5 entry in the neutrino mass matrices, together with newly computed 1-loop corrections to the CP asymmetries, give nice accommodation of the neutrino sector and desirable amount of the baryon asymmetry via the resonant leptogenesis even for rather low RHN masses (∼few TeV– 10 7 GeV ). [ABSTRACT FROM AUTHOR]

We consider a version of the low-scale type I seesaw mechanism for generating small neutrino masses, as an alternative to the standard seesaw scenario. It involves two right-handed (RH) neutrinos ν 1 R and ν 2 R having a Majorana mass term with mass M , which conserves the lepton charge L . The RH neutrino ν 2 R has lepton-charge conserving Yukawa couplings g ℓ 2 to the lepton and Higgs doublet fields, while small lepton-charge breaking effects are assumed to induce tiny lepton-charge violating Yukawa couplings g ℓ 1 for ν 1 R , l = e , μ , τ . In this approach the smallness of neutrino masses is related to the smallness of the Yukawa coupling of ν 1 R and not to the large value of M : the RH neutrinos can have masses in the few GeV to a few TeV range. The Yukawa couplings | g ℓ 2 | can be much larger than | g ℓ 1 | , of the order | g ℓ 2 | ∼ 10 − 4 – 10 − 2 , leading to interesting low-energy phenomenology. We consider a specific realisation of this scenario within the Froggatt–Nielsen approach to fermion masses. In this model the Dirac CP violation phase δ is predicted to have approximately one of the values δ ≃ π / 4 , 3 π / 4 , or 5 π / 4 , 7 π / 4 , or to lie in a narrow interval around one of these values. The low-energy phenomenology of the considered low-scale seesaw scenario of neutrino mass generation is also briefly discussed. [ABSTRACT FROM AUTHOR]

We consider an extension of the Standard Model that provide an unified description of eV scale neutrino mass and dark energy. An explicit model is presented by augmenting the Standard Model with an S U ( 2 ) L doublet scalar, a singlet scalar and right handed neutrinos where all of them are assumed to be charged under a global U ( 1 ) X symmetry. A light pseudo-Nambu–Goldstone Boson, associated with the spontaneously broken U ( 1 ) X symmetry, acts as a mediator of an attractive force leading to a Dirac neutrino condensate, with large correlation length, and a non-zero gap in the right range providing a cosmologically feasible dark energy scenario. The neutrino mass is generated through the usual Dirac seesaw mechanism. Parameter space, reproducing viable dark energy scenario while having neutrino mass in the right ballpark, is presented. [ABSTRACT FROM AUTHOR]

We consider the feasibility of interpreting the R K ( ⁎ ) anomaly in the colored Zee–Babu model. The model generates neutrino masses at two loops with the help of a scalar leptoquark S ∼ ( 3 , 3 , − 1 3 ) and a scalar diquark ω ∼ ( 6 , 1 , − 2 3 ) , and contributes to the transition b → s ℓ − ℓ + via the exchange of a leptoquark S at tree level. Under constraints from lepton flavor violating (LFV) and flavor changing neutral current (FCNC) processes, and direct collider searches for heavy particles, we acquire certain parameter space that can accommodate the R K ( ⁎ ) anomaly for both normal (NH) and inverted (IH) hierarchies of neutrino masses. We further examine the LFV decays of the B meson, and find a strong correlation with the neutrino mass hierarchy, i.e., Br ( B + → K + μ ± τ ∓ ) ≳ Br ( B + → K + μ ± e ∓ ) ≈ Br ( B + → K + τ ± e ∓ ) for NH, while Br ( B + → K + μ ± τ ∓ ) ≪ Br ( B + → K + μ ± e ∓ ) ≈ Br ( B + → K + τ ± e ∓ ) for IH. Among these decays, only B + → K + μ ± e ∓ in the case of NH is promising at the LHCb RUN II, while for IH all LFV decays are hard to detect in the near future. [ABSTRACT FROM AUTHOR]

We show that a high-scale leptogenesis can be consistent with a low-scale one-loop neutrino mass generation. Our models are based on the S U ( 3 ) c × S U ( 2 ) L × U ( 1 ) Y × U ( 1 ) B − L gauge groups. Except a complex singlet scalar for the U ( 1 ) B − L symmetry breaking, the other new scalars and fermions (one scalar doublet, two or more real scalar singlets/triplets and three right-handed neutrinos) are odd under an unbroken Z 2 discrete symmetry. The real scalar decays can produce an asymmetry stored in the new scalar doublet which subsequently decays into the standard model lepton doublets and the right-handed neutrinos. The lepton asymmetry in the standard model leptons then can be partially converted to a baryon asymmetry by the sphaleron processes. By integrating out the heavy scalar singlets/triplets, we can realize an effective theory to radiatively generate the small neutrino masses at the TeV scale. Furthermore, the lightest right-handed neutrino can serve as a dark matter candidate. [ABSTRACT FROM AUTHOR]

The neutral component of an inert scalar multiplet with hypercharge can provide a stable dark matter particle when its real and imaginary parts have a splitting mass spectrum. Otherwise, a tree-level dark-matter-nucleon scattering mediated by the Z boson will be much above the experimental limit. In this paper we focus on a mixed inert scalar triplet dark matter scenario where a complex scalar triplet with hypercharge can mix with another real scalar triplet without hypercharge through their renormalizable coupling to the standard model Higgs doublet. We consider three specified cases that carry most of the relevant features of the full parameter space: (i) the neutral component of the real triplet dominates the dark matter particle, (ii) the neutral component of the complex triplet dominates the dark matter particle; and (iii) the neutral components of the real and complex triplets equally constitute the dark matter particle. Subject to the dark matter relic abundance and direct detection constraint, we perform a systematic study on the allowed parameter space with particular emphasis on the interplay among triplet-doublet terms and gauge interactions. In the presence of these mixed inert scalar triplets, some heavy Dirac fermions composed of inert fermion doublets can be utilized to generate a tiny Majorana neutrino mass term at one-loop level and realize a successful leptogenesis for explaining the cosmic baryon asymmetry. [ABSTRACT FROM AUTHOR]

We present calculations showing how electron rest mass influences entropy flow, neutrino decoupling, and Big Bang Nucleosynthesis (BBN) in the early universe. To elucidate this physics and especially the sensitivity of BBN and related epochs to electron mass, we consider a parameter space of rest mass values larger and smaller than the accepted vacuum value. Electromagnetic equilibrium, coupled with the high entropy of the early universe, guarantees that significant numbers of electron–positron pairs are present, and dominate over the number of ionization electrons to temperatures much lower than the vacuum electron rest mass. Scattering between the electrons–positrons and the neutrinos largely controls the flow of entropy from the plasma into the neutrino seas. Moreover, the number density of electron–positron-pair targets can be exponentially sensitive to the effective in-medium electron mass. This entropy flow influences the phasing of scale factor and temperature, the charged current weak-interaction-determined neutron-to-proton ratio, and the spectral distortions in the relic neutrino energy spectra. Our calculations show the sensitivity of the physics of this epoch to three separate effects: finite electron mass, finite-temperature quantum electrodynamic (QED) effects on the plasma equation of state, and Boltzmann neutrino energy transport. The ratio of neutrino to plasma–component energy scales manifests in Cosmic Microwave Background (CMB) observables, namely the baryon density and the radiation energy density, along with the primordial helium and deuterium abundances. Our results demonstrate how the treatment of in-medium electron mass (i.e., QED effects) could translate into an important source of uncertainty in extracting neutrino and beyond-standard-model physics limits from future high-precision CMB data. [ABSTRACT FROM AUTHOR]

Leptoquarks have been proposed as a possible explanation of anomalies in B ¯ ↦ D ⁎ τ ν ¯ decays, the apparent anomalies in ( g − 2 ) μ experiments and a violation of lepton universality. Motivated by this, we examine other motivations of leptoquarks: radiatively induced neutrino masses in the presence of a discrete symmetry that prevents a tree level see-saw mechanism, gauge coupling unification, and vacuum stability at least up to the unification scale. We present a new model for radiatively generating a neutrino mass which can significantly improve gauge coupling unification at one loop. We discuss this, and other models in the light of recent work on flavour anomalies. [ABSTRACT FROM AUTHOR]

The naturalness of electroweak scale in the models of type-I seesaw mechanism with O ( 1 ) Yukawa couplings requires TeV scale masses for the fermion singlets. In this case, the tiny neutrino masses have to arise from the cancellations within the seesaw formula which are arranged by fine-tuned correlations between the Yukawa couplings and the masses of fermion singlets. We motivate such correlations through the framework of discrete symmetries. In the case of three Majorana fermion singlets, it is shown that the exact cancellation arranged by the discrete symmetries in seesaw formula necessarily leads to two mass degenerate fermion singlets. The remaining fermion singlet decouples completely from the standard model. We provide two candidate models based on the groups A 4 and Σ ( 81 ) and discuss the generic perturbations to this approach which can lead to the viable neutrino masses. [ABSTRACT FROM AUTHOR]

New physics coupling to the Higgs sector of the Standard Model can lead to dangerously large corrections to the Higgs mass. We investigate this problem in the type II seesaw model for neutrino mass, where a weak scalar triplet is introduced. The interplay of direct and indirect constraints on the type II seesaw model with its contribution to the Higgs mass is analyzed. The focus lies on testable triplet masses and (sub) eV-scale triplet vacuum expectation values. We identify scenarios that are testable in collider and/or lepton flavor violation experiments, while satisfying the Higgs naturalness criterion. [ABSTRACT FROM AUTHOR]

The lepton flavor violating decay of the Standard Model-like Higgs boson (LFVHD), h → μ τ , is discussed in seesaw models at the one-loop level. Based on particular analytic expressions of Passarino–Veltman functions, the two unitary and 't Hooft Feynman gauges are used to compute the branching ratio of LFVHD and compare with results reported recently. In the minimal seesaw (MSS) model, the branching ratio was investigated in the whole valid range 10 − 9 – 10 15 GeV of new neutrino mass scale m n 6 . Using the Casas–Ibarra parameterization, this branching ratio enhances with large and increasing m n 6 . But the maximal value can reach only order of 10 − 11 . Interesting relations of LFVHD predicted by the MSS and inverse seesaw (ISS) model are discussed. The ratio between two LFVHD branching ratios predicted by the ISS and MSS is simply m n 6 2 μ X − 2 , where μ X is the small neutrino mass scale in the ISS. The consistence between different calculations is shown precisely from analytical approach. [ABSTRACT FROM AUTHOR]

We compute the probability densities of the effective neutrino masses m β and m β β using the Kernel Density Estimate (KDE) approach applied to a distribution of points in the ( m min , m β β ) and ( m β , m β β ) planes, obtained using the available Probability Distribution Functions (PDFs) of the neutrino mixing angles and mass differences, with the additional constraints coming from cosmological data on the sum of the neutrino masses. We show that the reconstructed probability densities strongly depend on the assumed set of cosmological data: for ∑ j m j ≤ 0.68 eV at 95 % CL a sensitive portion of the allowed values are already excluded by null results of experiments searching for m β β and m β , whereas in the case ∑ j m j ≤ 0.23 eV at 95 % CL the bulk of the probability densities are below the current bounds. [ABSTRACT FROM AUTHOR]

The theory of neutrino oscillation predicts that if both neutrino and antineutrino coming from Z 0 decay are detected, one can observe an oscillation pattern between the corresponding detectors. This prediction is based on two properties; the neutrino-antineutrino pairs are produced coherently and they are detected with definite flavor in detectors. In this paper, we reanalyze this problem with considering some massive neutrinos which are mixed with the light neutrinos but they either participate incoherently or are decoupled in the production and detection processes. In fact, neutrinos whose masses are larger than the upper bound on the mass uncertainty to be compatible with the coherence conditions (we will see it is about 1 keV) must be treated incoherently. Very heavy neutrinos whose masses are much larger than the neutrino energy in the neutrino production process are decoupled. Under these conditions, the created neutrino-antineutrino state as well as the states of detected neutrino and antineutrino is mixed. We see that the oscillation pattern cannot be observed for incoherent neutrinos and the standard oscillation pattern is recovered if the light neutrino masses are ignored in the production and detection processes. Moreover, since the Z 0 decay process is performed blindly with respect to flavors, the oscillating contributions in the event rates are independent of the Z 0 decay width. [ABSTRACT FROM AUTHOR]

The neutrino mass ordering is one of the principal unknowns in the neutrino sector. Long baseline neutrino experiments have the potential of resolving this issue as they are sensitive to large matter effects. The superbeam experiment DUNE is one of the most promising candidates to study the neutrino mass hierarchy, along with NO ν A and T2K. But in the presence of non-unitarity of the leptonic mixing matrix, the capability of such experiments to discriminate between the two hierarchies gets suppressed. The mass hierarchy sensitivity of DUNE decreases in the presence of new physics. In this paper we analyze the origin and extent of this loss of sensitivity at the level of oscillation probabilities, events, mass hierarchy sensitivity and the discovery reach of DUNE, NO ν A and T2K. [ABSTRACT FROM AUTHOR]

In this work we investigate the sensitivity to the neutrino mass hierarchy, the octant of the mixing angle θ 23 and the CP phase δ C P in the future long baseline experiments T2HK and DUNE as well as in the atmospheric neutrino observation at Hyperkamiokande (HK). We show for the first time that the sensitivity is enhanced greatly if we combine these three experiments. Our results show that the hierarchy sensitivity of both T2HK and HK are limited due to the presence of parameter degeneracy. But this degeneracy is removed when T2HK and HK are added together. With T2HK + HK (DUNE), the neutrino mass hierarchy can be determined at least at 5 σ (8 σ ) C.L. for any value of true δ C P . With T2HK + HK + DUNE the significance of the mass hierarchy increases to almost 15 σ for the unfavorable value of δ C P . For this combined setup, octant can be resolved except 43.5 ° < θ 23 < 48 ° at 5 σ C.L. for both the hierarchies irrespective of the value of δ C P . The significance of CP violation is around 10 σ C.L. for δ C P ∼ ± 90 ° . Apart from that this combined facility has the capability to discover CP violation for at least 68 % fraction of the true δ C P values at 5 σ for any value of true θ 23 . We also find that, with combination of all these three, the precision of Δ m eff 2 , sin 2 ⁡ θ 23 and δ C P becomes 0.3%, 2% and 20% respectively. We also clarify how the octant degeneracy occurs in the HK atmospheric neutrino experiment. [ABSTRACT FROM AUTHOR]

Gauged U ( 1 ) L μ − L τ model has been advocated for a long time in light of muon g − 2 anomaly, which is a more than 3 σ discrepancy between the experimental measurement and the standard model prediction. We augment this model with three right-handed neutrinos ( N e , N μ , N τ ) and a vector-like singlet fermion ( χ ) to explain simultaneously the non-zero neutrino masses and dark matter content of the Universe, while satisfying the anomalous muon g − 2 constraints. We find that the model suffers stringent constraints from the simultaneous explanation of neutrino trident production and muon g − 2 anomaly. In a large region of the parameter space, where contribution to muon g − 2 anomaly comes partially and yet not ruled out by neutrino trident production, the model can explain the positron excess, observed at PAMELA, Fermi-LAT and AMS-02 through dark matter annihilation, while satisfying the relic density and direct detection limits. [ABSTRACT FROM AUTHOR]

The Minimal Supersymmetric Extension of the Standard Model (MSSM) is able to explain the current data from neutrino physics. Unfortunately Split Supersymmetry as low energy approximation of this theory fails to generate a solar square mass difference, including after the addition of bilinear R-Parity Violation. In this work, it is shown how one can derive an effective low energy theory from the MSSM in the spirit of Split Supersymmetry, which has the potential of explaining the neutrino phenomenology. This is achieved by going beyond leading order in the process of integrating out heavy scalars from the original theory, which results in non-renormalizable operators in the effective low energy theory. It is found that in particular a d = 8 operator is crucial for the generation of the neutrino mass differences. [ABSTRACT FROM AUTHOR]

We extend some two Higgs doublet models, where the Yukawa couplings for the charged fermion mass generation only involve one Higgs doublet, by two singlet scalars respectively carrying a singly electric charge and a doubly electric charge. The doublet and singlet scalars together can mediate a two-loop diagram to generate a tiny Majorana mass matrix of the standard model neutrinos. Remarkably, the structure of the neutrino mass matrix is fully determined by the symmetric Yukawa couplings of the doubly charged scalar to the right-handed leptons. Meanwhile, a one-loop induced neutrinoless double beta decay can arrive at a testable level even if the electron neutrino has an extremely small Majorana mass. We also study other experimental constraints and implications including some rare processes and Higgs phenomenology. [ABSTRACT FROM AUTHOR]

Radiative neutrino mass generation within supersymmetric (SUSY) construction is studied. The mechanism is considered where the lepton number violation is originating from the soft SUSY breaking terms. This requires MSSM extensions with states around the TeV scale. We present several explicit realizations based on extensions either by MSSM singlet or S U ( 2 ) w triplet states. Besides some novelties of the proposed scenarios, various phenomenological implications are also discussed. [ABSTRACT FROM AUTHOR]

We present a study of resonant leptogenesis in a radiative seesaw model. We consider the case where two quasi-degenerate right-handed neutrinos realize resonant leptogenesis, and the CP violation necessary to achieve leptogenesis occurs through the CP phases present in the neutrino mixing matrix. A numerical analysis is performed by taking the best-fit values from the current global data for three neutrino mixing angles and two mass-squared differences. We have shown how the predicted value of baryon asymmetry depends on the Dirac and Majorana CP phases. With the particular choice for the mass parameters, this model prefers a normal hierarchy of neutrino masses based on the value of baryon asymmetry predicted. Using the constrained CP phases, we evaluate the effective neutrino mass, which is relevant to the neutrinoless double beta decay. [ABSTRACT FROM AUTHOR]

We extend the S U (3) c × S U (2) L × U (1) Y standard model by a U (1) Y ′ gauge symmetry. Three right-handed neutrinos are introduced to cancel the gauge anomaly. One Higgs singlet is responsible for spontaneously breaking the U (1) Y ′ symmetry while the standard model Higgs doublet does not carry any U (1) Y ′ charges. The down-type quarks, up-type quarks, charged leptons and neutral neutrinos obtain their Dirac masses through four types of dimension-5 operators constructed by the fermion doublets and singlets with the Higgs doublet and singlet. This effective theory is realized in three renormalizable contexts with heavy fermion singlets, scalar doublets and fermion doublets. The heavy fermion singlets and doublets for generating the neutrino masses also accommodate a successful Dirac leptogenesis to explain the baryon asymmetry in the universe. [ABSTRACT FROM AUTHOR]

We present a low-scale type-I seesaw scenario with discrete flavor and CP symmetries. This scenario not only explains the measured values of the lepton mixing angles, but also makes predictions for leptonic CP violation, and connects the low-energy CP phases relevant for neutrino oscillation and neutrinoless double beta decay experiments with the high-energy CP phases relevant for leptogenesis. We show that the three right-handed Majorana neutrinos in this scenario have (almost) degenerate masses and their decays can explain the observed baryon asymmetry of the Universe via resonant leptogenesis. We study the correlation of the predicted baryon asymmetry with lepton-number-violating signals at high-energy colliders, including both prompt and displaced vertex/long-lived signatures, as well as in low-energy neutrinoless double beta decay experiments. We find that the normal ordering of light neutrino masses leads to an enhanced collider signal, whereas the neutrinoless double beta decay provides a promising probe in the inverted ordering case. [ABSTRACT FROM AUTHOR]

We investigate the viability of predictive schemes for quark-lepton Yukawa ratios and nucleon decay in non-supersymmetric SU(5) Grand Unified Theories (GUTs) where neutrino masses are generated by a type II seesaw mechanism. The scalar sector of the considered scenario contains 5-, 24- and 45-dimensional representations plus a 15-dimensional representation for realizing the type II seesaw. Predictions for the ratios of the quark and lepton Yukawa couplings emerge when the relevant entries of the Yukawa matrices are generated from single joint GUT operators (i.e. under the condition of single operator dominance). Focusing on the 2nd and 3rd family and hierarchical Yukawa matrices, we show that only two sets of predictions, y τ y b = 3 2 , y μ y s = 9 2 and y τ y b = 2 , y μ y s = 6 are viable. To further investigate both options, we extend the minimal scenarios to two "toy models", including the 1st family of charged fermions, and calculate the models' predictions, e.g. for the nucleon decay rates and for the masses of the light relics that are potentially within reach of colliders. [ABSTRACT FROM AUTHOR]

We study the neutrinoless double beta decay in the colored Zee-Babu model. We consider three cases of the colored Zee-Babu model with a leptoquark and a diquark introduced. The neutrino masses are generated at two-loop level, and the constraints given by tree-level flavor violation processes and muon anomalous magnetic moment (g − 2) μ have been considered. In our numerical analysis, we find that the standard light neutrino exchange contribution can be canceled by new physics contribution under certain assumption and condition, leading to a hidden neutrinoless double beta decay. The condition can be examined comprehensively by future complementary searches with different isotopes. [ABSTRACT FROM AUTHOR]

We propose an S U (3) C × S U (2) L × U (1) Y × U (1) B − L model, in which the neutrino masses and mixings can be generated via Type-I seesaw mechanism after U (1) B − L breaking. A light mediator emerges and enables non-standard interaction that violates the lepton number. We show that the non-standard neutrino interaction emerges in this model, and it can lead to low energy recoil events with the solar neutrino flux. Analyses are performed with the keV range electron recoil events at recent direct detection experiments, including XENON1T, PANDAX and XENONnT. Recent direct detection observations lead to upper bound on the combined coupling strength to electron and neutrino to y ν ′ y e < 0.5 × 10 − 6. [ABSTRACT FROM AUTHOR]

We build the first 3-3-1 model based on the Δ ( 27 ) discrete group symmetry, consistent with fermion masses and mixings. In the model under consideration, the neutrino masses are generated from a combination of type-I and type-II seesaw mechanisms mediated by three heavy right-handed Majorana neutrinos and three SU ( 3 ) L scalar antisextets, respectively. Furthermore, from the consistency of the leptonic mixing angles with their experimental values, we obtain a non-vanishing leptonic Dirac CP violating phase of − π 2 . Our model features an effective Majorana neutrino mass parameter of neutrinoless double beta decay, with values m β β = 10 and 18 meV for the normal and the inverted neutrino mass hierarchies, respectively. [ABSTRACT FROM AUTHOR]

We study a second CP symmetry compatible with the A 4 flavor group, which interchanges the representations 1 ′ and 1 ″ . We analyze the lepton mixing patterns arising from the A 4 and CP symmetry broken to residual subgroups Z 3 and Z 2 × C P in the charged lepton and neutrino sectors respectively. One phenomenologically viable mixing pattern is found, and it predicts maximal atmospheric mixing angle as well as maximal Dirac CP phase, trivial Majorana phases and the correlation sin 2 ⁡ θ 12 cos 2 ⁡ θ 13 = 1 / 3 . We construct a concrete model based on the A 4 and CP symmetry, the above interesting mixing pattern is achieved, the observed charged lepton mass hierarchy is reproduced, and the reactor mixing angle θ 13 is of the correct order. [ABSTRACT FROM AUTHOR]

Within the framework of inverse seesaw mechanism we investigate neutrino mass matrices invariant under cyclic symmetry ( Z 3 ) with maximal zero texture (6 zero textures). We explore two different approaches to obtain the cyclic symmetry invariant form of the constituent matrices. In the first one we consider explicit cyclic symmetry in the neutrino sector of the Lagrangian which dictates the emerged effective neutrino mass matrix ( m ν ) to be symmetry invariant and hence leads to a degeneracy in masses. We then consider explicit breaking of the symmetry through a dimensionless parameter ϵ ′ to remove the degeneracy. It is seen that the method doesn't support the current neutrino oscillation global fit data even after considering the correction from cyclic symmetry invariant charged lepton mass matrix ( m l ) unless the breaking parameter is too large. In the second method, we assume the same forms of the neutrino mass matrices, however, symmetry is broken in the charged lepton sector. All the structures of the mass matrices are now dictated by an effective residual symmetry of some larger symmetry group in the Lagrangian. For illustration, we exemplify a toy model based on softly broken A 4 symmetry group which leads to one of the combinations of m l , m D , M R S and μ to generate effective m ν . All the emerged mass matrices predict a constraint range of the CP violating phases and atmospheric mixing angle along with an inverted hierarchical structure of the neutrino masses. Further, significant predictions on β β 0 ν decay parameter | m 11 | and the sum of the three light neutrino masses ( Σ i m i ) are also obtained. [ABSTRACT FROM AUTHOR]

The neutrino masses and mixings are studied in the model which is the supersymmetric extension of the standard model with local gauged baryon and lepton numbers (BLMSSM). At tree level the neutrinos can obtain tiny masses through the See-Saw mechanism in the BLMSSM. The one-loop corrections to the neutrino masses and mixings are important, and they are studied in this work with the mass insertion approximation. We study the numerical results and discuss the allowed parameter space of BLMSSM. It can contribute to study the neutrino masses and to explore the new physics beyond the standard model (SM). [ABSTRACT FROM AUTHOR]

Neutrino oscillations provide evidence for the mode entanglement of neutrino mass eigenstates in a given flavour eigenstate. Given this mode entanglement, it is pertinent to consider the relation between the oscillation probabilities and other quantum correlations. In this work, we show that all the well-known quantum correlations, such as the Bell's inequality, are directly related to the neutrino oscillation probabilities. The results of the neutrino oscillation experiments, which measure the neutrino survival probability to be less than unity, imply Bell's inequality violation. [ABSTRACT FROM AUTHOR]