arXiv subjects

Ng. K. Francis

Publications and source records attributed to Ng. K. Francis.

18 recordsLinked to original sources

arXiv2026

Connecting Neutrino Masses, Dark Matter and Leptogenesis from $Δ(54)$ Flavor with Triple Inverse Seesaw

In this present study, an extended Delta 54 flavor symmetry model incorporating two standard model Higgs doublets is investigated. This model generates neutrino masses through the triple inverse seesaw mechanism. It predicts deviations from tribimaximal mixing, yielding a nonzero reactor angle and an atmospheric mixing angle in the upper octant. In addition, the CP-violating phase and the Jarlskog invariant are found to be consistent with current neutrino oscillation data. Our study also includes the dark matter sector by evaluating the relic abundance and active neutrino dark matter mixing under relevant cosmological constraints. Furthermore, baryogenesis is achieved through resonant leptogenesis at the TeV scale including flavor effects. We obtain the observed baryon asymmetry, for right-handed neutrino mass 10 TeV and mass splitting d.

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arXiv2025

Phenomenological Implications of $\boldsymbol{Δ(54)}$ Flavor Symmetry with Triple Inverse Seesaw

We present an extension of the $Δ(54)$ flavor symmetry model by incorporating two Standard Model Higgs fields. We generated the neutrino mass matrices with the Triple Inverse Seesaw mechanism. Our numerical analysis reveals deviations from tribimaximal neutrino mixing resulting in a nonzero reactor angle ($θ_{13}$). The atmospheric oscillation parameter ($θ_{23}$) occupies the upper octant. The model predicts Normal Hierarchy (NH) for neutrino masses. The best-fit value is obtained with minimum $χ^2$ analysis. The prediction of the modified model on CP-violating parameters, effective Majorana mass, and Neutrinoless double beta decay phenomenological investigations are found to be in congruous with the current neutrino oscillation data.

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arXiv2024

Relic Abundance of Dark Matter with $Δ$(54) Flavor Symmetry

In this work we discuss the neutrino phenomenology in a $Δ(54)$ discrete flavor symmetry and evaluate the relic abundance of dark matter (DM) and active neutrino-DM mixing angle considering various cosmological constraints. We introduced two Standard Model Higgs particles along with vector-like fermions and a new particle (S) which is a gauge singlet in the Standard Model. This modification leads to a mass matrix that diverges from the tribimaximal neutrino mixing pattern resulting in a non-zero reactor angle ($θ_{13}$). We also incorporated a $ Z_2 \otimes Z_3 \otimes Z_4$ symmetry for the specific interactions in our model. The additional particle S is a sterile neutrino which is considered to be a probable dark matter candidate with mass in keV range.

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arXiv2024

Resonant leptogenesis in minimal inverse seesaw ISS(2,2) model

We investigate the parameter space of the minimal inverse seesaw ISS(2,2) model for successful leptogenesis. The framework of ISS(2, 2) is realized by augmenting the Standard Model with two right-handed and two Standard Model singlet neutrinos. The decay of the heavy sterile states which is essentially an admixture of the right-handed and SM singlet neutrino states produces the baryon asymmetry of the universe. In this predictive model of leptogenesis, we study resonant leptogenesis where the mass splitting between the heavy sterile states is naturally achieved. We review the possibility of generating the observed baryon asymmetry of the universe via leptogenesis where the CP violation comes solely from the low-energy CP phases. In addition, we study the effect of texture zero in the Dirac mass matrix on the parameter space of the model for successful resonant leptogenesis.

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arXiv2024

Neutrino Mixing and Resonant Leptogenesis in Inverse Seesaw and Δ(54) Flavor Symmetry

The current work involves augmenting the $Δ(54)$ discrete flavor model by incorporating two Standard Model Higgs particles into the Inverse Seesaw mechanism. We introduced Weyl fermions and Vector like fermions, which are gauge singlets in the Standard Model and produces Majorana mass terms in our lagrangian. The resulting mass matrix deviates from the tribimaximal neutrino mixing pattern producing a non-zero reactor angle ($θ_{13}$) . We have determined the effective Majorana neutrino mass, which is the parameter of relevance in neutrinoless double beta decay investigations, using the model's limited six-dimensional parameter space. We additionally investigate the possibility of baryogenesis in the proposed framework via resonant leptogenesis. We have the non-zero value for resonantly enhanced CP asymmetry originating from the decay of right-handed neutrinos at the TeV scale, accounting for flavor effects. The evolution of lepton asymmetry is systematically analyzed by numerically solving a set of Boltzmann equations, leading to the determination of the baryon asymmetry with a magnitude of $ \lvert η_B \rvert \approx 6 \times 10^{-10}$. This outcome is achieved by selecting specific values for the right-handed neutrino mass $M_1 = 10$ TeV and mass splitting, $d \approx 10^{-8}$.

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arXiv2023

Neutrino Mass Model in the Context of $\boldsymbol{Δ(54) \otimes Z_2\otimes Z_3 \otimes Z_4}$ Flavor Symmetries with Inverse Seesaw Mechanism

Our analysis involves enhancing the $Δ(54)$ flavor symmetry model with Inverse Seesaw mechanism along with two SM Higgs through the incorporation of distinct flavons. Additionally, we introduce supplementary $Z_2\otimes Z_3 \otimes Z_4$ symmetries to eliminate any undesirable components within our investigation. The exact tri-bimaximal neutrino mixing pattern undergoes a deviation as a result of the incorporation of extra flavons, leading to the emergence of a non-zero reactor angle $θ_{13}$ that aligns with the latest experimental findings. It was found that for our model the atmospheric oscillation parameter occupies the lower octant for normal hierarchy case. We also examine the parameter space of the model for normal hierarchy to explore the Dirac CP ($δ_{CP}$), Jarlskog invariant parameter ($J$) and the Neutrinoless double-beta decay parameter ($m_{ββ}$) and found it in agreement with the neutrino latest data. Hence our model may be testable in the future neutrino experiments.

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arXiv2023

Neutrino Mixing Phenomenology: $A_4$ Discrete Flavor Symmetry with Type-I Seesaw Mechanism

We study a neutrino mass model with $A_4$ discrete flavor symmetry using a type-I seesaw mechanism. The inclusion of extra flavons in our model leads to the deviations from exact tribimaximal mixing pattern resulting in a nonzero $θ_{13}$ consistent with the recent experimental results and a sum rule for light neutrino masses is also obtained. In this framework, a connection is established among the neutrino mixing angles: reactor mixing angle($θ_{13}$), solar mixing angle($θ_{12}$) and atmospheric mixing angle ($θ_{23}$). This model also allows us a prediction of Dirac CP-phase and Jarlskog parameter $J$. The octant of the atmospheric mixing angle $θ_{23}$ occupies the lower octant. Our model prefers normal hierarchy (NH) than inverted hierarchy (IH). We use the parameter space of our model of neutrino masses to study the neutrinoless double beta decay parameter $m_{ee}$. Keywords: Discrete flavor symmetry, Type-I seesaw mechanism, Tribimaximal mixing, Dirac CP-phase, Jarlskog parameter, Neutrinoless double beta decay

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arXiv2023

A minimal inverse seesaw model with $S_4$ flavour symmetry

We construct an $S_4$ flavour symmetric minimal inverse seesaw model where the standard model is extended by adding two right-handed and two standard model gauge singlets neutrinos to explain the origin of tiny neutrino masses. The resulting model describes the lepton mass spectra and flavour mixing quite well for the case of the normal hierarchy of neutrino masses. The prediction of the model on the Dirac CP-violating phase is centered around $370.087^\circ$. Furthermore, using the allowed region for the model parameters, we have calculated the value of the effective Majorana neutrino mass, $\lvert\langle m_{ee}\rangle\rvert$, which characterizes neutrinoless double beta decay.

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arXiv2023

Non-zero $θ_{13}$, CP-violation and Neutrinoless Double Beta Decay for Neutrino Mixing in the $A_4\times Z_2\times Z_3$ Flavor Symmetry Model

We study the modification of the Altarelli-Feruglio $A_4$ flavor symmetry model by adding three singlet flavons $ξ'$, $ξ''$ and $ρ$ and the model is augmented with extra $Z_2\times Z_2^ \prime$ symmetry to prevent the unwanted terms in our study. The addition of these three flavons lead to two higher order corrections in the form of two perturbation parameters $ε$ and $ε^\prime$. These corrections yield the deviation from exact tri-bimaximal (TBM) neutrino mixing pattern by producing a non-zero $θ_{13}$ and other neutrino oscillation parameters which are consistent with the latest experimental data. In both the corrections, the neutrino masses are generated via Weinberg operator. The analysis of the perturbation parameters $ε$ and $ε^\prime$, shows that normal hierarchy (NH) and inverted hierarchy (IH) for $ε$ does not change much. However, as the values of $ε^\prime$ increases, $θ_{23}$ occupies the lower octant for NH case. We further investigate the neutrinoless double beta decay parmeter $m_{ββ}$ using the parameter space of the model for both normal and inverted hierarchies of neutrino masses.

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arXiv2022

Connecting low-energy CP violation, resonant leptogenesis and neutrinoless double beta decay in a radiative seesaw model

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.

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arXiv2021

Physics potentials with a combined sensitivity of T2K-II, NO$ν$A extension and JUNO

Leptonic \textit{CP} violation search, neutrino mass hierarchy determination, and the precision measurement of oscillation parameters for a unitary test of the leptonic mixing matrix are among the major targets of the ongoing and future neutrino oscillation experiments. The work explores the physics reach for these targets by around 2027, when the third generation of the neutrino experiments starts operation, with a combined sensitivity of three experiments: T2K-II, NO$ν$A extension, and JUNO. It is shown that a joint analysis of these three experiments can conclusively determine the neutrino mass hierarchy. Also, at certain values of \emph{true} \dcp, it provides closely around a $5σ$ confidence level (C.L.) to exclude \textit{CP}-conserving values and more than a $50\%$ fractional region of \emph{true} $δ_{\text{CP}}$ values can be explored with a statistic significance of at least a $3σ$ C.L. Besides, the joint analysis can provide unprecedented precision measurements of the atmospheric neutrino oscillation parameters and a great offer to solve the $θ_{23}$ octant degeneracy in the case of nonmaximal mixing.

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arXiv2021

Resonant leptogenesis and TM$_1$ mixing in minimal Type-I seesaw model with S$_4$ symmetry

We present an S$_4$ flavour symmetric model within a minimal seesaw framework resulting in mass matrices that leads to TM$_1$ mixing. Minimal seesaw is realized by adding two right-handed neutrinos to the Standard Model. The model predicts Normal Hierarchy (NH) for neutrino masses. Using the constrained six-dimensional parameter space, we have evaluated the effective Majorana neutrino mass, which is the parameter of interest in neutrinoless double beta decay experiments. The possibility of explaining baryogenesis via resonant leptogenesis is also examined within the model. A non-zero, resonantly enhanced CP asymmetry generated from the decay of right-handed neutrinos at the TeV scale is studied, considering flavour effects. The evolution of lepton asymmetry is discussed by solving the set of Boltzmann equations numerically and obtain the value of baryon asymmetry to be $\lvert η_B \rvert = 6.3 \times 10^{-10}$.

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arXiv2020

Charged Lepton Flavor Violation in SU(5) SUSY GUT and MSSM + Type-I Seesaw Model

Till today lepton flavor violation has not been observed in processes involving charged leptons. Hence, a search for it is under hot pursuit both in theories and experiments. In our current work, we investigate the rates of rare decay processes such as $τ\rightarrow μγ$ in SU(5) SUSY GUT and found that it satisfies the current bound and is one order below the projected sensitivity. This gives a corroborative argument for the influence of the large top-Yukawa coupling at the GUT scale ($λ_{tG}$) on flavor violating decay rates of leptons which are investigable at low energy electroweak scale $M_Z$. Secondly, we discuss the decay rates of $μ\rightarrow e γ$ & $τ\rightarrow μγ$ in MSSM with added right handed neutrino superfields. From this, we set bounds on $\tan β$ and further, we investigate the mass of $\tildeχ^0 _1$, the LSP, using the rates of LFV decays. In the calculations, the latest updated data from LHC, neutrino oscillation experiments and constraints on branching ratios from the MEG experiment have been used.

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arXiv2018

Detection techniques and investigation of different neutrino experiments

Neutrino physics is an experimentally driven field. So, we investigate the different detection techniques available in the literature and study the various neutrino oscillation experiments in a chronological manner. Our primary focus is on the construction and detection mechanisms of each experiment. Today, we know a lot about this mysterious ghostly particle by performing different experiments at different times with different neutrino sources viz. solar, atmospheric, reactor, accelerators and high energy astrophysical; and they have contributed in the determination of neutrino parameters. Yet the problems are far from over. We need to determine more precise values of the already known parameters and unravel the completely unknown parameters. Some of the unknowns are absolute masses of neutrino, types of neutrino, mass hierarchy, octant degeneracy and existence of leptonic CP Phase(s). We analyse the neutrino experiments into the past, present and the future (or proposed). We include SNO, Kamiokande, K2K, MINOS, MINOS+, Chooz, NEMO and ICARUS in the past; while Borexino, Double Chooz, Super-K, T2K, IceCube, KamLAND, NO$ν$A, RENO and Daya Bay in the present; and SNO+, Hyper-K, JUNO, RENO-50, INO, DUNE, SuperNEMO, KM3NeT, P2O, LBNO and PINGU in the proposed experiments. We also discuss the necessities of upgrading the present ones to those of the proposed ones thereby summarizing the potentials of the future experiments. We conclude this paper with the current status of the neutrinos.

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arXiv2017

The Effects of Majorana Phases in Estimating the Masses of Neutrinos

Majorana CP violating phases coming from heavy right-handed Majorana mass matrices ($M_{RR}$) are considered to estimate the masses of neutrinos.The effects of phases on quasi-degenerate neutrinos mass matrix obeying $μ$-$τ$ symmetry predicts the results consistent with observations for (i) solar mixing angle($θ_{12}$) below TBM, (ii) absolute neutrino mass parameters[$m_{ee}$] in neutrinoless double beta ($0νββ$) decay, and (iii) cosmological upper bound $\sum_{i}m_{i}$. Analysis is carried out through parameterization of light left-handed Majorana neutrino matrices $(m_{LL})$ using only two unknown parameters $(ε,η)$ within $μ$-$τ$ symmetry. We consider the charge lepton and up quark matrices as diagonal form of Dirac neutrino mass matrix $(m_{LR})$, and $m_{RR}$ are genrated using $m_{LL}$ through inversion of Type-I seesaw formula. The analysis shows that the masses of neutrinos are in agreement with the upper bound from cosmology and neutrinoless double beta decay. The results presented in this article will have important implications in discriminating the neutrinos mass models.

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arXiv2014

Baryon Asymmetry in Neutrino Mass Models with and without θ_13

We investigate the comparative studies of cosmological baryon asymmetry in different neutrino mass models with and without θ_13 by considering the three diagonal form of Dirac neutrino mass matrices, down-quark (4,2), up-quark (8,4) and charged lepton (6,2). The predictions of any models with θ_13 are consistent in all the three stages of leptogenesis calculations and the results are better than the predictions of any models without θ_13 which are consistent in a piecemeal manner with the observational data. For the best model, the normal hierarchy Type-IA for charged lepton (6,2) without θ_13, the predicted inflaton mass required to produce the observed baryon asymmetry is found to be 3.6x10 to the power 10 GeV corresponding to reheating temperature TR 4.5x10 to the power 6 GeV, while for the same model with θ_13, the inflaton mass is 2.24x10 to the power 11 GeV, TR 4.865x10 to the power 6 GeV and weak scale gravitino mass m(2 divided by 3) 100 GeV without causing the gravitino problem. These values apply to the recent discovery of Higgs boson of mass 125 GeV. The relic abundance of gravitino is proportional to the reheating temperature of the thermal bath. One can have the right order of relic dark matter abundance only if the reheating temperature is bounded to below 10 to the power 7 GeV.

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arXiv2012

Validity of quasi-degenerate neutrino mass models and their predictions on baryogenesis

Quasi-degenerate neutrino mass models (QDN) which can explain the current data on neutrino masses and mixings,are studied. In the first part, we study the effect of CP-phases on QDN mass matrix obeying $μ-τ$ symmetry in normal hierarchical (QD-NH) and inverted hierarchical (QD-IH) patterns.The numerical predictions are consistent with observed data on solar mixing angle, absolute neutrino mass parameter consistent with neutrinoless double beta decay mass parameter and sum of three absolute neutrino masses from cosmological bound.The neutrino mass matrix is parameterized using only two unknown parameters. The second part deals with the estimation of observed baryon asymmetry of the universe. The prediction is nearly consistent with observation with flavoured thermal leptogenesis scenario. QD-NH model appears to be more favourable than those of QD-IH models.The present analysis shows that the three absolute neutrino masses may exhibit quasi-degenerate pattern in nature. They are far from discrimination at the moment.

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arXiv2012

Quasi-Degenerate Neutrino Masses with Normal and Inverted Hierarchy

The effects of CP-phases on the three absolute quasi-degenerate Majorana neutrino (QDN) masses are stud-ied with neutrino mass matrices obeying μ - τ symmetry for normal as well as inverted hierarchical mass patterns. We have made further investigations on 1) the prediction of solar mixing angle which lies below tri-bimaximal mixing value in consistent with neutrino oscillation observational data, 2) the prediction on absolute neutrino mass parameter (mee) in 0νββ decay, and 3) cosmological bound on the sum of the three absolute neutrino masses. The numerical analysis is carried out through the parameterization of neu- trino mass matrices using only two unknown parameters (ε, η) within μ - τ symmetry. The results show the validity of QDN mass models in both normal and inverted hierarchical patterns. These models are far from discrimination and hence not yet ruled out. The results presented in this article are new and have subtle ef- fects in the discrimination of neutrino mass models.

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