arXiv subjects

Maibam Ricky Devi

Publications and source records attributed to Maibam Ricky Devi.

10 recordsLinked to original sources

arXiv2026

A Rotational Perturbative Correction to Democratic Neutrino Mixing and JUNO Compatibility

In this work, we revamp the democratic mixing matrix (DM) by adding a perturbation term such that the mixing angles derived from it are compatible with the NuFIT 6.1 and recent findings from the Jiangmen Underground Neutrino Observatory (JUNO). To do this, we have incorporated perturbation term in the elements of the mixing matrix such that it does not lose its unitarity. Thus, the democratic mixing matrix, once ruled out by the experimental evidences from T2K, Double Chooz, and Daya Bay, can be modified with rotational perturbation in the (1,2), (1,3), and (2,3) sectors and additional real parameters added in each element of DM. Finally, we analyze the allowed and disallowed textures in light of the JUNO findings.

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arXiv2025

An $A_4$-Symmetric Double Seesaw for Neutrino Masses and Mixing in Light of JUNO results

We discuss a double seesaw mechanism for generating light neutrino masses within the Standard Model extensions that include both right-handed neutrinos and extra gauge-singlet sterile fermions. The flavour structure of the double seesaw framework is invoked by an $A_4$ discrete symmetry which yields predictive textures for the Dirac neutrino mass matrix $M_D$, the mixing matrix $M_{RS}$ connecting right-handed and sterile neutrinos, and the bare Majorana mass matrix $M_S$ for the sterile neutrinos. The interesting feature of the present framework is that the combination of the double seesaw mechanism and $A_4$ flavour alignments yields a leading-order TBM structure, corrected by a single rotation in the (1-3) sector. We also derive analytic expressions for the heavy sterile eigenvalues and for the resulting light neutrino masses, thereby clarifying the role of the symmetry in shaping the neutrino mass hierarchy. We further incorporate the most recent JUNO measurements, which improve the precision of the solar mixing angle $\sin^2\theta_{12} \simeq 0.31$, along with updated constraints on $\sin^2\theta_{13}$. We show that these results significantly restrict the allowed parameter space of the model. In particular, the observed value of $\sin^2\theta_{12}$ constrains the magnitude of the (1--3) rotation and the phases associated with the $A_4$ flavon couplings, while the value of $\sin^2\theta_{13}$ sharpens these restrictions further. Overall, the interplay between double seesaw dynamics, $A_4$ flavour symmetry, and the recent JUNO constraints yields a highly predictive framework for neutrino masses and mixings, offering a coherent explanation for the generation of light neutrino masses and testable predictions for future experiments.

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arXiv2025

Non-Holomorphic $A_4$ Modular Symmetry in Type-I Seesaw: Implications for Neutrino Masses and Leptogenesis

We propose a minimal extension of the Standard Model with right-handed neutrinos, governed by a non-holomorphic $A_{4}$ modular flavor symmetry. Within this model framework, the light neutrino masses are generated via the popular type-I seesaw mechanism in which the structure of the Dirac neutrino Yukawa couplings is decided by nonholomorphic modular forms. Unlike conventional flavor models with ad hoc flavon fields, the structure of Dirac and Majorana mass matrices is entirely determined by a modulus parameter $\tau$. We construct the predictive mass matrices for charged leptons, Dirac neutrinos, and right-handed Majorana neutrinos and show the compatibility with neutrino oscillation data by an appropriate choice of input model parameters. We present numerical analysis of two sets of benchmark points explaining neutrino masses while generating the correct amount of baryon asymmetry via thermal leptogenesis. We estimate numerically the values of CP-asymmetry and examine the evolution of the lepton asymmetry by studying Boltzman equations by considering both strong and washout regimes with CP-asymmetry parameter in the range $|\varepsilon_{1}| \sim 10^{-4}$--$10^{-8}$. The model predicts an effective Majorana mass in the few meV range, below current experimental bounds but within reach of next-generation $0\nu\beta\beta$ searches. The key feature of non-holomorphic $A_4$ modular symmetry naturally accommodates non-zero neutrino masses and mixings, minimizes the Yukawa arbitrariness, and establishes a direct connection between high-scale leptogenesis with low-energy neutrino observable parameters, thereby the model provides a testable link between neutrino flavor physics and cosmology.

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arXiv2024

Neutrino Masses and Higher Degree Siegel Modular Forms

In this work, we have analyzed a neutrino model within the distinct framework of modular forms with degree, $ g>1 $ . This offers a more generalized scenario of modular forms which is popularly known as Siegel modular forms. We explore the implications of this special case of automorphic forms for physics beyond the standard model (BSM) within the lepton sector. In our model, we explicitly treat the Yukawa couplings as Siegel modular forms with both degree and level being equivalent to 2. We restrict our modulus parameter for $ τ_{1}=τ_{2} $ spanning within the finite modular $ S_{4}\times Z_{2} $ space. This helps us for a broader understanding of the multiplets at higher degree and simplifies the process of model building of the fermion masses. At the end, we compute the unknown neutrino oscillation parameters and find the optimal values of the modulus parameters $ τ_{1} $ and $ τ_{3} $ for which the values of the Yukawa couplings are consistent at $ 3σ$ for the input parameters of neutrinos as given in NuFIT 5.2 and discuss its underlying physics.

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arXiv2023

Linking resonant leptogenesis with dynamics of the inverse seesaw theory with $ A_{4} $ flavor symmetry

In this paper, we analyse resonant leptogenesis in a low scale inverse seesaw model with $A_4$ flavor symmetry, in a model we explored earlier to explain light neutrino masses and mixings, and also charged lepton flavor violating decay $μ\rightarrow eγ$. Six $ A_{4} $ scalar singlets and one $ A_{4} $ fermion triplet are included, which are charged under the group $A_{4}\times U(1)_{X} \times Z_{5} \times Z_{4} $, with at least two degenerate RH (Right Handed) neutrinos. The light neutrino masses and leptogenesis both share a same origin with the heavy right handed neutrinos. Thus, we expound the possibility of generating resonant leptogenesis in this model at energies as low as 1 TeV. We then analyse our findings to envision if our model inclines more towards weak or strong washout.

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arXiv2023

Retrieving texture zeros in 3+1 active-sterile neutrino framework under the action of $A_4$ modular-invariants

The flavour problem and the viability of texture zeros of the Majorana mass matrix in the 3+1 active-sterile neutrino mixing scenario are investigated in this work using a novel bottom-up technique where we leverage the pertinent concepts of full modular group, modular invariants, and $A_4$ flavour symmetry as theoretical tools for the explicit construction of neutrino models. In this approach we treat each chiral field as modular forms in the 3+1 neutrino mixing which are constrained by the $A_4$ modular symmetry. Using these techniques, we create straightforward predictive models that only depends on a few parameters and simultaneously explains the observed pattern of neutrino mixing without the need for fine-tuning, allowing us to perceive the feasible zero textures of the Majorana mass matrix under the 3+1 framework.We discuss the implications of the allowed 3+1 zero textures by analyzing the sterile neutrino parameters, providing insight into the flavor problem and the viability of the Majorana mass matrix. The values of the active-sterile mixing (ASM) parameters predicted from our models are highly consistent with the $3σ$ values of the ASM parameters.

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arXiv2023

Exploring the feasibility of the charged lepton flavor violating decay $ μ\rightarrow e + γ$ in inverse and linear seesaw mechanisms with $A_4$ flavour symmetry

One of the possible ways to explain the observed flavour structure of fundamental particles is to include flavor symmetries in the theories. In this work, we investigate the rare charged lepton flavour violating (cLFV) decay process ($μ\rightarrow eγ$) in two of the low scale ($\sim$TeV) seesaw models: (i) the Inverse seesaw (ISS) and (ii) Linear seesaw (LSS) models within the framework of $A_{4}$ flavour symmetry. Apart from the $ A_{4} $ flavour symmetry, some other symmetries like $U(1)_{X}$, $Z_4$ and $Z_5$ are included to construct the Lagrangian. We use results from our previous work \cite{Devi:2021ujp,Devi:2021aaz} where we computed unknown neutrino oscillation parameters within $3 σ$ limits of their global best fit values, and apply those results to compute the branching ratio (BR) of the muon decay for both the seesaw models. Next we compare our results with the current experimental bounds and sensitivity limits of BR($μ\rightarrow eγ$) as projected by various experiments, and present a comparative analysis that which of the two models is more likely to be tested by which current/future experiment. This is done for various values of currently allowed non-unitarity parameter. This comparative study will help us to pinpoint that which of the low scale seesaw models and triplet flavon VEV alignments will be more viable and favourable for testing under a common flavour symmetry ($A_{4}$ here), and hence can help discriminate between the two models.

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arXiv2022

Exploring dynamics of $A_4$ flavour symmetry using low scale seesaw mechanisms

Low scale seesaw models, like low scale type II, inverse (ISS), and linear seesaw (LSS) models provide an interesting mechanism to obtain light neutrino masses and mixings, as they can be tested in future TeV scale experiments. Discrete flavour symmetry groups like $A_4$ can be incorporated to explain the flavour structure of particles. But, so far, nothing is known about dynamics of flavour symmetry - scale of its breaking, or VEV alignment of the flavon fields. In a recent study [1], we have investigated and shed light on how to pinpoint the favoured VEV alignment of the flavon field using light neutrino oscillation data. In this work, for the first time, we present an analysis on dependence of light neutrino masses on scale of flavon VEV in these three seesaw models, and comment on how this information can be used to discriminate among them. We also discuss about the estimated value of the constant $F$ which can constrain various coupling constants of the model, cut-off scale of the theory and scale of flavour symmetry breaking. This study can provide useful insight into the hitherto unknown dynamics of flavour symmetry and hence can contribute as an important ingredient in the model building for future studies.

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arXiv2022

Octant of $θ_{23}$, MH, $0νββ$ decay and vacuum alignment of $ A_{4} $ flavour symmetry in an inverse seesaw model

Measurements of disappearance channel of long baseline accelerator based experiments (like NO$ν$A) are inflicted with the problem of octant degeneracy. In these experiments, the mass hierarchy (MH) sensitivity depends upon the value of CP-violating phase $δ_{CP}$. Moreover, MH of light neutrino masses is still not fixed. Also, the flavour structure of fermions is yet not fully understood. We discuss all these issues, in a highly predictive, low-scale inverse seesaw (ISS) model within the framework of $A_4$ flavour symmetry. Recent global analysis has shown a preference for normal hierarchy and higher octant of $θ_{23}$, and hence we discuss our results with reference to these, and find that the vacuum alignment of $A_4$ triplet flavon (1,-1,-1) favours these results. Finally, we check if our very precise prediction on $m_{ee}$ and the lightest neutrino mass falls within the range of sensitivities of the neutrinoless double beta decay ($0νββ$) experiments. We note that when octant of $θ_{23}$ and MH is fixed by more precise measurements of future experiments, then through our results, it would be possible to precisely identify the favourable vacuum alignment corresponding to the $A_{4}$ triplet field as predicted in our model.

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arXiv2021

A comparative study of type-II, inverse and linear seesaw mechanisms with $ A_{4} $ flavour symmetry

We present a comparative analysis of neutrino models based on a broad class of low scale seesaw mechanisms, viz., type II, inverse (ISS) and linear seesaw (LSS) mechanisms that are used to realize the tiny masses of neutrino. In particular, we present their lagrangians with respective particle content. We incorporate $ A_{4} $ flavour symmetry into our models to investigate the light neutrino masses and mixings and flavour structure as well. Apart from it, symmetries like $U(1)_{X}$, $Z_4$ and $Z_5$ to make the models viable are also used. Recent global fit values of neutrino oscillation parameters are used to find the unknown neutrino oscillation parameters such as the lightest neutrino mass and CPV phases (Dirac and Majorana). These unknown parameters can be found by solving a set of simultaneous equations obtained by using $ A_{4} $ product rules in the Lagrangian for different VEV alignments of the triplet flavon field. Finally these data of unknown neutrino oscillation parameters are used to study cLFV (Charged lepton flavour violation) decay $μ\rightarrow e+γ$ and is constrained using their latest bounds and sensitivities. Though we have constructed the models for all type II, ISS and LSS models for the sake of comparison, we focus on computation in LSS in this work. Computations are done up to the tolerance level $<10^{-5}$.

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