arXiv subjects

Monal Kashav

Publications and source records attributed to Monal Kashav.

15 recordsLinked to original sources

arXiv2026

Dominant One-Loop Seesaw Contribution Induced by Non-Invertible Fusion Algebra

The topological classification of the one-loop Weinberg operator at dimension-5 enables a systematic categorization of radiative neutrino mass models. Among these, the category consisting loop-extended seesaw frameworks is theoretically appealing but conventional discrete or continuous symmetries (\emph{e.g.}, $U(1)$ or $\mathbb{Z}_M$) cannot genuinely forbid the corresponding tree-level contributions, making loop dominance difficult to realize. We show that \textit{non-invertible selection rules} (NISRs) naturally enforce the absence of tree-level terms while ensuring a dominant one-loop contribution. Intriguingly, the same non-invertible structure also stabilizes the dark matter candidate, providing a unified radiative origin of neutrino mass and dark sector stability. In particular, we focus on the T4-2-$i$ topology which embodies a type-II one-loop seesaw and demonstrate its natural realization from $Z_{7}$ Tambara--Yamagami (TY) fusion algebra.

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arXiv2026

Testing residual-symmetry-fixed columns of $U_{\rm PMNS}$ at DUNE and T2HK with initial JUNO constraints

We study fixed-column predictions of the lepton mixing matrix that arise from residual symmetries originating in a class of discrete flavour and modular symmetries. While the recent high-precision determination of $\sin^{2}\theta_{12}$ by JUNO already constrains part of these predictions, the remaining ones are primarily characterized by non-trivial correlations between $\sin^{2}\theta_{23}$ and the Dirac CP phase $\delta_{\rm CP}$, which are currently only weakly constrained. This motivates a detailed investigation using next-generation long-baseline neutrino experiments. For the viable scenarios, we derive precise $\sin^{2}\theta_{23}$-$\delta_{\rm CP}$ correlations and use them to generate test-event samples, marginalising over the remaining oscillation parameters. We perform detailed simulations for DUNE and T2HK, presenting allowed regions in the $\sin^{2}\theta_{23}$-$\delta_{\rm CP}$ plane and evaluating the CP-violation fraction as a function of exposure. Our results show that the combined sensitivity of DUNE and T2HK provides a robust test of fixed-column lepton-mixing predictions.

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arXiv2024

Residual flavour (anti)symmetries at the modular self-dual point and constraints on neutrino masses and mixing

We explore the implications of symmetries that remain unbroken at the self-dual point $\tau=i$ in modular invariant theories. Assuming that (a) the three generations of lepton doublets transform as an irreducible representation of a finite modular group $\Gamma_N$, and (b) the light neutrino masses arise from the Weinberg operator and are in modular form, we demonstrate that this setup yields a unique residual flavor symmetry or antisymmetry for the neutrinos, depending on the modular weight. In the antisymmetric case, one neutrino is always massless, and the other two can be degenerate if the mass matrix is real. These findings are independent of the level $N$. If the charged leptons are arranged to exhibit an appropriate residual symmetry from the same $\Gamma_N$, they determine a column of the leptonic mixing matrix, leading to specific correlations between the mixing angles and the Dirac CP phase. The presence of residual (anti)symmetries enables the application of standard flavor symmetry techniques to derive these predictions, and we scan all possible $\Gamma_N$ satisfying condition (a). Most solutions yield ${\cal O}(1)$ entries in the fixed column, favouring relatively large lepton mixing.

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arXiv2024

Minimal Type-I Dirac seesaw and Leptogenesis under $A_{4}$ modular invariance

We present a Dirac mass model based on $A_{4}$ modular symmetry within Type-I seesaw framework. This extension of Standard Model requires three right-handed neutrinos and three heavy Dirac fermions superfields, all singlet under $SU(2)_{L}$ symmetry. The scalar sector is extended by the inclusion of a $SU(2)_{L}$ singlet superfield, $\chi$. Here, the modular symmetry plays a crucial role as the Yukawa couplings acquire modular forms, which are expressed in terms of Dedekind eta function $\eta(\tau)$. Therefore, the Yukawa couplings follow transformations akin to other matter fields, thereby obviating the necessity of additional flavon fields. The acquisition of $vev$ by complex modulus $\tau$ leads to the breaking of $A_{4}$ modular symmetry. We have obtained predictions on neutrino oscillation parameters, for example, the normal hierarchy for the neutrino mass spectrum. Furthermore, we find that heavy Dirac fermions, in our model, can decay to produce observed baryon asymmetry of the Universe through Dirac leptogenesis.

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arXiv2023

Trimaximal Mixing and Extended Magic Symmetry in a Model of Neutrino Mass Matrix

The trimaximal mixing scheme (TM$_2$) results in \textit{``magic"} neutrino mass matrix ($M_ν$) which is known to accommodate neutrino oscillation data. In this paper, we propose a phenomenological ansatz for $M_ν$ by extending the magic symmetry that leads to further reduction in the number of free parameters, thereby, increasing the predictability of the model. The neutrino mixing parameters, effective Majorana mass $m_{ee}$ and $CP$ invariants ($J_{CP}, I_1,I_2$) are found to exhibit strong correlations for TM$_2$ mixing paradigm. One of the generic feature of the model is the requirement of non-maximal $θ_{23}$ for possible $CP$ violation measurable in neutrino oscillation experiments. The observables $m_{ee}$ and sum of neutrino masses ($\sum m_i$) have imperative implications for yet unknown neutrino mass hierarchy. For inverted hierarchy, the lower bound on $m_{ee}>0.02$ eV, predicted by the model, is found to be within the sensitivity reach of the $0νββ$ decay experiments. Also, cosmological bound of $0.12$ eV on $\sum m_i$, at 95\% CL, refutes inverted hierarchy implying TM$_2$ with normal hierarchy as the only viable possibility in the model. We have, also, illustrated a scenario wherein such a construction of the neutrino mass matrix can be realized using $Δ(54)$ symmetry in the framework of Type-I+II seesaw mechanism.

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arXiv2023

On Minimal realization of Topological Lorentz Structures with one-loop Seesaw extensions in A$_4$ Modular Symmetry

The topological classification of one-loop Weinberg operator at dimension-5 leads to systematic categorization of one-loop neutrino mass models. All one-loop neutrino mass models must fall in one of these categories. Among these topological categories, loop extension of canonical seesaw scenarios is interesting in light of the current LHC run. Apart from one-loop contribution, these extensions result in dominant tree-level contribution to neutrino masses. The immediate remedy to obtain dominant one-loop contribution requires combination of flavor symmetries and enlarged field content. Alternatively, in this work, we propose a minimal way of realizing the topological structures with dominant one-loop contribution using modular variant of the permutation symmetries. In such a realization, no new fields are needed apart from those permitted by the topology itself. For the first time, we have realized one such topological Lorentz structure(T4-2-$i$) pertaining to one-loop extension of Type-II seesaw using modular A$_4$ symmetry. Here, modular weights play an important role in suppressing tree-level terms and stabilizing the particles running in the loop($N_i$, $ρ$ and $ϕ$), thus, making them suitable dark matter candidates. In this work, we have explored the possibility of fermionic dark matter candidate where right-handed neutrino ($N_1$) is assumed to be lightest. We have, also, analyzed the compatibility of the model with neutrino oscillation data and obtained model predictions for effective Majorana mass $M_{ee}$ and $CP$ violation. Furthermore, the predictions on relic density of dark matter and its direct detection considering bound on lepton flavor violating process, $μ\rightarrow eγ$ have, also, been investigated.

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arXiv2022

Investigating Two-zero Textures of Inverse Neutrino Mass Matrix under the Lamp Post of LMA and LMA-D Solutions and Symmetry Realization

In this work we have investigated the phenomenological consequences of two-zero textures of \textit{inverse} neutrino mass matrix ($M_ν^{-1}$) in light of the large mixing angle (LMA) and large mixing angle-\textit{dark} (LMA-D) solutions, later of which originates if neutrinos exhibit non-standard interactions with matter. Out of fifteen possibilities, only seven two-zero textures of $M_ν^{-1}$ are found to be phenomenologically allowed under LMA and/or LMA-D descriptions. In particular, five textures are in consonance with both LMA and LMA-D solutions and are necessarily $CP$ violating while remaining two textures are found to be consistent with LMA solution only. The textures with vanishing (1, 1) element of $M_ν^{-1}$ are, in general, disallowed. All the textures allowed under LMA and LMA-D solutions follow the same neutrino mass hierarchy. Furthermore, textures with vanishing (2, 3) element of $M_ν^{-1}$ are found to be either disallowed or are consistent with LMA description only. We have, also, obtained the implication of the model for $0νββ$ decay amplitude $|M_{ee}|$. For most of the textures the calculated $3σ$ lower bound on $|M_{ee}|$ is $\mathcal{O}(10^{-2})$, which is within the sensitivity reach of $0νββ$ decay experiments. We have, also, proposed a flavor model based on discrete non-Abelian flavor group $A_4$ wherein such textures of $M_ν^{-1}$ can be realized within Type-I seesaw setting.

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arXiv2022

Muon ($g-2$) and W-boson mass Anomaly in a Model Based on $Z_4$ Symmetry with Vector like Fermion

The latest results of CDF-II collaboration show a discrepancy of $7σ$ with standard model expectations. There is, also, a $4.2σ$ discrepancy in the measurement of muon magnetic moment reported by Fermilab. We study the connection between neutrino masses, dark matter, muon ($g-2$) and W-boson mass anomaly within a single coherent framework based on $Z_{4}$ extension of the scotogenic model with vector like lepton (VLL). Neutrino masses are generated at one loop level. The inert doublet, also, provide a solution to W-boson mass anomaly through correction in oblique parameters $S$, $T$ and $U$. The coupling of VLL triplet $ψ_T$ to inert doublet $η$ provides positive contribution to muon anomalous magnetic moment. In the model, the VLL triplet provides a lepton portal to dark matter ($η_R^0$). The model predicts a lower bound $m_{ee}>0.025$ eV at 3$σ$, which is well within the sensitivity reach of the $0νββ$ decay experiments. The model explains muon anomalous magnetic moment $Δa_μ$ for $1.3<y_ψ<2.8$ and mass of DM candidate in the range $152\text{ GeV}<M_{η_{R}^{0}}<195\text{ GeV}$. The explanation of W-boson mass anomaly, further, constrain the mass of DM candidate, $M_{η_{R}^{0}}$, in the range $154\text{ GeV}<M_{η_{R}^{0}}<174\text{ GeV}$.

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arXiv2022

Gauged $U(1)_{L_μ-L_τ}$ Symmetry and two-zero Textures of Inverse Neutrino Mass Matrix in light of Muon ($g-2$)

In the framework of anomaly free $U(1)_{L_μ-L_τ}$ model, charged scalar fields give rise to massive gauge boson ($Z_{μτ}$) through spontaneous symmetry breaking. $Z_{μτ}$ leads to one loop contribution to the muon anomalous magnetic moment. These scalar fields may, also, appear in the structure of right-handed neutrino mass matrix, thus, connecting the possible explanation of muon ($g-2$) and low energy neutrino phenomenology through $vevs$ associated with the scalar fields. In the present work, we consider textures of inverse neutrino mass matrix ($M_ν^{-1}$) wherein any two elements of the mass matrix are zero. In this ansatz, with Dirac neutrino mass matrix diagonal, the zero(s) of right-handed Majorana neutrino mass matrix correspond to zero(s) in the low energy effective neutrino mass matrix (within Type-I seesaw). We have realized two such textures of $M_ν^{-1}$ accommodating the muon ($g-2$) and low energy neutrino phenomenology. The requirement of successful explanation of muon ($g-2$), further, constrain the allowed parameter space of the model and results in sharp correlations amongst neutrino mixing angles, $CP$ invariants and effective Majorana mass ($M_{ee}$). The model explains muon ($g-2$) for $M_{Z_{μτ}}$ in the range ($0.035$ GeV-$0.100$ GeV) and $g_{μτ}\approx\mathcal{O}(10^{-4}$) which is found to be consistent with constraints coming from the experiments like CCFR, COHERENT, BABAR, NA62 and NA64.

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arXiv2022

Muon ($g-2$) in $U(1)_{L_μ-L_τ}$ Scotogenic Model Extended with Vector like Fermion

The latest results of anomalous muon magnetic moment at Fermilab show a discrepancy of 4.2 $σ$ between the Standard Model (SM) prediction and experimental value. In this work, we revisit $U(1)_{L_μ-L_τ}$ symmetry with in the paradigm of scotogenic model which explains muon ($g-2$) and neutrino mass generation, simultaneously. The mass of new gauge boson $M_{Z_{μτ}}$ generated after the spontaneous symmetry breaking of $U(1)_{L_μ-L_τ}$ is constrained, solely, in light of the current neutrino oscillation data to explain muon ($g-2$). In particular, we have obtained two regions I and II, around 150 MeV and 500 MeV, respectively, in $M_{Z_{μτ}}-g_{μτ}$ plane which explain the neutrino phenomenology. Region I is found to be consistent with muon neutrino trident (MNT) bound ($g_{μτ}$ $\leq$ $10^{-3}$) to explain muon ($g-2$), however, region II violates it for mass range $M_{Z_{μτ}}>300$ MeV. We, then, extend the minimal gauged scotogenic model by a vector like lepton (VLL) triplet $ψ_T$. The mixing of $ψ_T$ with inert scalar doublet $η$ leads to chirally enhanced positive contribution to muon anomalous magnetic moment independent of $Z_{μτ}$ mass. Furthermore, we have, also, investigated the implication of the model for $0νββ$ decay and $CP$ violation. The non-observation of $0νββ$ decay down to the sensitivity of 0.01 eV shall refute the model. The model, in general,is found to be consistent with both $CP$ conserving and $CP$ violating solutions.

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arXiv2021

Scalar Dark Matter in $A_4$ based texture one-zero neutrino mass model within Inverse Seesaw Mechanism

In this paper, we present a model based on $A_4$ discrete flavor symmetry implementing inverse and type-II seesaw mechanisms to have LHC accessible TeV scale right-handed neutrino mass and texture one-zero in the resulting Majorana neutrino mass matrix, respectively. We investigate neutrino and dark matter sectors of the model. Non-Abelian discrete $A_{4}$ symmetry spontaneously breaks into $Z_{2}$ subgroup and hence provide stable dark matter candidate. To constrain the Yukawa Lagrangian of our model, we imposed $Z'_2$, $Z_3$ and $Z_4$ cyclic symmetries in addition to the $A_4$ flavor symmetry. In this work we used the recently updated data on cosmological parameters from PLANCK 2018. For the dark matter candidate mass around 45 GeV-55 GeV, we obtain the mediator particle mass(right-handed neutrinos) ranging from 138 GeV to 155 GeV. The Yukawa couplings is found to be in the range 0.995-1 to have observed relic abundance of dark matter. We, further, obtain inverse ($X\equiv\frac{F^2n}{z^2}$) and type-II ($X^{'}\equiv f_1 v_{Δ_{1}}$) seesaw contributions to $0νββ$ decay amplitude $|M_{ee}|$, while model being consistent with low energy experimental constraints. In particular, we emphasize that type-II seesaw contribution to $|M_{ee}|$ is large as compared to inverse seesaw contribution for normally ordered(NO) neutrino masses.

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arXiv2021

Scotogenesis in Hybrid Textures of Neutrino Mass Matrix and Neutrinoless Double Beta Decay

We study the connection between dark matter (DM) and neutrinoless double beta ($0νββ$) decay in a scotogenic model with hybrid texture in the neutrino mass matrix. Characteristically, the framework allows to write all the non-zero elements of the mass matrix proportional to effective Majorana mass $\left|M_{ee}\right|$. The overall scale of the neutrino mass is found to be governed by non-zero $\left|M_{ee}\right|$. We have obtained interesting correlations of relic density of DM($Ωh^2$) with DM mass $M_1$ and $\left|M_{ee}\right|$. Using experimental value of DM relic density($Ωh^2$), the DM mass $M_1$, is found to be $\mathcal{O}$(1TeV) which is within reach of collider experiments. Specifically, for all five hybrid textures, the range of upper bound on DM mass $M_1$ is found to be ($2.27$-$5.31$)TeV. Another interesting feature of the model is the existence of lower bound on $|M_{ee}|$ for all allowed hybrid textures except texture $T_5$ which can be probed in current and future $0νββ$ decay experiments. With high sensitivities, these experiments shall establish the theoretical status of the proposed model. For example, the non-observation of $0νββ$ decay down to the sensitivity $\mathcal{O}(0.03)$eV will refute $T_3$ hybrid texture.

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arXiv2021

Broken Scaling Neutrino Mass Matrix and Leptogenesis based on A$_4$ Modular invariance

In this work, we have proposed a modular $A_4$ symmetric model of neutrino mass which, simultaneously, explains observed baryon asymmetry of the Universe(BAU). In minimal extension of the standard model(SM) with two right-handed neutrinos we work in a supersymmetric framework. At Type-I seesaw level, the model predicts scaling in the neutrino mass matrix. In order to have correct low energy phenomenology, we propose two possible scenarios of scale-breaking in the neutrino mass matrix emanating from Type-I seesaw. Scenario-1 is based on the dimension-5 Weinberg operator whereas scenario-2 implements Type-II seesaw via scalar triplet Higgs superfields($Δ,\barΔ$). Interestingly, the breaking patterns in both, otherwise dynamically different scenarios, are similar which can be attributed to the same charge assignments of superfields($Δ,\barΔ$) and the Higgs superfield $H_u$ under modular $A_4$ symmetry. The breaking is found to be proportional to the Yukawa coupling of modular weight 10($Y_{1,1'}^{10}$). We, further, investigates the predictions of the model under scenario-2 (Type-I+II) for neutrino mass, mixings and matter-antimatter asymmetry of the Universe. The model predicts normal hierarchical neutrino masses and provide a robust range ($0.05-0.08$)eV for sum of neutrino masses($\sum m_{i}$). Lepton number violating $0νββ$ decay amplitude($M_{ee}$) is obtained to lie in the range ($0.04-0.06$)eV. Future $0νββ$ decay experiments such as NEXT and nEXO shall pose crucial test for the model. Both $CP$ conserving and $CP$ violating solutions are allowed in the model. Interesting correlations are obtained, specially, between Yukawa couplings of modular weight 2 and complex modulus $τ$. The model exhibit consistent explanation of BAU for right-handed Majorana neutrino mass scale in the range ($(1-5)\times10^{13}$)GeV.

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arXiv2020

Magic neutrino mass model with broken $μ-τ$ symmetry and Leptogenesis

We investigate baryogenesis via leptogenesis in $A_4$ flavor model within the paradigm of type-I and II seesaw mechanism resulting in magic neutrino mass matrix with broken $μ-τ$ symmetry in a minimal scenario with two right-handed neutrinos(2RHN). Additional $Z_3$ cyclic symmetry is employed to constrain the Yukawa structure of model. The type-II seesaw terms play crucial role in generating non-degenerate neutrino masses and non-zero $θ_{13}$ and contribute in baryogenesis. In particular, after the spontaneous symmetry breaking, the Yukawa couplings $y_{Δ_1}$ and $y_{Δ_3}$ are responsible for the breaking of $μ-τ$ symmetry. The effective Majorana neutrino mass $|M_{ee}|$ is found to be well within the sensitivity reach of the $0νββ$ experiments, in particular, for inverted hierarchy. The model has imperative implication for inverted hierarchy, for example, the non-observation of this process at nEXO will rule out IH. The predicted baryon asymmetry is in good agreement with the observed baryon asymmetry for NH whereas IH is disallowed at 2.5$σ$ C.L..

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arXiv2019

Highly predictive and testable $A_{4}$ flavor model within type-I and II seesaw framework and associated phenomenology

We investigate neutrino mass model based on $A_4$ discrete flavor symmetry in type-I+II seesaw framework. The model has imperative predictions for neutrino masses, mixing and $CP$ violation testable in the current and upcoming neutrino oscillation experiments. The important predictions of the model are: normal hierarchy for neutrino masses, a higher octant for atmospheric angle ($θ_{23}>45^{o}$) and near-maximal Dirac-type $CP$ phase ($δ\approxπ/2$ or $3π/2$) at $3σ$ C. L.. These predictions are in consonance with the latest global-fit and results from Super-Kamiokande(SK), NO$ν$A and T2K. Also, one of the important feature of the model is the existence of a lower bound on effective Majorana mass, $|M_{ee}|\geq 0.047$eV(at 3$σ$) which corresponds to the lower part of the degenerate spectrum and is within the sensitivity reach of the neutrinoless double beta decay(0$νββ$) experiments.

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