arXiv subjects

N. Nimai Singh

Publications and source records attributed to N. Nimai Singh.

At least 19 recordsLinked to original sources

arXiv2025

3+1 neutrino mixings model with $A_4$ triplet Majorana neutrino

We study a 3+1 active-sterile neutrino mixings model using an $A_4$ triplet right-handed neutrino $ν_R$ and a singlet eV-scale sterile neutrino under $A_4\times Z_3 \times Z_2$ discrete symmetry. Four scalar flavons are considered to reproduce neutrino oscillation parameters within the experimental 3$σ$ range. The model also studies the effective mass parameter in neutrinoless double beta decay experiments. Deviation from $μ-τ$ symmetry in the active neutrino mass matrix is generated through an antisymmetric interaction of $ν_R$. This model successfully explains active-sterile neutrino mixings consistent with the cosmological upper bound on the sum of active neutrino mass $\sum m_i < 0.113$ eV (0.145 eV) in NH(IH).

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arXiv2025

$A_{5}$ symmetry and deviation from Golden Ratio mixing with charged lepton flavor violation

A neutrino mass model that can satisfy the exact golden ratio mixing is constructed using $A_{5}$ discrete symmetry group. The deviation from the golden ratio mixing is studied by considering the contribution from the charged lepton sector in a linear seesaw framework. A definite pattern of charged lepton mass matrix predicted by the model controls the leptonic mixing angles. By taking the observed $θ_{13}$ as the input value, we can obtain the values of all the mixing angles and Dirac CP-violating phase within the current experimental bounds. The model predicts that only the normal neutrino mass ordering is consistent with the current oscillation data. We also study the two body charged lepton flavor violation (cLFV) processes such as $μ\rightarrow e +γ$, $τ\rightarrow e +γ$ and $τ\rightarrow μ+ γ$ and neutrinoless double beta decay parameter $m_{ββ}$. The present neutrino mass model can explain the current and future sensitivity of $μ\rightarrow e +γ$, $τ\rightarrow e+ γ$ processes and the present sensitivity of neutrinoless double beta decay parameter when the masses of quasi-Dirac neutrinos are in the TeV range. On the other hand, the model cannot reproduce the present sensitivity of $τ\rightarrow μ+ γ$ but can explain the future sensitivity and the present sensitivity of neutrinoless double beta decay parameter simultaneously when the masses of the quasi-Dirac neutrinos are in the TeV range.

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arXiv2024

Exploring active-sterile neutrino mixings models in MES mechanism using modular $S_3$ symmetry

We study the minimal extended seesaw mechanism with one sterile neutrino in a 3+1 framework using modular $S_3$ symmetry. The active-sterile neutrino models are classified based on the assignments of $S_3$ representations and modular weights of the left-handed lepton doublets, triplet right-handed neutrino, and sterile neutrino. No scalar flavons are considered, and the flavor symmetry is broken by the vacuum expectation value (vev) of the modulus $τ$. For a particular set of representations of the Leptons and Higgs field, we obtain eleven (11) different models based on different modular weights of charged lepton $(k_L)$ and right-handed neutrino ($k_N$). Out of these, we consider two models, which are discriminated by carrying out the numerical analysis so that the parameter space in each model can fit the latest neutrino oscillation data at 3$σ$. The Planck cosmological bound on the upper limit of the sum of the active neutrino masses $\sum m_i <0.12$eV is also considered. Finally, the best-fit parameters of the neutrino observables and model predictions are evaluated using the minimum $χ^2$ analysis.

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arXiv2024

Modular $A_4$ symmetry in 3+1 active-sterile neutrino masses and mixings

Motivated by the significance of modular symmetry in generating neutrino masses and flavor mixings, we apply the modular $A_4$ symmetry in a 3+1 scheme of active-sterile neutrino mixings. Neutrino oscillation observables in the 3$σ$ range are successfully reproduced through the vacuum expectation value of the modulus $τ$. We also study phenomenologies related to the effective neutrino masses $m_β$ in tritium beta decay and $m_{ββ}$ in neutrinoless double beta decay. Mixings between active neutrinos and eV scale sterile neutrino are analyzed in detail. The model also predicts the Dirac CP-violating phase $δ_{CP}$ and Majonara phases $α$ and $β$. The best-fit values of the neutrino mixing angles and ratios of two mass-squared differences are determined using minimum $χ^2$ analysis. The best-fit values of the neutrino oscillation observables are predicted as $\sin^2θ_{23}=0.573,$ $\sin^2θ_{12}=0.300,$ $ \sin^2θ_{13}=0.022$ and $r = 0.172$ for NH while $\sin^2θ_{23}=0.550,$ $\sin^2θ_{12}=0.303,$ $ \sin^2θ_{13}=0.022$ and $r = 0.171$ for IH. We also observe that the predictions of effective neutrino mass parameters in the 3+1 scheme are significantly different from the three neutrino paradigm.

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arXiv2024

Data driven approach to study the transition from dispersive to dissipative systems through dimensionality reduction techniques

Complexity is often exhibited in dynamical systems, where certain parameters evolve with time in a strange and chaotic nature. These systems lack predictability and are common in the physical world. Dissipative systems are one of such systems where the volume of the phase space contracts with time. On the other hand, we employ dimensionality reduction techniques to study complicated and complex data, which are tough to analyse. The Principal Component Analysis (PCA) is a dimensionality reduction technique used as a means to study complex data. Through PCA, we studied the reduced dimensional features of the numerical data generated by a nonlinear partial differential equation called the Korteweg de Vries (KdV) equation, which is a nonlinear dispersive system, where solitary waves travel along a specific direction with finite amplitude. Dissipative nature, specific to that of the Lorenz system, were observed in the dimensionally reduced data, which implies a transition from a dispersive system to a dissipative system.

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arXiv2023

Deviations from $μ$-$τ$ symmetry using $Δ$(27) group on neutrino masses and mixings

Implication of neutrino mass model based on $Δ$(27) discrete flavor symmetry, on parameters of neutrino oscillations, CP violation and effective neutrino masses is studied using type-I seesaw mechanism. The Standard Model particle content is extended by adding two additional Higgs doublets, three right-handed neutrinos and two scalar triplets under $Δ$(27) symmetry predicting diagonal charged lepton mass matrix. This can generate the desired deviation from $μ- τ$ symmetry. The resulting neutrino oscillation parameters are well agreed with the latest global fit oscillation data. The sum of the three absolute neutrino mass eigenvalues, $\sum\limits_{i}|m_{i}|$ (i=1,2,3) is found to be consistent with that of the value given by latest Planck cosmological data, $\sum\limits_{i}|m_{i}|<$0.12 eV. The model further predicts effective neutrino masses for neutrinoless double beta decay, 4.15 meV $\leq m_{ee}\leq$ 30.6 meV, tritium beta decay, 8.4 meV $\leq m_β\leq$ 30.5 meV, Jarlskog invariant, $J_{CP}=\pm 0.022$ for CP violation, baryon asymmetry $Y_{B}=1.15 \times 10^{-10}$ for normal hierarchical case; and also 49.5 meV $\leq m_{ee}\leq$ 51.7 meV, 49.5 meV $\leq m_β\leq$ 51.4 meV, $J_{CP}=\pm 0.022$, $Y_{B}=1.12\times 10^{-10}$ for inverted hierarchical case respectively.

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arXiv2023

Stability of the next-to-tribimaximal mixings under radiative corrections with the variation of SUSY breaking scale in MSSM

We analyse the radiative stability of the next-to-tribimaximal mixings ($NTBM$) with the variation of SUSY breaking scale ($m_S$) in MSSM, for both normal ordering (NO) and inverted ordering (IO) at the fixed input value of seesaw scale $M_R = 10^{15}$ GeV and two different values of $\tan β$. All the neutrino oscillation parameters receive varying radiative corrections irrespective of the $m_S$ values at the electroweak scale, which are all within $3σ$ range of the latest global fit data at low value of $\tan β$ (30). NO is found to be more stable than IO for all four different NTBM mixing patterns.

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arXiv2023

Stability of neutrino oscillation parameters at low energy scale with the variations of SUSY breaking scale under Renormalisation Group Equations

We discuss the stability of the neutrino oscillation parameters at low energy scale including self-complementarity (SC) relations among mixing angles under radiative corrections with the variation of SUSY breaking scale ($m_s$) in both normal and inverted hierarchical cases. We observe that the neutrino oscillation parameters including the SC relation maintains stability at the electroweak scale within $1σ$ range of the latest global fit data. NH case maintains more stability than IH case. All the numerical values related to the absolute neutrino masses viz., $Σ|m_i|$, $m_β$ and $m_{ ββ}$ are found to lie below the observational upper bound.

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arXiv2023

KeV dark matter in minimal extended seesaw model and its predictions in neutrinoless double beta decay and baryogenesis

We develop an $A_4 \times Z_4 \times Z_2$ symmetry extension of Standard Model under the minimal extended seesaw (MES) mechanism which successfully predicts neutrino masses and mixings patterns. This model breaks $μ-τ$ symmetry of neutrino mass matrix and explains leptonic mixing with non-zero $θ_{13}$. We study the phenomenological results of the keV-scale sterile neutrino as a dark matter candidate along with other phenomenologies such as neutrino oscillation observables, neutrinoless double beta decay, baryogenesis via leptogenesis, etc. Dirac CP-violating phase $δ_{CP}$ and two Majorana phases $α$ and $β$ are also calculated from the leptonic mixing matrix. Best-fit values of the model parameters and neutrino observables are calculated from $χ^2$ analysis. The model predicts best-fit values of neutrino mixing angles to be $\sin^2θ_{23}=0.555,\ \sin^2θ_{12}=0.301$ and $\sin^2θ_{13}=0.022$ for normal hierarchy. Significant results consistent with experimental data are also observed for effective neutrino mass $m_{ββ} \sim (0.97 - 5.02)$ meV, effective electron mass $m_β \sim (0.084-0.41)$eV and sum of active neutrino masses $\sum m_{i} < 0.12$ eV. The model does not favour Inverted hierarchy at the 3$σ$ level with the given parameter space.

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arXiv2022

Effects of variations of SUSY breaking scale on neutrino parameters at low energy scale under radiative corrections

The paper addresses the effects of the variations of the SUSY breaking scale $m_s$ in the range (2-14) TeV on the three neutrino masses and mixings, in running the renormalization group equations (RGEs) for different input values of high energy seesaw scale $M_R$, in both normal and inverted hierarchical neutrino mass models. The present investigation is a continuation of the earlier works based on the variation of $m_s$ scale. Two approaches are adopted one after another - bottom-up approach for running gauge and Yukawa couplings from low to high energy scale, followed by the top-down approach from high to low energy scale for running neutrino parameters defined at high energy scale, along with gauge and Yukawa couplings. A self-complementarity relation among three mixing angles is also employed in the analysis. Significant effect due to radiative corrections on neutrino parameters with the variation of SUSY breaking scale $m_s$, is observed.

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arXiv2022

Deviation from Tribimaximal mixing using $A_{4}$ flavour model with five extra scalars

A modified neutrino mass model with five extra scalars is constructed using $A_{4}$ discrete symmetry group. The resultant mass matrix is able to give necessary deviation from Tribimaximal mixing which reproduces the current neutrino masses and mixing data with good accuracy. The model gives testable prediction for the future measurements of the neutrinoless double-beta decay parameter $|m_{ββ}|$. The analysis is consistent with latest cosmological bound $Σm_{i}\leq$ 0.12 eV.

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arXiv2022

Deviations from Tribimaximal and Golden Ratio mixings under radiative corrections of neutrino masses and mixings

The impact of renormalization group equations(RGEs) on neutrino masses and mixings at high energy scales in Minimal Supersymmetric Standard Model(MSSM) is studied using two different mixing patterns such as Tri-Bimaximal(TBM) mixing and Golden Ratio(GR) mixing in consistent with cosmological bound of the sum of three neutrino masses, $\sum _{i}|m_{i}|$. Magnifications of neutrino masses and mixing angles at low energy scale, are obtained by giving proper input masses, and mixing angles from TBM mixing matrix and GR mixing matrix at high energy scales. High energy scales, $M_{R}$ such as $10^{13}$GeV,$10^{14}$GeV,$10^{15}$GeV are employed in the analysis. The large solar($θ_{12}$) and atmospheric($θ_{23}$) neutrino mixing angles with zero reactor angle ($θ_{13}$) from both TBM mixing matrix and GR mixing matrix at high scale, can magnify the reactor angle($θ_{13}$) at low energy scale in 3$σ$ confidence level. Both cases of normal hierarchy(NH) and inverted hierarchy(IH) are addressed here. In normal hierarchical case, it is found that $θ_{23}\simeq51.1^{\circ}$ and that in inverted hierarchical case is $θ_{23}\simeq39.1^{\circ}$ in both mixing patterns. Possibility of $θ_{23}>45^{\circ}$ or $θ_{23}<45^{\circ}$ is observed at low scale. The analysis shows the validity of the two mixing patterns at high energy scale.

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arXiv2022

Active-Sterile neutrino masses and mixings in $A_4$ minimal extended seesaw mechanism

Assuming the existence of an eV or KeV scale sterile neutrino, we develop a 3+1 neutrino mass model using $A_4\times Z_4 \times Z_2$ symmetry group. Three Higgs $H, H^{\prime}$ and $H^{\prime\prime}$ are considered to give a desired neutrino mass matrix which generates non-zero $θ_{13}$. The model can give neutrino mixing parameters that are well within the experimental 3$σ$ bounds. We also calculate the $4\times 4$ active-sterile neutrino mixing matrix, and it is found to be consistent with experimental bounds.

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arXiv2016

Generating nonzero $θ_{13}$ without breaking the $2$-$3$ symmetry of neutrino mass matrix

The prediction of vanishing reactor angle was thought to be a signature of $2$-$3$ symmetry of neutrino mass matrix. But the present study addresses certain interesting facts related with $2$-$3$ symmetry which are not addressed so far. The investigation highlights that $θ_{13}=0$, corresponds to a very special case in association with $2$-$3$ symmetry and to engender a non-zero $θ_{13}$, the breakdown of $2$-$3$ symmetry is not essential.

hep-ph↗

arXiv2016

Modulated bimaximal neutrino mixing

The present article is an endeavor to look into some fruitful frameworks based on "Bi-maximal" neutrino mixing, from a model independent stand. The possibilities involving the correction or attenuation of the original BM mixing matrix, followed by GUT-inspired charged lepton correction are invoked. The "symmetry-basis" thus constructed, accentuates some interesting facets such as: a modified QLC relation, $θ_{12}+θ_{c}\approx\fracπ{4}-θ_{13}\cos(nπ-δ_{CP})$, a possible link up between neutrino and charged lepton sectors, $θ_{13}^ν=θ_{12}^{l}\sim\mathcal{O}(θ_{C})$ or that between neutrinos and quarks, $θ_{13}^ν=θ_{C}$. The study vindicates the relevance of the Bi-maximal mixing as a first approximation.

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arXiv2016

The mixing angle as a function of neutrino mass ratio

In the quark sector, we experience a correlation between the mixing angles and the mass ratios. A partial realization of the similar tie-up in the neutrino sector helps to constrain the parametrization of masses and mixing, and hints for a predictive framework. We derive five hierarchy dependent textures of neutrino mass matrix with minimum number of parameters ($\leq\,4$), following a model-independent strategy.

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arXiv2015

Parametrization of lepton mixing matrix in terms of deviations from bi-maximal and tri-bimaximl mixing

We parametrize lepton mixing matrix, known as PMNS matrix, in terms of three parameters which account deviations of three mixing angles from their bi-maximal or tri-bimaximal values. On the basis of this parametrization we can determine corresponding charged lepton mixing matrix in terms of those three parameters which can deviate bi-maximal or tri-bimaximal mixing. We find that the charged lepton mixing matrices which can deviate bi-maximal mixing matrix and tri-bimaximal mixing matrix exhibit similar structures. Numerical analysis shows that these charged lepton mixing matrices are close to CKM matrix of quark sector.

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arXiv2015

On the ambiguities in the tri-bimaximal mixing matrix and corresponding charged lepton corrections

Two negative signs naturally appear in the $U_{μ1}$ and $U_{τ2}$ elements of the Tri-bimaximal (TBM) matrix for positive values of the mixing angles $θ_{12}$ and $θ_{23}$. Apart from this, in other TBM matrices negative signs are shifted to other elements in each case. They account for positive as well as negative values of $θ_{12}$ and $θ_{23}$. We discuss the sign ambiguity in the TBM matrix and find that the TBM matrices, in fact, can be divided into two groups under certain circumstances. Interestingly, this classification of TBM matrices is accompanied by two different $μ-τ$ symmetric mass matrices which can separately be related to the groups. To accommodate non-zero value of $θ_{13}$ and deviate $θ_{23}$ towards first octant, we then perturb the TBM mixing ansatz with the help of charged lepton correction. The diagonalizing matrices for charged lepton mass matrices also possess sign ambiguity and respect the grouping of TBM matrices. They are parametrized in terms of the Wolfenstein parameter $λ$ and satisfy unitarity condition up to second order in $λ$.

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