arXiv subjects

Chandan Duarah

Publications and source records attributed to Chandan Duarah.

11 recordsLinked to original sources

arXiv2026

Deviation from $μ-τ$ reflection symmetry under radiative corrections in the minimal seesaw framework

The $μ$-$τ$ reflection symmetry predicts a maximal atmospheric mixing angle, $θ_{23}=π/4$, and Dirac CP phase, $δ=π/2$ or $3π/2$. Recent global analyses indicate small but significant deviations from these predictions, suggesting that the symmetry is approximate and requires breaking. Motivated by this, we study the breaking of $μ$-$τ$ reflection symmetry induced by radiative corrections in the minimal seesaw framework, assuming the symmetry to be exact at the high-energy seesaw scale $Λ_{μτ}=10^{14}~\mathrm{GeV}$. A distinctive feature of the minimal seesaw is that one light neutrino remains massless, leaving only one physical Majorana CP phase. Starting from the integral solution of the one-loop RGE for the effective Majorana neutrino mass matrix, we derive analytical expressions for the low-energy neutrino parameters at $Λ_{\mathrm{EW}}=172.76~\mathrm{GeV}$ in terms of their high-energy counterparts. We then numerically estimate the low-energy parameters within the MSSM, taking $Λ_s=1~\mathrm{TeV}$ and $\tanβ=10$, $30$ and $50$. The analysis is performed separately for Normal Order (NO) and Inverted Order (IO). We find that the predicted neutrino masses and mixing parameters are consistent with current experimental data in both scenarios. The sum of neutrino masses, Jarlskog invariant $J$, and effective Majorana mass $|\langle m\rangle_{ee}|$ also satisfy current experimental constraints. Finally, we estimate the amount of deviations of the low-energy neutrino parameters from their high-energy values and investigate their dependence on $\tanβ$. We find that the magnitude of these deviations increases with increasing $\tanβ$ for both NO and IO.

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arXiv2026

Effects of RG running in breaking $μ-τ$ reflection symmetry, conventional versus minimal seesaw

The $μ$--$τ$ reflection symmetry has attracted considerable attention owing to its prediction of a maximal atmospheric mixing angle and a Dirac CP-violating phase $δ=3π/2$, consistent with indications from the T2K and NO$ν$A experiments. Since current neutrino oscillation data exhibit small but significant deviations from the exact symmetry predictions, understanding the origin of its breaking has become an important problem. In this work, we investigate the radiative breaking of $μ$--$τ$ reflection symmetry within the framework of the minimal seesaw model through the renormalization group (RG) evolution of neutrino parameters. Assuming the symmetry to be exact at the flavor symmetry (seesaw) scale, we examine whether the observed low-energy neutrino oscillation data can be reproduced after RG evolution. Owing to the rank-two structure of the minimal seesaw model, one light neutrino mass eigenvalue vanishes, reducing the number of independent high-energy neutrino parameters from five to four. We perform a systematic numerical analysis to determine the allowed high-energy parameter space capable of reproducing the current experimental constraints at low energies. Furthermore, a comparative study between the conventional Type-I seesaw and the minimal seesaw frameworks is carried out by analyzing the RG evolution of the solar and atmospheric mass-squared differences.

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arXiv2026

An A4 model to accommodate maximal theta23 and maximal delta consistent with mu-tau reflection symmetry

In this work, we construct an A4-based flavor symmetry model within the framework of the type-I seesaw mechanism to realize a light neutrino mass matrix consistent with mu-tau reflection symmetry. The entire framework is based on the Standard Model gauge symmetry extended by the discrete group A4 x Z2 x Z4. In general, the elements of the light Majorana neutrino mass matrix are complex. The mu-tau reflection symmetric texture of the mass matrix can be realized in a generalized CP symmetry limit. In this symmetry limit, the model predicts a maximal atmospheric mixing angle theta23 = pi/4 and a maximal Dirac CP phase delta = pi/2 or 3pi/2. These features are consistent with current experimental observations, including a near-maximal value of theta23, a non-zero reactor angle, and a preference for delta close to 270 degrees, as indicated by the T2K and NOvA experiments. Non-maximal values of theta23 and delta can be accommodated when one does not restrict to the CP symmetry limit. The model predictions for the mixing angles and the Dirac CP phase delta are then controlled by two parameters. We perform a numerical analysis to identify the allowed values of the model parameters consistent with current global three-neutrino oscillation data. The model successfully reproduces the desired deviations of theta23 and delta from their maximal values, consistent with global fit data, while simultaneously accommodating the observed values of theta12 and theta13.

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arXiv2026

Predictions of effective Majorana neutrino mass under radiative corrections to $μ-τ$ reflection symmetry

The search for neutrinoless double beta decay ($0νββ$) is currently one of the key objectives in neutrino physics research. The decay rate of $0νββ$ decay depends on the effective Majorana neutrino mass $|\langle m \rangle_{ee}|$. In this work we study the numerical prediction of $|\langle m \rangle_{ee}|$ in the scenario of deviation from the $μ$-$τ$ reflection symmetry due to radiative corrections, as an extension of our earlier work \cite{pegu}. In \cite{pegu}, we consider an exact $μ$-$τ$ reflection symmetry in the light effective Majorana neutrino mass matrix and in the corresponding lepton mixing matrix as well at the seesaw scale. We choose numerical values of all the mixing parameters and neutrino mass eigenvalues at the seesaw scale as inputs and estimate the values of mass eigenvalues and mixing parameters at the electroweak scale due to radiative corrections. We find these low energy predictions consistent with global $3σ$ oscillation data. In the present work, we compute the effective Majorana neutrino mass $|\langle m \rangle_{ee}|$ using these low energy values at the electroweak scale. We find that the low energy predictions of $|\langle m \rangle_{ee}|$ are consistent with the latest upper bound $|\langle m \rangle_{ee}|<(0.028-0.122)\ eV$ provided by KamLAND-Zen Collaboration.

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arXiv2025

Renormalization group evolution induced breaking of $μ-τ$ reflection symmetry in MSSM with effects of variation of $tanβ$

We study the renormalization group (RG) evolution induced breaking of $μ$--$τ$ reflection symmetry in the Minimal Supersymmetric Standard Model (MSSM), with a special focus on the effects of varying $\tanβ\equiv v_u/v_d$, the ratio of MSSM Higgs vacuum expectation values. Starting from an exact $μ$--$τ$ reflection symmetry imposed at a high flavor symmetry scale $Λ_{\text{FS}}$, we run the complete set of coupled RGEs for neutrino masses, mixing angles, and CP-violating phases down to the electroweak scale, imparting perturbation to the symmetry. We consider a specific value of the SUSY breaking scale, $Λ_s=7\ TeV$ during the run. By choosing suitable free parameters at the high-energy scale, we reproduce the low-energy experimental constraints on neutrino observables consistent with $3ν$ global analysis data. We then examine how the breaking of $μ$--$τ$ reflection symmetry is influenced by different values of $\tanβ$, considering three benchmark choices. In addition, the analysis is performed for both normal ordering (NO) and inverted ordering (IO) of neutrino masses to highlight potential differences in their RG running behavior.

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arXiv2025

Perturbations to $μ-τ$ reflection symmetry due to renormalization group running effects

$μ-τ$ reflection symmetry is an attractive flavour symmetry in lepton mixing, which accommodates maximal values of atmospheric mixing angle ($θ_{23}=π/4$) and Dirac CP phase ($δ=π/2/3π/2$). Another significance of this symmetry is that it does not constrain $θ_{13}$ to be zero. As the recent results from $T2K$ and $NOνA$ experiments indicate a near-maximal value of the Dirac CP phase, the role of $μ-τ$ reflection symmetry becomes more prominent. In this work, we study RG running effects as a perturbation to the $μ-τ$ reflection symmetry. Assuming the symmetry to be preserved at the seesaw scale, we study the deviations of mass eigenvalues and lepton mixing parameters at the electroweak scale due to RG running. We derive the one-loop RGEs of the mass eigenvalues and mixing parameters and solve them numerically. Numerical analysis shows that the deviations from $μ-τ$ reflection symmetry are consistent with $3σ$ range of global oscillation data.

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arXiv2021

Mu-Tau Reflection Symmetry in the Standard Parametrization and Contributions from Charged Lepton Sector

The $μ-τ$ reflection symmetry of the lepton mixing matrix accommodates maximal atmospheric mixing ($θ_{23}=π/4$) as well as maximal Dirac CP phase ($δ=\pm π/2$) for the Dirac case. In the standard parametrization of the PMNS matrix the reflection symmetric nature is not directly visible while substituting the maximal values of the mixing parameters. This issue has been addressed in this paper. It is found that the reflection symmetry in the 'standard' PMNS matrix can be restored by allowing maximal values of the Majorana CP phases ($α$, $β$) as well, along with maximal $δ$. To accommodate non-maximal values of $θ_{23}$ and $δ$ we consider charged lepton contributions to the neutrino mixing and implement the proposed scheme of reflection symmetry in the neutrino mixing matrix. The charged lepton correction scheme succeeds in the prediction of lepton mixing parameters consistent with the global $3ν$ oscillation data.

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arXiv2019

An Algebraic Analysis of Neutrino Masses and Mixings and its Implications on $μ$-$τ$ Symmetric Mass Matrix

We diagonalize Majorana neutrino mass matrix with the help of PMNS matrix and obtain analytical relations between the mass matrix elements and mixing parameters, viz., three mixing angles- $θ_{12}, θ_{23}, θ_{13}$ and Dirac CP phase δ. We analyse our results in a special $μ$-$τ$ symmetric mass matrix which corresponds to maximal atmospheric mixing ($θ_{23}=π/4$) and maximal CP violation ($δ=-π/2$). The analysis shows that a deviation of $θ_{23}$ from its maximal value can be correlated with the prediction of other two mixing angles.

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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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arXiv2012

Dependence of $\tan^2 θ_{12}$ on Dirac CP phase $δ$ in tri-bimaximal neutrino mixing under charged lepton correction

We consider charged lepton correction to Tri-bimaximal(TBM) neutrino mixing, defined by the relation $U_{PMNS}=U^{\dagger}_l U_{TB}$ and find possible form of $U_l$ which can impart non-zero value of $\sin θ_{13}$ as well as $\tan^2 θ_{23}<1$, consistent with latest global analysis data. We adopt a new parametrization, other than the standard PDG parametrization, to introduce Dirac CP violating phase $δ$ in the PMNS matrix which is discussed by Fritzsch. Under such charged lepton correction pattern we note that $\tan^2 θ_{12}$ becomes dependent on the CP phase $δ$ from where constraints on $δ$ phase can be obtained after employing experimental range of mixing angles. To compute the values of mixing angles we assume the charged lepton correction to be of Cabibbo-Kobayashi-Maskawa(CKM) like. Since all the mixing matrices involved in the calculation, are derived from three dimensional rotation matrices they satisfy unitarity condition.

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