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N. Nimai Singh

Publications and source records attributed to N. Nimai Singh.

49 records · Page 3Linked to original sources
arXiv2004

Discriminating neutrino mass models using Type II seesaw formula

In this paper we propose a kind of natural selection which can discriminate the three possible neutrino mass models, namely the degenerate, inverted hierarchical and normal hierarchical models, using the framework of Type II seesaw formula. We arrive at a conclusion that the inverted hierarchical model appears to be most favourable whereas the normal hierarchical model follows next to it. The degenerate model is found to be most unfavourable. We use the hypothesis that those neutrino mass models in which Type I seesaw term dominates over the Type II left-handed Higgs triplet term are favoured to survive in nature.

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arXiv2004

New Uncertainties in QCD-QED Rescaling Factors using Quadrature Method

In this paper we briefly outline the quadrature method for estimating uncertainties in a function of several variables and apply it to estimate the numerical uncertainties in QCD-QED rescaling factors. We employ here the one-loop order in QED and three-loop order in QCD evolution equations of fermion mass renormalization. Our present calculations are found to be new and also reliable compared to the earlier values employed by various authors.

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arXiv2003

Inverted Hierarchical Model of Neutrino Masses Revisited

In this letter we highlight the inherent problems associted with the inverted hierarchical model of neutrinos with only three generations and suggest possible solutions within the MSSM. we discuss the new parametrisation of the solar mixing angle which can identify the light side and dark side of the data. We then argue whether the inverted hierarchical neutrino mass matrix can explain the large mixing angle(LMA) MSW solution of the solar neutrino anomaly in the presence of an appropriate texture of charged lepton mass matrix. In model independent way we explore such specific form of the charged lepton mass matrix having special structure in 1-2 block. The contribution to the solar mass splitting arising out of radiative corrections in MSSM, is calculated, thus making the model stable under radiative corrections.

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arXiv2003

Right-handed Majorana Neutrino Mass Matrices for Generating Bimaximal Mixings in Degenerate and Inverted Models of Neutrinos

An attempt is made to generate the bimaximal mixings of the three species of neutrinos from the textures of the right-handed Majorana neutrino mass matrices. We extend our earlier work in this paper for the generation of the nearly degenerate as well as the inverted hierarchical models of the left-handed Majorana neutrino mass matrices using the non-diagonal textures of the right-handed Majorana neutrino mass matrices and the diagonal form of the Dirac neutrino mass matrices, within the frame work of the seesaw mechanism in a model independent way. Such Majorana neutrino mass models are important to explain the recently reported result on the neutrinoless double beat decay (0/nu/beta/beta) experiment,together with the earlier established data on LMA MSW solar and atmospheric neutrino oscillations.

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arXiv2002

Predictive Framework with a Pair of Degenerate Neutrinos at a high scale

Radiative generation of the solar scale $Δ_{\odot}$ is discussed in the presence of leptonic CP violation. We assume that both the solar scale and $U_{e3}$ are zero at a high scale and the weak radiative corrections generate them. It is shown that all leptonic mass matrices satisfying these requirements lead to a unique prediction $Δ_{\odot} \cos 2θ_{\odot}\approx 4 δ_τ\sin^2 θ_A |m_{ee}|^2$ for the solar scale in terms of the radiative correction parameter $δ_τ$, the physical solar (atmospheric) mixing angles $θ_{odot} (θ_A)$ and the Majorana neutrino mass $m_{ee}$ probed in neutrinoless double beta decay. This relation is independent of the mixing matrix and CP-violating phases at the high scale. The presence of CP-violating phases leads to dilution in the solar mixing angle defined at the high scale. Because of this, bi-maximal mixing pattern at the high energy leads to large but non-maximal solar mixing in the low-energy theory. An illustrative model with this feature is discussed.

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arXiv2002

Degenerate and Inverted Hierarchical Models of Majorana Neutrinos from See-saw Mechanism

In order to explain the recently reported result on the double beta decay $(0νββ)$ experiment, together with the earlier established data on LMA MSW solar and atmospheric neutrino oscillations, we generate the textures of the nearly degenerate as well as the inverted hierarchical models of the left-handed Majorana neutrino mass matrices within the framework of the see-saw mechanism in a model independent way. The leptonic mixings are generated from the texture of the right- handed Majorana mass matrices while keeping the Dirac neutrino mass matrices in diagonal forms.

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arXiv2001

LMA MSW Solution from the Inverted Hierarchical Model of Neutrinos

We examine whether the inverted hierarchical model of neutrinos is compatible with the explanation of the large mixing angles (LMA)MSW solution of the solar neutrino problem. The left-handed Majorana neutrino mass matrix for the inverted hierarchical model, is generated through the seesaw mechanism using the diagonal form of the Dirac neutrino mass matrix and the non-diagonal texture of the right-handed Majorana mass matrix. In a model independent way, we construct a specific form of the charged lepton mass matrix having a special structure in 1-2 block, which contribution to the leptonic mixing (MNS) matrix leads to the predictions $\sin^{2}2θ_{12}=0.8517$, $\sin^{2}2θ_{23}=0.9494$, and $|V_{e3}|=0.159$ at the unification scale. These predictions are found to be consistent with the LMA MSW solution of the solar neutrino problem. The inverted hierarchical model is also found to be stable against the quantum radiative corrections in the MSSM. A numerical analysis of the renormalisation group equations (RGEs) in the MSSM shows a mild decrease of the mixing angles with the decrease of energy scale and the corresponding values of the neutrino mixings at the top-quark mass scale are found as $\sin^{2}2θ_{12}=0.8472$, $\sin^{2}2θ_{23}=0.9399$, $|V_{e3}|=0.1509$ respectively.

hep-ph↗
arXiv2001

Bimaximal Mixings from the Texture of the Right-handed Majorana Neutrino Mass Matrix

We study the origin of neutrino masses and mixing angles which can accomodate the LMA MSW solutions of the solar neutrino anomaly as well as the solution of the atmospheric neutrino problem, within the framework of the see-saw mechanism. We employ the diagonal form of the Dirac neutrino mass matrices with the physical masses as diagonal elements in the hierarchical order. Such choice has been motivated from the fact that the known CKM angles for the quark sector, are relatively small. We consider both possibilities where the Dirac neutrino mass matrix is either the charged lepton or the up-quark mass matrix within the framework of SO(10) GUT with or without supersymmetry. The non-zero texture of the right-handed Majorana neutrino mass matrix $M_{R}$ is used for the generation of the desired bimaximal mixings in a model independent way. Both hierarchical and inverted hierarchical models of the left-handed Majorana neutrino mass matrices are generated and then discussed with examples.

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arXiv2000

Effects of the Scale-dependent Vacuum Expectation Values in the Renormalization Group Analysis of Neutrino Masses

The contribution of scale-dependent vacuum expectation values (VEVs) of Higgs scalars, which gives significant effects in the evolution of fundamental fermion masses in the Minimal Supersymmetric Standard Model (MSSM), is now considered in the derivation of the one-loop analytic expression for the evolution of the left-handed Majorana neutrino masses with energies. The inclusion of such effect of the running VEV increases the stability of the neutrino masses under quantum corrections and leads to a mild decrease of neutrino masses with higher energies.

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arXiv2000

Renormalisation Group Analysis of Single Right-handed Neutrino Dominance

We perform a renormalisation group (RG) analysis of neutrino masses and mixing angles in the see-saw mechanism in the minimal supersymmetric standard model with three right-handed neutrinos, including the effects of the heavy neutrino thresholds. We focus on the case that one of the right-handed neutrinos provides the dominant contribution to the 23 block of the light Majorana matrix, causing its determinant to approximately vanish and giving an automatic neutrino mass hierarchy, so called single right-handed neutrino dominance which may arise from a U(1) family symmetry. In these models radiative corrections can increase atomospheric and solar neutrino mixing by up to about 10% and 5%, respectively, and may help to achieve bi-maximal mixing. Significantly we find that the radiative corrections over the heavy neutrino threshold region are at least as important as those usually considered from the lightest right-handed neutrino down to low energies.

hep-ph↗
arXiv2000

Understanding the linear see-saw neutrino mass relations and large mixing angle MSW solution

We study the effective ways for generating the linear see-saw neutrino mass relations and large neutrino mixing angles in two classes of grand unified SO(10) models where the texture of Dirac neutrino mass matrix is related to either the charged lepton mass matrix (case A) or the up-quark mass matrix (case B). We also briefly analyse their stability criteria and they are found to be stable under under radiative corrections at low energies.

hep-ph↗
arXiv2000

Inverted Hierarchy Models of Neutrino Masses

We study models of neutrino masses which naturally give rise to an inverted mass hierarchy and bi-maximal mixing. The models are based on the see-saw mechanism with three right-handed neutrinos, which generates a single mass term of the form $ν_e(ν_μ+ν_τ)$ corresponding to two degenerate neutrinos $ν_e$ and $ν_μ+ν_τ$, and one massless neutrino $ν_μ-ν_τ$. Atmospheric neutrino oscillations are accounted for if the degenerate mass term is about $5\times 10^{-2}$ eV. Solar neutrino oscillations of the Large Mixing Angle MSW type arise when small perturbations are included leading to a mass splitting between the degenerate pair of about $(1.7-2.0)\times 10^{-4}$ eV for the successful cases. We study the conditions that such models must satisfy in the framework of a U(1) family symmetry broken by vector singlets, and catalogue the simplest examples. We then perform a renormalisation group analysis of the neutrino masses and mixing angles, assuming the supersymmetric standard model, and find modest radiative corrections of a few per cent, showing that the model is stable. At low energies we find $\sin^22θ_{23}\approx 0.93-0.96$ and $\sin^22θ_{12}\approx 0.9-1.0$.

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