arXiv subjects

Kalpana Bora

Publications and source records attributed to Kalpana Bora.

At least 19 recordsLinked to original sources

arXiv2024

Sensitivity of octant of $θ_{23}$, CP violation and mass hierarchy in NO$ν$A with multinucleon and detector effects

In this work, we investigate how multinucleon enhancement and RPA (Random Phase Approximation) suppression can affect the measurement of three unknown neutrino oscillation parameters - the CP-violating phase $δ_{CP}$, the octant of the atmospheric mixing angle $θ_{23}$, and the determination of the mass hierarchy, in the appearance channel of the NO$ν$A experiment. We include the presence of the detector effect as well in the analysis, which is crucial for capturing realistic experimental scenarios. We also conducted a comparison between the nuclear model Effective Spectral Function (calculated within the RFG model) with and without Transverse Enhancement in terms of sensitivity analysis. It is found that the analysis using our comprehensive model QE(+RPA)+2p2h along with Effective Spectral Function+Transverse Enhancement exhibits significantly enhanced sensitivity compared to the pure QE interaction process, in all the cases.Also, the higher octant of $θ_{23}$, the lower half plane of $δ_{CP}$, and the normal mass hierarchy (HO-LHP-NH) exhibit improved sensitivity, enabling a more precise determination of the corresponding parameters. Furthermore, it is also noted that improving the performance of the detector also improves the results. Thus, including multinucleon effects and improving detector efficiency have the potential to enhance the capabilities of the NO$ν$A (and other long baseline) experiment in conducting precise parameter studies.

hep-ph↗

arXiv2024

Scalar Dark Matter and Stability of Higgs Vacuum within a Minimal SO(10) GUT Model

In this work, we delve to investigate a feasible range of dark matter (DM) masses within a non-supersymmetric $SO(10)$ Grand Unified Theory (GUT) scalar dark matter model, in freeze-out scenario. This model includes a singlet scalar denoted as S and an inert doublet represented by $ϕ$. Being part of SO(10), the quantum numbers of DM particles are assigned and hence we know their nature. These fields are odd under a discrete $Z_2$ matter parity $(-1)^{3(B-L)}$. The dark matter with mass 300 $\leq M_{DM} \leq$ 1000 GeV emerges as a mixture of the $Z_2$-odd scalar singlet $S$ and the neutral element of the doublet $ϕ$, both residing within a \textbf{16}-dim scalar representation of $SO(10)$. In this work we consider a real scalar \textbf{S} belonging to \textbf{16} of SO(10) as DM. We also investigate the one-loop vacuum stability through the solution of Renormalization Group Equations (RGEs) for the model's parameters. Subsequently, we scrutinize the model's predictions within the confines of contemporary theoretical and experimental restrictions. In addition to achieving vacuum stability in the SO(10) framework, the DM mass is found to lie in the previously unaddressed (theoretically) intermediate mass region of 300$\leqslant$ MDM $\leqslant$ 1000 GeV which also adheres to many current phenomenological constraints, like recent direct experimental bounds from XENON1T, indirect detection bounds from Fermi-LAT experiment, Higgs invisible decay and Electroweak Precision Test. The stability of the electroweak vacuum is seen to be present up to the Planck scale. These model predictions possess the potential for future validation through dark matter search experiments, as they are testable in future DM search experiments, along with the added feature that the model is a part of an elegant grand unified theory.

hep-ph↗

arXiv2024

Counting the uncounted : estimating the unaccounted COVID-19 infections in India

Undetected infectious populations have played a major role in the COVID-19 outbreak across the globe and estimation of this undetected class is a major concern in understanding the actual size of the COVID-19 infections. Due to the asymptomatic nature of some infections, many cases have gone undetected. Also, despite carrying COVID-19 symptoms, most of the infected population kept the infections hidden and stayed unreported, especially in a country like India. Based on these factors, we have added an undetected compartment to the already developed SEIR model [48] to estimate these uncounted infections. In this article, we have applied Physics Informed Neural Network (PINN) to estimate the undetected infectious populations in the 20 worst-affected Indian states as well as India as a whole. The analysis has been carried out for the first as well as second surge of COVID-19 infections in India. A ratio of the active undetected infectious to the active detected infectious population is calculated through the PINN analysis which gives a picture of the real size of the pandemic in India. The rate at which symptomatic infectious population goes undetected and are never reported is also estimated using the PINN method. Toward the end, an artificial neural network (ANN) based forecasting scenario of the pandemic in India is presented. The prediction is found to be reliable as the training of the neural network has been carried out using the unique features, obtained from the state-wide analysis of the newly proposed model as well as from the PINN analysis.

q-bio.PE↗

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.

hep-ph↗

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.

hep-ph↗

arXiv2023

Impact of Nuclear effects in Energy Reconstruction Methods on Sensitivity of Neutrino Oscillation Parameters at NO$ν$A experiment

Long baseline (LBL) neutrino experiments aim to measure the neutrino oscillation parameters to high precision. These experiments use nuclear targets for neutrino scattering and hence are inflicted with complexities of nuclear effects. Nuclear effects and their percolation into sensitivity measurement of neutrino oscillations parameters are not yet fully understood and therefore need to be dealt with carefully. In a recent work [1], we reported some results on this for NO$ν$A experiment using the kinematic method of neutrino energy reconstruction, where it was observed that the nuclear effects are important in sensitivity analysis, and inclusion of realistic detector setup specifications increases uncertainty in this analysis as compared to ideal detector case. With this motivation, in this work, we use two methods of neutrino energy reconstruction - kinematic and calorimetric, including the nuclear effects, and study their impact on sensitivity analysis. We consider nuclear interactions such as RPA and 2p2h and compare two energy reconstruction methods with reference to events generation, measurement of neutrino oscillation parameters $Δm_{32}^2$ and $θ_{23}$ for disappearance channel, mass hierarchy sensitivity, and CP-violation sensitivity for appearance channel of the NO$ν$A experiment. It is observed that with an ideal detector setup, the kinematic method shows significant dependence on nuclear effects compared to the calorimetric method. We also investigate the impact of realistic detector setup for NO$ν$A in these two methods (with nuclear effects) and find that the calorimetric method shows more bias (uncertainty increases) in sensitivity contours, as compared to the kinematic method. This is found to be true for both the mass hierarchies and for both neutrino and antineutrino incoming beams.

hep-ph↗

arXiv2023

Uncertainties in neutrino oscillation parameter sensitivity due to resonance processes at NO$ν$A

The long baseline (LBL) neutrino experiments use heavy nuclear targets for neutrino scattering in which nuclear effects give rise to complications in measuring the neutrino oscillation parameters up to high precision. These nuclear effects are not yet fully understood and therefore need to be quantified as they contribute to the systematic uncertainties. Precision reconstruction of neutrino energy is one of the main components in measuring the oscillation parameters, and it is required that the neutrino energy is reconstructed with very high precision. In this work, we investigate the effects of the resonance (RES) interaction process using two models for carbon target for $ν_μ\rightarrowν_μ$ disappearance channel of the NO$ν$A experiment, on neutrino-nucleus scattering cross section, events, and neutrino oscillation parameter sensitivity. We also incorporate the realistic detector specifications of NO$ν$A. To quantify the systematic uncertainties due to RES interactions, we compare the cross-sections, events, and sensitivity analysis for two models of RES processes - Rein-Sehgal and Berger-Sehgal, and comment on which model produces more precision. We observe that RES processes contribute significantly, and should be included carefully in models while extracting neutrino oscillation parameters.

hep-ph↗

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.

hep-ph↗

arXiv2022

A new viable mass region of Dark matter and Dirac neutrino mass generation in a scotogenic extension of SM

We propose a scotogenic extension of the Standard Model which can provide a scalar Dark Matter candidate in the new, theoretically previously unaddressed, intermediate region ($200\leq M_{DM}\leq 550$ GeV) and also generate light Dirac neutrino masses. In this framework, the standard model is extended by three gauge singlet fermions, two singlet scalar fields, and one additional scalar doublet, all of which are odd under $Z_{2} \times Z_{4}$ discrete symmetry. These additional symmetries prevent the singlet fermions from obtaining Majorana mass terms along with providing the stability to the dark matter candidate. It is known that in the case of the scalar singlet DM model, the only region which is not yet excluded is a narrow region close to the Higgs resonance $m_{S} \simeq\frac{m_{h}}{2}$ - others ruled out from different experimental and theoretical bounds. In the case of the Inert doublet model, the mass region ($\sim 60$-$80$ GeV) and the high mass region (heavier than $ 550 $ GeV) are allowed. This motivates us to explore a parameter range in the intermediate-mass region $M_{W}\leq M_{DM}\leq 550 $ GeV, which we do in a scotogenic extension of SM with a scalar doublet and scalar singlets. The dark matter in our model is a mixture of singlet and doublet scalars. We constrain the allowed parameter space of the model using Planck bound on present dark matter relic abundance, neutrino mass, and the latest bound on spin-independent DM-nucleon scattering cross-section from XENON1T experiment. Our model may provide a viable DM candidate in the new, previously unexplored mass range ($200\leq M_{DM}\leq 550$ GeV), if this new window for the DM candidate mass is detected in future experiments, along with explanation of Dirac mass of neutrinos, since so far there is no strong evidence in support of Majorana nature of neutrino mass.

hep-ph↗

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.

hep-ph↗

arXiv2022

Uncertainties in the oscillation parameters measurement due to multi-nucleon effects at NO$ν$A Experiment

In this work, we investigate the role of multi-nucleon (MN) effects (mainly 2p-2h and RPA) on the sensitivity measurement of various neutrino oscillation parameters, in the disappearance channel of NO$ν$A (USA) experiment. Short-range correlations and detector effects have also been included in the analysis. We use the kinematical method of reconstruction of the incoming neutrino energy, both at the near and far detectors. The extrapolation technique has been used to estimate oscillated events at the far detector. The latest global best fit values of various light neutrino oscillation parameters have been used in the analysis. We find that MN effects increase uncertainty in the measurement of neutrino oscillation parameters, while lower detector efficiency is reflected in more uncertainty. This study can give useful insight into precision studies at long-baseline neutrino experiments in future measurements.

hep-ph↗

arXiv2022

A new experiment to detect dark matter in sub-MeV range using semiconductor superlattice superstructures (SSS)

About $26\%$ of the matter in our Universe is made up of Dark Matter (DM), which interacts with Standard Model (SM) matter only through gravitational or weak interactions. Many proposals have been made by scientists about the possible candidates of DM - WIMPs, axions, ALPs, black holes etc. And range of its mass could be extremely broad - from Planck scale to as light as $10^{-22}$ eV. Experiments to detect DM are extremely challenging, as DM does not exhibit appreciable interactions with ordinary matter. May be due to such elusive nature, so far it has not been possible to detect DM, though many experiments are going on worldwide to do so. With about 40 orders of magnitude variation in their mass, it is possible that their gravitational interaction too is very weak, and many creative proposals have been made to detect possible DM candidates, with vast variation of techniques and target materials. In this work, we propose a new experiment to detect sub-MeV range DM particles, using the semiconductor superlattice superstructure (SSS) as the target material. Such materials have band gap of the order of few hundreds of milli eV, and are suitable for detecting sub-MeV range particles scattering off electrons. The photons emitted as a result of excitation of SSS lie in the micrometer range and may be detected via quantum cascade lasers (QCL).

hep-ex↗

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 $<10^{-5}$.

hep-ph↗

arXiv2018

Compatibility of $A_{4}$ Flavour Symmetric Minimal Extended Seesaw with $(3+1)$ Neutrino Data

Motivated by the recent resurrection of the evidence for an eV scale sterile neutrino from the MiniBooNE experiment, we revisit one of the most minimal seesaw model known as the minimal extended seesaw that gives rise to a $3+1$ light neutrino mass matrix. We consider the presence of $A_4$ flavour symmetry which plays a non-trivial role in generating the structure of the neutrino mass matrix. Considering a diagonal charged lepton mass matrix and generic vacuum alignments of $A_4$ triplet flavons, we classify the resulting mass matrices based on their textures. Keeping aside the disallowed texture zeros based on earlier studies of $3+1$ neutrino textures, we categorise the remaining ones based on texture zeros, $μ-τ$ symmetry in the $3\times3$ block and hybrid textures. After pointing out the origin of such $3+1$ neutrino textures to $A_4$ vacuum alignments, we use the latest $3+1$ neutrino oscillation data and numerically analyse the texture zeros and $μ-τ$ symmetric cases. We find that a few of them are allowed from each category predicting interesting correlations between neutrino parameters. We also find that all of these allowed cases prefer normal hierarchical pattern of light neutrino masses over inverted hierarchy.

hep-ph↗

arXiv2017

Probing Majorana Neutrino Textures at DUNE

We study the possibility of probing different texture zero neutrino mass matrices at long baseline neutrino experiment DUNE. Assuming a diagonal charged lepton basis and Majorana nature of light neutrinos, we first classify the possible light neutrino mass matrices with one and two texture zeros and then numerically evaluate the parameter space in terms of atmospheric mixing angle $θ_{23}$ and Dirac CP phase $δ_{\text{CP}}$ which satisfies the texture zero conditions. We then feed these parameter values into the numerical analysis in order to study the sensitivity of DUNE experiment to them. We find that the DUNE will be able to exclude some of these texture zero mass matrices which restrict the $(θ_{23}-δ_{\text{CP}})$ to a very specific range of values.

hep-ph↗

arXiv2017

Effects Of leptonic non-unitarity on lepton flavor violation, neutrino oscillation, leptogenesis and lightest neutrino mass

Neutrino Physics is a mature branch of science with all the three neutrino mixing angles and two mass squared differences determined with high precision. Inspite of several experimental verifications of neutrino oscillations and precise measurements of two mass squared differences and the three mixing angles, the unitarity of the leptonic mixing matrix is not yet established, leaving room for the presence of small non-unitarity effects. Deriving the bounds on these non-unitarity parameters from existing experimental constraints, on cLFV decays such as, $ μ\rightarrow eγ$, $ μ\rightarrow τγ$, $ τ\rightarrow eγ$, we study their effects on the generation of baryon asymmetry through leptogenesis and neutrino oscillation probabilities. We consider a model where see-saw is extended by an additional singlet $ S $ which is very light, but can give rise to non-unitarity effects without affecting the form on see-saw formula. We do a parameter scan of a minimal see-saw model in a type I see-saw framework satisfying the Planck data on baryon to photon ratio of the Universe, which lies in the interval, $5.8\times 10^ {-10} < Y _{B} < 6.6 \times 10^ {-10} (BBN)$. We predict values of lightest neutrino mass, and Dirac and Majorana CP-violating phase $ δ_{CP} $, $ α$ and $ β$, for normal hierarchy and inverted hierarchy for one flavor leptogenesis. It is worth mentioning that all these four quantities are unknown yet, and future experiments will be measuring them.

hep-ph↗

arXiv2016

Pomeron inspired Neutrino-nucleon Cross Section in Ultra High Energy

Studies on neutrino-nucleon ($νN$) cross sections at different energy scales have regained interest due to increasing importance of precision measurements, as they are needed as an ingredient in all neutrino experiments. In this paper we have calculated both charged current (CC) and neutral current (NC) $ν$N scattering cross sections at Ultra High Energy (UHE) regime in the neutrino energy ($E_ν$) region i.e. $10^{9} GeV \le E_ν \le 10^{12}$ GeV using QCD inspired double asymptotic limit fit of electron-proton structure function $F_{2}^{ep}$ to low $\mathit{x}$ HERA data. The form $F_{2}^{ep} \sim x^{-λ(Q^{2})}$ used in our analysis, can be conjectured like a dynamic pomeron (DP)-type behaviour. We also find an analytic form of the total cross sections, $σ_{CC}^{νN}$ and $σ_{NC}^{νN}$ which appear to be of hard-pomeron exchange types. A comparative analysis of our results with those available in literature is also done. An improved understanding of $νN$ interactions at UHE are essentially important for future oscillation experiments. Future measurements will support/confront our predictions. \textbf{Keywords}: Neutrino cross section, Ultra High Energy, QCD, Double Asymptotic limit, dynamic pomeron, hard-pomeron.

hep-ph↗

arXiv2016

Octant Degeneracy, Quadrant of leptonic CPV phase at Long Baseline Neutrino Experiments and Baryogenesis

In a recent work by us, we have studied, how CP violation discovery potential can be improved at long baseline neutrino experiments (LBNE/DUNE), by combining with its ND (near detector) and reactor experiments. In this work, we discuss how this study can be further analysed to resolve entanglement of the quadrant of leptonic CPV phase and Octant of atmospheric mixing angle $ θ_{23} $, at LBNEs. The study is done for both NH (Normal hierarchy) and IH (Inverted hierarchy), HO (Higher Octant) and LO (Lower Octant). We show how baryogenesis can enhance the effect of resolving this entanglement, and how possible values of the leptonic CP-violating phase $ δ_{CP} $ can be predicted in this context. With respect to the latest global fit data of neutrino mixing angles, we predict the values of $ δ_{CP} $ for different cases. In this context we present favoured values of $ δ_{CP} $ ($ δ_{CP} $ range at $ \geq $ 2$ σ$ ) constrained by the latest updated BAU range and also confront our predictions of $ δ_{CP} $ with an up-to-date global analysis of neutrino oscillation data. We find that some region of the favoured $ δ_{CP} $ parameter space lies within the best fit values around $ δ_{CP} \simeq 1.3π-1.4 π$. A detailed analytic and numerical study of baryogenesis through leptogenesis is performed in this framework in a model independent way.

hep-ph↗