arXiv subjects

Debajyoti Dutta

Publications and source records attributed to Debajyoti Dutta.

31 records · Page 2Linked to original sources

arXiv2018

Invisible neutrino decay in the light of NOvA and T2K data

We probe for evidence of invisible neutrino decay in the latest NOvA and T2K data. It is seen that both NOvA and T2K data sets are better fitted when one allows for invisible neutrino decay. We consider a scenario where only the third neutrino mass eigenstate $ν_3$ is unstable and decays into invisible components. The best-fit value for the $ν_3$ lifetime is obtained as $τ_{3}/m_{3} = 3.16\times 10^{-12}$ s/eV from the analysis of the NOvA neutrino data and $τ_{3}/m_{3} = 1.0\times 10^{-11}$ s/eV from the analysis of the T2K neutrino and anti-neutrino data. The combined analysis of NOvA and T2K gives $τ_{3}/m_{3} = 5.01\times 10^{-12}$ s/eV as the best-fit lifetime. However, the statistical significance for this preference is weak with the no-decay hypothesis still allowed at close to 1.5$σ$ C.L. from the combined data sets, while the two experiment individually are consistent with no-decay even at the 1$σ$ C.L. At 3$σ$ C.L., the NOvA and T2K data give a lower limit on the neutrino lifetime of $τ_{3}/m_{3}$ is $τ_{3}/m_{3} \geq 7.22 \times 10^{-13}$ s/eV and $τ_{3}/m_{3} \geq 1.41 \times 10^{-12}$ s/eV, respectively, while NOvA and T2K combined constrain $τ_{3}/m_{3} \geq 1.50 \times 10^{-12}$ s/eV. We also show that in presence of decay the best-fit value in the $\sin^{2}θ_{23}$ vs $Δm^{2}_{32}$ plane changes significantly and the allowed regions increase significantly towards higher $\sin^{2}θ_{23}$.

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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.

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arXiv2017

Imprints of a light Sterile Neutrino at DUNE, T2HK and T2HKK

We evaluate the impact of sterile neutrino oscillations in the so-called 3+1 scenario on the proposed long baseline experiment in USA and Japan. There are two proposals for the Japan experiment which are called T2HK and T2HKK. We show the impact of sterile neutrino oscillation parameters on the expected sensitivity of T2HK and T2HKK to mass hierarchy, CP violation and octant of $θ_{23}$ and compare it against that expected in the case of standard oscillations. We add the expected ten years data from DUNE and present the combined expected sensitivity of T2HKK+DUNE to the oscillation parameters. We do a full marginalisation over the relevant parameter space and show the effect of the magnitude of the true sterile mixing angles on the physics reach of these experiments. We show that if one assumes that the source of CP violation is the standard CP phase alone in the test case, then it appears that the expected CP violation sensitivity decreases due to sterile neutrinos. However, if we give up this assumption, then the CP sensitivity could go in either direction. The impact on expected octant of $θ_{23}$ and mass hierarchy sensitivity is shown to depend on the magnitude of the sterile mixing angles in a nontrivial way.

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arXiv2017

Effect of Non Unitarity on Neutrino Mass Hierarchy determination at DUNE, NO$ν$A and T2K

The neutrino mass ordering is one of the principal unknowns in the neutrino sector. Long baseline neutrino experiments have the potential of resolving this issue as they are sensitive to large matter effects. The superbeam experiment DUNE is one of the most promising candidates to study the neutrino mass hierarchy, along with NO$ν$A and T2K. But in the presence of non unitarity of the leptonic mixing matrix, the capability of such experiments to discriminate between the two hierarchies gets suppressed. The mass hierarchy sensitivity of DUNE decreases in the presence of new physics. In this paper we analyze the origin and extent of this loss of sensitivity at the level of oscillation probabilities, events, mass hierarchy sensitivity and the discovery reach of DUNE, NO$ν$A and T2K.

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arXiv2017

Octant of $θ_{23}$ at long baseline neutrino experiments in the light of Non Unitary Leptonic mixing

The octant of the atmospheric mixing angle $θ_{23}$ is still undetermined by neutrino oscillation experiments. Long-baseline experiments like NO$ν$A, T2K and DUNE offer good prospects for determining the octant of $θ_{23}$. However, their capability to do so may be compromised by the possible presence of non-unitarity in the leptonic mixing matrix. In this paper, we study in detail the octant degeneracy with and without non-unitarity at the level of oscillation probabilities and events for these experiments. We also analyze their octant sensitivity and discovery reach and show that they are hampered in the presence of non-unitarity.

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arXiv2016

Capabilities of long-baseline experiments in the presence of a sterile neutrino

Assuming that there is a sterile neutrino, we ask what then is the ability of long-baseline experiments to i) establish that neutrino oscillation violates CP, ii) determine the three-neutrino mass ordering, and iii) determine which CP-violating phase or phases are the cause of any CP violation that may be observed. We find that the ability to establish CP violation and to determine the mass ordering could be very substantial. However, the effects of the sterile neutrino could be quite large, and it might prove very difficult to determine which phase is responsible for an observed CP violation. We explain why a sterile neutrino changes the long-baseline sensitivities to CP violation and to the mass ordering in the ways that it does. We note that long-baseline experiments can probe the presence of sterile neutrinos in a way that is different from, and complementary to, the probes of short-baseline experiments. We explore the question of how large sterile-active mixing angles need to be before long-baseline experiments can detect their effects, or how small they need to be before the interpretation of these experiments can safely disregard the possible existence of sterile neutrinos.

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arXiv2016

Probing CP violation with T2K, NO$ν$A and DUNE in the presence of non-unitarity

The presence of non-unitary neutrino mixing can affect the measurement of the three-neutrino leptonic Dirac CP phase and hamper efforts to probe CP violation due to degeneracies of the extra non-unitary CP phase with the standard CP phase. We study the effect of including non-unitarity on probing CP violation with the long-baseline experiments NO$ν$A, T2K and DUNE. We analyze the effect of non-unitary mixing at the level of oscillation probabilities associated with the relevant baselines, and present the CP violation sensitivity for the individual experiments and their combination. Our results show that there is an improvement in the CP violation sensitivity of the combination compared to the individual experiments.

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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.

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arXiv2016

Octant Degeneracy, Quadrant of CPV phase at Long Baseline $ν$ Experiments and Baryogenesis

In a recent work by two of 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 analyzed 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 leptogenesis can enhance the effect of resolving this entanglement, and how possible values of the leptonic CPV phase can be predicted in this context. Carrying out numerical analysis based on the recent updated experimental results for neutrino mixing angles, we predict the values of the leptonic CPV phase for 152 possible cases. We also confront our predictions of the leptonic CPV phase with the updated global fit and find that five values of $δ_{CP}$ are favoured by BAU constraints. One of the five values matches with the recent global fit value of $δ_{CP}$ (leptonic CPV phase) close to 1.41 $π$ in our model independent scenario. A detailed analytic and numerical study of baryogenesis through leptogenesis is performed in this framework in a model independent way.

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arXiv2015

Determining the Octant of $θ_{23}$ at LBNE in conjunction with Reactor Experiments

We have explored the possibilities of resolving the $θ_{23}$ octant degeneracy present in the newly planned Long-Baseline Neutrino Experiment (LBNE) by combining reactor data. Reactor experiments have already measured the third mixing angle $θ_{13}$ very precisely and this precise measurenent of $θ_{13}$ in turn helps in $θ_{23}$ octant measurement. We have examined the octant sensitivity with and without reactor data and it improves if reactor data is added. The comparative study of octant sensitivities of 10kt and 35kt liquid argon Far Detectors, with and without the Near Detector, reveals that the sensitivity increases with an increase in detector mass. Also, the presence of the Near Detector improves the sensitivity. The effect of adding priors on octant determination is also studied in this work.

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arXiv2015

Resolving Octant Degeneracy at LBL experiment by combining Daya Bay Reactor Setup

Long baseline Experiment (LBL) have promised to be a very powerful experimental set up to study various issues related to Neutrinos. Some ongoing and planned LBL and medium baseline experiments are - T2K, MINOS, NOvA, LBNE, LBNO etc. But the long baseline experiments are crippled due to presence of some parameter degeneracies, like the Octant degeneracy. In this work, we first show the presence of Octant degeneracy in LBL experiments, and then combine it with Daya Bay Reactor experiment, at different values of CP violation phase. We show that the Octant degeneracy in LBNE can be resolved completely with this proposal.

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arXiv2014

Probing CP violation at LBNE with reactor experiments

In this work, we have explored the possibilities of improving CP violation discovery potential of newly planned Long-Baseline Neutrino Experiment (LBNE), U.S.A., by combining with data from reactors. The third mixing angle $θ_{13}$ is now very precisely measured and this precise measurenent of $θ_{13}$ helps in measurement of CP violation. Here, CP violation is studied with and without data from reactors. Impact of placing a ND is also studied. It is found that CPV discovery potential of LBNE with ND increases when combined with data from reactors. With a far detector of 35 kt, it is possible to obtain 5$σ$ sensitivity of CPV when run for 5 years in $ν$ and 5 years in $\barν$ mode. When hierarchy is assumed to be normal hierarchy, CPV sensitivity is maximum. CPV discovery is possible by combining 5 years neutino data from LBNE with 3 years anti-neutrino from reactors. This study reveals that CPV can also be discovered at 5$σ$ cl in IH mode when appearance measurement of LBNE is combined with reactors.

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arXiv2012

Probing Sterile Neutrino Parameters with Double Chooz, Daya Bay and RENO

In this work, we present a realistic analysis of the potential of the present-day reactor experiments Double Chooz, Daya Bay and RENO for probing the existence of sterile neutrinos. We present exclusion regions for sterile oscillation parameters for each of these experiments, using simulations with realistic estimates of systematic errors and detector resolutions, and compare the sterile parameter sensitivity regions we obtain with the existing bounds from other reactor experiments. We find that these experimental set-ups give significant bounds on the parameter Θ_{ee} especially in the low sterile oscillation region 0.01 < Δm_{41}^2 < 0.05 eV^2. These bounds can add to our understanding of the sterile neutrino sector since there is still a tension in the allowed regions from different experiments for sterile parameters.

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