arXiv subjects

Debajyoti Dutta

Publications and source records attributed to Debajyoti Dutta.

At least 19 recordsLinked to original sources

arXiv2026

Resolving Lorentz-Violating New Physics at ESSnuSB Using High-Statistics Complementarity with T2HK

A primary objective for next-generation long-baseline neutrino facilities is the search for Planck-scale Lorentz Invariance Violation (LIV). In this work, we explore the capabilities of the proposed ESSnuSB and T2HK experiments to constrain isotropic, CPT-violating LIV parameters ($a_{\alpha\beta}$). The modifications to oscillation probabilities induced by these LIV parameters can introduce parameter degeneracies with the atmospheric mixing angle $\theta_{23}$ and the Dirac CP-violating phase $\delta_{CP}$, which can potentially result in incorrect determination of the said standard oscillation parameters if we do not account for LIV effects. Through detailed GLoBES simulations, we find that while the second-oscillation-maximum configuration of ESSnuSB yields good constraints on the exact phase of $\delta_{CP}$, its intrinsic neutrino-antineutrino statistical asymmetry persistently leads to wrong octant fake solutions for $\theta_{23}$. By synergizing ESSnuSB's 360 km and 540 km baselines with the complementary, high-statistics measurements from first-maximum configuration of the T2HK's 295 km baseline, we show that the degeneracies are resolved for most LIV parameters. Our analysis reflects how complementarity between ESSnuSB and T2HK provides an effective, matter-independent framework to break LIV-induced degeneracies and establish bounds on Planck-scale LIV physics.

hep-ph↗

arXiv2026

Testing residual-symmetry-fixed columns of $U_{\rm PMNS}$ at DUNE and T2HK with initial JUNO constraints

We study fixed-column predictions of the lepton mixing matrix that arise from residual symmetries originating in a class of discrete flavour and modular symmetries. While the recent high-precision determination of $\sin^{2}\theta_{12}$ by JUNO already constrains part of these predictions, the remaining ones are primarily characterized by non-trivial correlations between $\sin^{2}\theta_{23}$ and the Dirac CP phase $\delta_{\rm CP}$, which are currently only weakly constrained. This motivates a detailed investigation using next-generation long-baseline neutrino experiments. For the viable scenarios, we derive precise $\sin^{2}\theta_{23}$-$\delta_{\rm CP}$ correlations and use them to generate test-event samples, marginalising over the remaining oscillation parameters. We perform detailed simulations for DUNE and T2HK, presenting allowed regions in the $\sin^{2}\theta_{23}$-$\delta_{\rm CP}$ plane and evaluating the CP-violation fraction as a function of exposure. Our results show that the combined sensitivity of DUNE and T2HK provides a robust test of fixed-column lepton-mixing predictions.

hep-ph↗

arXiv2026

Neutrino texture-zeros after JUNO's first results: Implications for long-baseline neutrino experiments

The recent results from the JUNO reactor neutrino experiment have significantly improved our knowledge of the solar mixing angle $θ_{12}$ and the solar mass splitting $Δm^2_{21}$. We study the impact of these improved estimates on the validity of texture-zeros in the light neutrino mass matrix by assuming neutrinos to be of Majorana nature. Considering a diagonal charged lepton basis, we revisit the previously allowed one-zero and two-zero textures and check their validity by using updated neutrino data from JUNO. While JUNO data rule out one previously allowed two-zero texture, they also make predictions for other neutrino parameters more precise. We finally study the prospects of probing the currently allowed texture-zeros and their predicted correlations among neutrino parameters at the Deep Underground Neutrino Experiment (DUNE). The inclusion of JUNO and reactor experiments strengthens DUNE's ability to constrain the allowed parameter space of both one-zero and two-zero textures. We also observe that DUNE benefits substantially from the complementarity with the T2HK experiment.

hep-ph↗

arXiv2025

Neutrino Textures from Modular $A_4$ Left--Right Symmetry: Experimental Signatures at DUNE and T2HK in the Post-JUNO Era

We have realized different two-zero textures within the framework of the left right symmetric model using the $Γ_{3}\cong A_{4}$ modular group. The matter multiplets of the model are assigned as three singlet representations of the $A_{4}$ group, and their charge assignments together with the modular weights of the Yukawa couplings are chosen in such a way that different two-zero textures of the neutrino mass matrix are obtained. In total, we have successfully realized seven different two-zero textures. Furthermore, we have studied neutrinoless double beta decay and lepton flavor violating (LFV) processes, and have calculated the effective Majorana mass and the branching ratios for LFV processes for each of the textures. We further probe these two-zero textures at the long-baseline neutrino experiments DUNE and T2HK. We find that DUNE, especially when combined with T2HK, can significantly restrict the $θ_{23}-δ_{\rm CP}$ parameter space predicted by these textures. Moreover, the inclusion of high-precision determinations of $θ_{12}$ (from JUNO) and $θ_{13}$ leads to a substantial, further reduction of the allowed parameter space. For assumed inverted mass ordering, the synergy of DUNE and T2HK leads to a highly predictive scenario for the $B_{2}$ and $B_{4}$ textures, as the allowed regions collapse into tiny islands near the CP-conserving points in the lower and higher octant of $θ_{23}$, respectively.

hep-ph↗

arXiv2025

Constraining and Resolving Lorentz-Violating New Physics at ESSnuSB Using Complementarity with DUNE

We examine the sensitivity of the ESSnuSB and DUNE long-baseline neutrino experiments to isotropic, CPT-violating Lorentz Invariance Violation (LIV). Using detailed simulations for the 360 km and 540 km ESSnuSB baselines and the 1300 km DUNE setup, we assess how LIV parameters influence oscillation probabilities, event spectra, and degeneracies among oscillation parameters. We find that LIV-induced modifications can closely mimic variations in $θ_{23}$ and $δ_{\rm CP}$, potentially leading to incorrect determination of the atmospheric mixing angle octant and the leptonic CP phase if LIV effects are not accounted for. Although combining the two ESSnuSB baselines improves overall sensitivity, it does not fully remove these degeneracies. In contrast, a joint ESSnuSB+DUNE analysis benefiting from the synergy between second-maximum sensitivity at ESSnuSB and first-maximum, matter-enhanced sensitivity at DUNE can successfully resolve all these degeneracies and can yield significantly stronger constraints on all the LIV parameters. The results presented here highlights the essential role of multi-baseline, multi-energy experimental strategies to probe Planck-suppressed Lorentz-violating new physics.

hep-ph↗

arXiv2024

Neutrino mass ordering sensitivities at DUNE, HK and KNO in presence of scalar NSI

The limitations of the Standard Model in explaining neutrino masses and neutrino mixing lead to the exploration of frameworks beyond the Standard Model (BSM). The possibility of neutrinos interacting with fermions via a scalar mediator is one of the interesting prospects. The study of neutrino non-standard interactions (NSI) is a well-motivated phenomenological scenario to explore new physics beyond the Standard Model. These new interactions may alter the standard neutrino oscillation probabilities, potentially leading to observable effects in experiments. It also allows for the exploration of absolute neutrino masses via oscillation experiments. It can modify the oscillation probabilities, which in turn can affect the physics sensitivities in long-baseline experiments. The linear scaling of the effects of scalar NSI with matter density also motivates its exploration in long-baseline (LBL) experiments. We will present our study on the impact of a scalar-mediated NSI on the mass ordering (MO) sensitivities of three long-baseline neutrino experiments, i.e., DUNE, HK and KNO. We study the impact on MO sensitivities at these experiments assuming that scalar NSI parameters are present in nature and are known from other non-LBL experiments. The presence of scalar NSI can notably impact the MO sensitivities of these experiments. Furthermore, we analyze the potential synergy by combining data from DUNE with HK and HK+KNO, thereby exploring a broader parameter space.

hep-ph↗

arXiv2024

Synergy between DUNE and T2HKK to probe Invisible Neutrino Decay

We address the consequence of invisible neutrino decay within the framework of two long base-line neutrino experiments: T2HKK (Tokai-to-Hyper-Kamiokande-to-Korea) and DUNE (Deep Underground Neutrino experiment). Our primary objective is to bring out the aspects of CC (charged current) and NC (neutral current) measurements at DUNE in the context of invisible neutrino decay. We find that the inclusion of NC measurements with the CC measurements enhances its ability to constrain invisible neutrino decay. Further, the synergy between DUNE and T2HKK improves the constraints on invisible neutrino decay. At 3$σ$ C.L. (confidence level) the derived constraint is $τ_{3}/m_{3}\geq6.21\times10^{-11}$ s/eV. Additionally, if nature prefers $ν_{3}$ to be unstable and the decay width is $τ_{3}/m_{3}= 2.2\times10^{-11}$ s/eV, this combination can exclude the no-decay scenario at more than 5$σ$ C.L. Although the CP sensitivity is not much hindered in the presence of invisible neutrino decay, the measurements of $θ_{23}$ and the ability to resolve octant of $θ_{23}$ is significantly influenced in these individual experiments. In the presence of invisible neutrino decay, the synergy between DUNE and T2HKK can exclude the wrong octant somewhat more effectively than either experiment alone.

hep-ph↗

arXiv2024

Impact of scalar NSI on the neutrino mass ordering sensitivity at DUNE, HK and KNO

The study of neutrino non-standard interactions (NSI) is a well-motivated phenomenological scenario to explore new physics beyond the Standard Model. The possible scalar coupling of neutrinos ($ν$) with matter is one of such new physics scenarios that appears as a sub-dominant effect that can impact the $ν$-oscillations in matter. The presence of scalar NSI introduces an additional contribution directly to the $ν$-mass matrix in the interaction Hamiltonian and subsequently to the $ν$-oscillations. This indicates that scalar NSI may have a significant impact on measurements related to $ν$-oscillations e.g. leptonic CP phase $(δ_{CP})$, $θ_{23}$ octant and neutrino mass ordering (MO). The linear scaling of the effects of scalar NSI with matter density also motivates its exploration in long-baseline (LBL) experiments. In this paper, we study the impact of a scalar-mediated NSI on the MO sensitivity of DUNE, HK and HK+KNO, which are upcoming LBL experiments. We study the impact on MO sensitivities at these experiments assuming that scalar NSI parameters are present in nature and is known from other non-LBL experiments. We observe that the presence of diagonal scalar NSI elements can significantly affect the $ν$-mass ordering sensitivities. We then also combine the data from DUNE with HK and HK+KNO to explore possible synergy among these experiments in a wider parameter space. We also observe a significant enhancement in the MO sensitivities for the combined analysis.

hep-ph↗

arXiv2023

Imprints of scalar NSI on the CP-violation sensitivity using synergy among DUNE, T2HK and T2HKK

The Non-Standard Interactions (NSIs) are subdominant effects, often appearing in various extensions of SM, which may impact the neutrino oscillations through matter. It is important and interesting to explore the impact of NSIs in the ongoing and upcoming precise neutrino oscillations experiments. In this work, we have studied the imprints of a scalar-mediated NSI in three upcoming long-baseline (LBL) experiments (DUNE, T2HK, T2HKK). The effects of scalar NSI appears as a medium-dependent correction to the neutrino mass term. Its contribution scales linearly with matter density, making LBL experiments a suitable candidate to probe its effects. We show that the scalar NSI may significantly impact the oscillation probabilities, event rates at the detectors and the $χ^2$-sensitivities of $δ_{CP}$ measurements. We present the results of a combined analysis involving the LBL experiments (DUNE+T2HK, DUNE+T2HKK, DUNE+T2HK+T2HKK) which offer a better capability of constraining the scalar NSI parameters as well as an improved sensitivity towards CP-violation.

hep-ph↗

arXiv2022

Sterile Neutrinos: Propagation in Matter and Sensitivity to Sterile Mass Ordering

We analytically calculate the neutrino conversion probability $P_{μe}$ in the presence of sterile neutrinos, with exact dependence on $Δm^2_{41}$ and with matter effects explicitly included. Using perturbative expansion in small parameters, the terms involving the small mixing angles $θ_{24}$ and $θ_{34}$ can be separated out, with $θ_{34}$ dependence only arising due to matter effects. We express $P_{μe}$ in terms of the quantities of the form $\sin(x)/x$, which helps in elucidating its dependence on matter effects and a wide range of $Δm^2_{41}$ values. Our analytic expressions allow us to predict the effects of the sign of $Δm^2_{41}$ at a long baseline experiment like DUNE. We numerically calculate the sensitivity of DUNE to the sterile mass ordering and find that this sensitivity can be significant in the range $|Δm^2_{41}| \sim (10^{-4} - 10^{-2})$ eV$^2$, for either mass ordering of active neutrinos. The dependence of this sensitivity on the value of $Δm^2_{41}$ for all mass ordering combinations can be explained by investigating the resonance-like terms appearing due to the interplay between the sterile sector and matter effects.

hep-ph↗

arXiv2022

Exploring the effects of Scalar Non Standard Interactions on the CP violation sensitivity at DUNE

The Neutrino oscillations have provided an excellent opportunity to study new-physics beyond the Standard Model, popularly known as BSM. The unknown couplings involving neutrinos, termed non-standard interactions (NSI), may appear as `new-physics' in different neutrino experiments. The neutrino NSI offers significant effects on neutrino oscillations and CP-sensitivity, which may be probed in various neutrino experiments. The idea of neutrinos coupling with a scalar has evolved recently and looks promising. The effects of scalar NSI may appear as a perturbation to the neutrino mass matrix in the neutrino Hamiltonian. It modifies the neutrino mass matrix and may provide a direct possibility of probing neutrino mass models. As the scalar NSI affects the neutrino mass matrix in the Hamiltonian, its effect is energy independent. Moreover, the matter effects due to scalar NSI scales linearly with the matter density. In this work, we have performed a model-independent study of the effects of scalar NSI at long baseline neutrino experiments, taking DUNE as a case study. We have performed such a thorough study for DUNE for the first time. Various neutrino parameters may get affected due to the inclusion of scalar NSI as it modifies the effective mass matrix of neutrinos. We have explored the impact of scalar NSI in neutrino oscillations and its impact on the measurements of various mixing parameters. We have probed the effects of scalar NSI on different oscillation channels relevant to the experiment. We have also explored the impact of various possible elements in the scalar NSI term on the CP-violation sensitivity at DUNE.

hep-ph↗

arXiv2021

Non-Unitarity at DUNE and T2HK with Charged and Neutral Current Measurements

Neutral current (NC) measurements play an important role in exploring new physics scenarios at long-baseline neutrino oscillation experiments. We find that combining NC measurements of the proposed Deep Underground Neutrino Experiment (DUNE) with its charged current (CC) measurements enhances the bounds on some of the Non-Unitarity (NU) parameters. Combining DUNE with the T2HK experiment improves the bounds further. We show that even in the averaged out regime of light sterile neutrinos, the NC events are different from the heavy sterile case in the leading order. It is observed that NC measurements at DUNE provide much better constraints on the $α_{33}$ parameter than the CC measurements.

hep-ph↗

arXiv2020

Invisible neutrino decay : First vs second oscillation maximum

We study the physics potential of the long-baseline experiments T2HK, T2HKK and ESS$ν$SB in the context of invisible neutrino decay. We consider normal mass ordering and assume that the state $ν_{3}$ as unstable, decaying into sterile states during the flight and obtain constraints on the neutrino decay lifetime ($τ_3$). We find that T2HK, T2HKK and ESS$ν$SB are sensitive to the decay-rate of $ν_{3}$ for $τ_{3}/m_{3} \leq 2.72\times10^{-11}$s/eV, $τ_{3}/m_{3} \leq 4.36\times10^{-11}$s/eV and $τ_{3}/m_{3} \leq 2.43\times10^{-11}$s/eV respectively at 3$σ$ C.L. We compare and contrast the sensitivities of the three experiments and specially investigate the role played by the mixing angle $θ_{23}$. It is seen that for experiments with flux peak near the second oscillation maxima, the poorer sensitivity to $θ_{23}$ results in weaker constraints on the decay lifetime. Although, T2HKK has one detector close to the second oscillation maxima, having another detector at the first oscillation maxima results in superior sensitivity to decay. In addition, we find a synergy between the two baselines of the T2HKK experiment which helps in giving a better sensitivity for $θ_{23}$ in the higher octant. We discuss the octant sensitivity in presence of decay and show that there is an enhancement in sensitivity which occurs due to the contribution from the survival probability $P_{μμ}$ which is more pronounced for the experiments at the second oscillation maxima. We also obtain the combined sensitivity of T2HK+ESS$ν$SB and T2HKK+ESS$ν$SB as $τ_{3}/m_{3} \leq 4.36\times10^{-11}$s/eV and $τ_{3}/m_{3} \leq 5.53\times10^{-11}$s/eV respectively at 3$σ$ C.L.

hep-ph↗

arXiv2019

Exploring fake solutions in the sterile neutrino sector at long-baseline experiments

Active-sterile neutrino mixing is known to affect the neutrino oscillation probabilities at both short as well as long-baselines. In particular, constraints on active-sterile neutrino oscillation parameters can be obtained from long-baseline experiments such as T2HK and DUNE. We present here existence of fake solution in the appearance channel for the 3+1 scenario at long-baseline experiments. We show that the appearance probability is same for values of $Δm_{41}^2$ for which the fast oscillations are averaged out and for $Δm_{41}^2=(1/2)Δm_{31}^2$. The fake solution does not appear for the disappearance channel.

hep-ph↗

arXiv2018

Measuring the Sterile Neutrino CP Phase at DUNE and T2HK

The CP phases associated with the sterile neutrino cannot be measured in the dedicated short-baseline experiments being built to test the sterile neutrino hypothesis. On the other hand, these phases can be measured in long-baseline experiments, even though the main goal of these experiments is not to test or measure sterile neutrino parameters. In particular, the sterile neutrino phase $δ_{24}$ affects the charged-current electron appearance data in long-baseline experiment. In this paper we show for the first time how well the sterile neutrino phase $δ_{24}$ can be measured by the next-generation long-baseline experiments DUNE, T2HK (and T2HKK). We also show the expected precision with which this sterile phase can be measured by combining the DUNE data with data from T2HK or T2HKK. We also present the sensitivity of these experiments to the sterile mixing angles, both by themselves, as well as when DUNE is combined with T2HK or T2HKK.

hep-ph↗

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 $\sin^{2}θ_{23}$.

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

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.

hep-ph↗