arXiv subjects

K. N. Deepthi

Publications and source records attributed to K. N. Deepthi.

At least 19 recordsLinked to original sources

arXiv2025

Probing new physics scenarios using high energy events at NOvA far detector

NuMI Off-axis $\nu_e$ Appearance (NOvA) experiment is an ongoing long baseline neutrino oscillation experiment. The primary channels of interest are the $\nu_e$, $\bar{\nu}_e$ appearance, $\nu_\mu$, $\bar{\nu}_\mu$ disappearance channels analyzed in the energy window $1< E_\nu < 4$ GeV. However, NOvA far detector sees non-trivial high energy $\nu_e$, $\bar{\nu}_e$ events in the energy range $4 < E_\nu < 20$ GeV. These high energy events provide us with an opportunity to investigate the subleading new physics scenarios. In this context, we study the sensitivity of the NOvA experiment to constrain the non-standard interaction (NSI) parameters and environmental decoherence. We observe that by including high energy events (signal + background) the degeneracy around $\epsilon_{e\tau} \sim 1.6$ can be removed throughout the $\delta_{CP}$ and $\delta_{e\tau}$ range. Further, we examine the role of signal versus beam background events in removing this degeneracy. In addition, we constrain the decoherence parameter $\Gamma$ considering events from $1<E_\nu<20$ GeV. Later, assuming the presence of decoherence in nature we obtain the allowed regions in $\theta_{23}$ and $\delta_{CP}$ plane.

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arXiv2025

The effect of non-standard interactions and environmental decoherence at DUNE

The Deep Underground Neutrino Experiment (DUNE) is a proposed long-baseline neutrino oscillation experiment that will project an on-axis wide-band neutrino beam over a distance of 1300 km to determine the unknowns in the neutrino sector. Given the baseline of 1300 km and the intense beam facility, DUNE is a promising experiment to study the sub-leading effects such as environmental decoherence, matter induced non-standard interactions (NSIs), neutrino decay, etc. In this study, we investigate how NSI and environmental decoherence affect the neutrino oscillation probabilities simultaneously. Considering the modified probabilities we obtain the updated mass hierarchy (MH) and CP violation (CPV) sensitivities of DUNE. Furthermore, we demonstrate the sensitivity of DUNE to distinguish between the effects of NSI and environmental decoherence.

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arXiv2024

Study of quantum decoherence at Protvino to ORCA experiment

Protvino to ORCA (Oscillation Research with Cosmics in the Abyss) (P2O) is an upcoming neutrino oscillation experiment with a very long baseline of 2595 km. Due to the substantial baseline, this experiment provides a unique opportunity to study the earth matter effects over very large distances. This makes it a suitable experiment to investigate the environmental decoherence in neutrino oscillations, where the neutrino system could interact with a stochastic environment and lead to a loss in the coherence of neutrino states. In this work, we consider an open quantum system framework to simulate the neutrino oscillations in P2O experiment and obtain bounds on the decoherence parameters in different phenomenological models. We assume that the decoherence parameter $\Gamma$ depends on neutrino energy $E_\nu$ as $\Gamma_{ij}(E_\nu) = \Gamma_{0} (\frac{E_\nu}{E_0})^n$. Further, we use these bounds to study the effect on the neutrino mass ordering sensitivity and CP violation sensitivity of P2O experiment.

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arXiv2023

Exploring the nature of neutrinos in a dissipative environment

In this study, we explore the scope of determining the neutrino nature in long-baseline neutrino oscillation experiments considering the effect of environmental decoherence in neutrino evolution. Assuming an open quantum system framework, we numerically analyze the two flavor neutrino oscillation probabilities. We observe that the transition probabilities accommodate the Majorana phase in the presence of dissipative environment. Considering this phenomenology, we study the effect of Majorana phase on these probabilities and investigate the sensitivity of T2K, ESSnuSB, NOvA, T2HKK and DUNE to differentiate between Dirac and Majorana neutrinos.

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arXiv2022

Vector leptoquark $U_3$ and CP violation at T2K, NOvA experiments

In the current epoch of neutrino physics, many experiments are aiming for precision measurements of oscillation parameters. Thus, various new physics scenarios which alter the neutrino oscillation probabilities in matter deserve careful investigation. In this context, we study the effect of a vector leptoquark which induces non-standard neutrino interactions (NSI) that modify the oscillation probabilities of neutrinos in matter. We show that such interactions provide a relatively large value of NSI parameter $\varepsilon_{e μ}$. Considering this NSI parameter, we successfully explain the recent discrepancy between the observed $δ_{CP}$ results of T2K and NOvA.

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arXiv2021

Constraining CPT violation with Hyper-Kamiokande and ESSnuSB

CPT invariance is one of the most fundamental symmetries in nature and it plays a major role in the formulation of Quantum Field Theory. Although no definitive signal of CPT violation has been observed so far, there are many reasons to carefully investigate various low-energy phenomena that can provide better probes to test CPT symmetry. In this context, neutrino experiments are expected to provide more stringent bounds on CPT invariance violation when compared to the existing bounds from the Kaon system. In this work, we investigate the sensitivity of the upcoming long-baseline experiments: Hyper Kamiokande (T2HK, T2HKK), ESSnuSB and DUNE to constrain the CPT violating parameters $Δ(δ_{CP})$, $Δ(m^2_{31})$ and $Δ(\sin^2 θ_{23})$, which characterize the difference between neutrino and antineutrino oscillation parameters. Further, we analyse neutrino and antineutrino data independently and constrain the oscillation parameters governing them by considering the combination of these experiments (DUNE+T2HKK and DUNE+ESSnuSB). In addition, assuming CPT symmetry is violated in nature, we study the individual ability of the aforementioned experiments to establish CPT violation. We found that the experiments Hyper-K (T2HK, T2HKK) and ESSnuSB, along with DUNE, will be able to establish CPT violation in their proposed run-times.

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arXiv2020

Implications of the Dark LMA solution and Fourth Sterile Neutrino for Neutrino-less Double Beta Decay

We analyze the effect of the Dark-large mixing angle (DLMA) solution on the effective Majorana mass ($m_{ββ}$) governing neutrino-less double beta decay ($0νββ$) in the presence of a sterile neutrino. We consider the 3+1 picture, comprising of one additional sterile neutrino. We have checked that the MSW resonance in the sun can take place in the DLMA parameter space in this scenario. Next we investigate how the values of the solar mixing angle $θ_{12}$ corresponding to the DLMA region alter the predictions of $m_{ββ}$ including a sterile neutrino in the analysis. We also compare our results with three generation cases for both standard large mixing angle (LMA) and DLMA. Additionally, we evaluate the discovery sensitivity of the future ${}^{136}Xe$ experiments in this context.

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arXiv2019

Exploring Partial $μ$-$τ$ Reflection Symmetry at DUNE and Hyper-Kamiokande

We study origin, consequences and testability of a hypothesis of `partial $μ$-$τ$' reflection symmetry. This symmetry predicts $ |U_{μi}|=|U_{τi}|~(i=1,2,3) $ for a single column of the leptonic mixing matrix $U$. Depending on whether this symmetry holds for the first or second column of $U$ different correlations between $θ_{23}$ and $ δ_{CP} $ can be obtained. This symmetry can be obtained using discrete flavour symmetries. In particular, all the subgroups of SU(3) with 3-dimensional irreducible representation which are classified as class C or D can lead to partial $μ$-$τ$ reflection symmetry. We show how the predictions of this symmetry compare with the allowed area in the $\sin^2θ_{23} - δ_{CP}$ plane as obtained from the global analysis of neutrino oscillation data. Furthermore, we study the possibility of testing these symmetries at the proposed DUNE and Hyper-Kamiokande (HK) experiments (T2HK, T2HKK), by incorporating the correlations between $θ_{23}$ and $ δ_{CP}$ predicted by the symmetries. We find that when simulated data of DUNE and HK is fitted with the symmetry predictions, the $θ_{23}-δ_{CP}$ parameter space gets largely restricted near the CP conserving values of $ δ_{CP} $. Finally, we illustrate the capability of these experiments to distinguish between the two cases leading to partial $μ-τ$ symmetry namely $|U_{\mu1}| = |U_{τ1}|$ and $|U_{μ2}| = |U_{τ2}|$.

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arXiv2017

Spotlighting the sensitivities of T2HK,T2HKK and DUNE

Neutrino oscillation physics has entered the precision era and the potential forthcoming experiments Hyper-Kamiokande and Deep Under-ground Neutrino Experiment (DUNE) are expected to lead this endeavor. In this paper we perform a comprehensive study of the octant, mass hierarchy and CP discovery sensitivities of DUNE, T2HK & T2HKK in their individual capacity and investigate the synergies of the aforementioned experiments with the on going T2K and NO$ν$A experiments. We present a comparative account of the probabilities at the three baselines and explore in detail the physics issues which can cause the discrepancies in the sensitivities among the different experiments. We also find out the optimal exposure required by these experiments for achieving $5σ$ hierarchy and octant sensitivity and to discover CP violation at $3σ$ for 60\% values of $δ_{CP}$. In addition we vary the neutrino-antineutrino runtime ratios for T2HK & T2HKK and check if the sensitivities are affected significantly due to this.

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arXiv2017

Challenges posed by non-standard neutrino interactions in the determination of $δ_{CP}$ at DUNE

One of the primary objectives of Deep Underground Neutrino Experiment (DUNE) is to discover the leptonic CP violation and to identify it's source. In this context, we study the impact of non-standard neutrino interactions (NSIs) on observing the CP violation signal at DUNE. We explore the impact of various parameter degeneracies introduced by non-zero NSI and identify which of these can influence the CP violation sensitivity and CP precision of DUNE, by considering NSI both in data and in theory. In particular, we study how the CP sensitivity of DUNE is affected because of the intrinsic hierarchy degeneracy which occurs when the diagonal NSI parameter $ε_{ee}=-1$ and $δ_{CP}= \pm 90^{\circ}$.

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arXiv2017

Can nonstandard interactions jeopardize the hierarchy sensitivity of DUNE ?

We study the effect of non-standard interactions (NSIs) on the propagation of neutrinos through the Earth matter and how it affects the hierarchy sensitivity of the DUNE experiment. We emphasize on the special case when the diagonal NSI parameter $ε_{ee} = -1$, nullifying the standard matter effect. We show that, if in addition, CP violation is maximal then this gives rise to an exact intrinsic hierarchy degeneracy in the appearance channel, irrespective of the baseline and energy. Introduction of off-diagonal NSI parameter, $ε_{e τ}$, shifts the position of this degeneracy to a different $ε_{ee}$. Moreover the unknown magnitude and phases of the off-diagonal NSI parameters can give rise to additional degeneracies. Overall, given the current model independent limits on NSI parameters, the hierarchy sensitivity of DUNE can get seriously impacted. However, a more precise knowledge on the NSI parameters, specially $ε_{ee}$, can give rise to an improved sensitivity. Alternatively, if NSI exists in nature, and still DUNE shows hierarchy sensitivity, certain ranges of the NSI parameters can be excluded. Additionally, we briefly discussed the implications of $ε_{ee} = -1$ (in the Earth) on MSW effect in the Sun.

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arXiv2017

Generalized degeneracies and their resolution in neutrino oscillation experiments

We discuss a comprehensive way to study the parameter degeneracies in the form of a generalized degeneracy in the neutrino oscillation experiments. First we describe the various degeneracies by considering only neutrino run of the long baseline experiment (LBL), NO$ ν$A. Then we discuss the role of antineutrinos. Later, we present the combined role of T2K (LBL experiment) and ICAL@INO (atmospheric experiment) to resolve these degeneracies. We also discuss the affect of new physics like non-standards interactions (NSI) on the determination of neutrino mass hierarchy in DUNE.

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arXiv2016

First measurement of electron neutrino appearance in NOvA

We report results from the first search for $ν_μ\toν_e$ transitions by the NOvA experiment. In an exposure equivalent to $2.74\times10^{20}$ protons-on-target in the upgraded NuMI beam at Fermilab, we observe 6 events in the Far Detector, compared to a background expectation of $0.99\pm0.11$ (syst.) events based on the Near Detector measurement. A secondary analysis observes 11 events with a background of $1.07\pm0.14$ (syst.). The $3.3σ$ excess of events observed in the primary analysis disfavors $0.1π< δ_{CP} < 0.5π$ in the inverted mass hierarchy at the 90% C.L.

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arXiv2016

A comprehensive study of the discovery potential of NOvA, T2K and T2HK experiments

With the recent measurement of reactor mixing angle $θ_{13}$ the knowledge of neutrino oscillation parameters that describe PMNS matrix has improved significantly except the CP violating phase $δ_{CP}$. The other unknown parameters in neutrino oscillation studies are mass hierarchy and the octant of the atmospheric mixing angle $θ_{23}$. Many dedicated experiments are proposed to determine these parameters which may take at least 10 years from now to become operational. It is therefore very crucial to use the results from the existing experiments to see whether we can get even partial answers to these questions. In this paper we study the discovery potential of the ongoing NO$ν$A and T2K experiments as well as the forthcoming T2HK experiment in addressing these questions. In particular, we evaluate the sensitivity of NO$ν$A to determine neutrino mass hierarchy, octant degeneracy and to obtain CP violation phase after running for its scheduled period of 3 years in neutrino mode and 3 years in anti-neutrino mode. We then extend the analysis to understand the discovery potential if the experiments will run for (5$ν$+5$\barν$) years and (7$ν$+3$\barν$) years. We also show how the sensitivity improves when we combine the data from (3$ν$+3$\barν$) years of NO$ν$A run with (3$ν$+2$\barν$) years of T2K and (3$ν$+7$\barν$) years of T2HK experiments. The CP violation sensitivity is marginal for T2K and NO$ν$A experiments even for ten years data taking of NO$ν$A. T2HK has a significance above 5$σ$ for a fraction of two-fifth values of the $δ_{CP}$ space. We also find that $δ_{CP}$ can be determined to be better than $35^\circ $, $21^\circ $ and $9^\circ $ for all values of $δ_{CP}$ for T2K, NO$ν$A and T2HK respectively.

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arXiv2016

First measurement of muon-neutrino disappearance in NOvA

This paper reports the first measurement using the NOvA detectors of $ν_μ$ disappearance in a $ν_μ$ beam. The analysis uses a 14 kton-equivalent exposure of $2.74 \times 10^{20}$ protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure $Δm^{2}_{32}=(2.52^{+0.20}_{-0.18})\times 10^{-3}$ eV$^{2}$ and $\sin^2θ_{23}$ in the range 0.38-0.65, both at the 68% confidence level, with two statistically-degenerate best fit points at $\sin^2θ_{23} = $ 0.43 and 0.60. Results for the inverted mass hierarchy are also presented.

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arXiv2015

Predicting Leptonic CP phase by considering deviations in charged lepton and neutrino sectors

Recently, the reactor mixing angle $θ_{13}$ has been measured precisely by Daya Bay, RENO and T2K experiments with a moderately large value. However, the standard form of neutrino mixing patterns such as bimaximal, tri-bimaximal, golden ratio of types A and B, hexagonal etc., which are based on certain flavor symmetries, predict vanishing $θ_{13}$. Using the fact that the neutrino mixing matrix can be represented as $V_{\rm PMNS}=U_l^{\dagger} U_νP_ν$, where $U_l$ and $U_ν$ result from the diagonalization of the charged lepton and neutrino mass matrices and $P_ν$ is a diagonal matrix containing Majorana phases, we explore the possibility of accounting for the large reactor mixing angle by considering deviations both in the charged lepton and neutrino sector. In the charged lepton sector we consider the deviation as an additional rotation in the (12) and (13) planes, whereas in neutrino sector we consider deviations to various neutrino mixing patterns through (13) and (23) rotations. We find that with the inclusion of these deviations it is possible to accommodate the observed large reactor mixing angle $θ_{13}$, and one can also obtain limits on the CP violating Dirac phase $δ_{CP}$ and Jarlskog invariant $J_{CP}$ for most of the cases. We then explore whether our findings can be tested in the currently running NO$ν$A experiment with 3 years of data taking in neutrino mode followed by 3 years with anti-neutrino mode.

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arXiv2015

Revisiting the sensitivity studies for leptonic CP violation and mass hierarchy with T2K, NOvA and LBNE experiments

Precision measurement of the neutrino mixing parameters and the determination of mass hierarchy are the primary goals of the present and upcoming neutrino experiments. In this work, we study the sensitivity of T2K,NO$ν$A and LBNE experiments to discover leptonic CP violation and the determination of neutrino mass hierarchy. We obtain the correlation between the CP violating phase $δ_{CP}$ and the mixing angles $θ_{13}$, $θ_{23}$ and the sensitivity to determine the octant of atmospheric mixing angle $θ_{23}$. The entire analysis is done for a total 10 years (5$ν$+ 5$\bar ν$) of running of T2K, NO$ν$A and LBNE experiments. Furthermore, we also consider the impact of cross section uncertainties on the CP violation sensitivity of LBNE experiment.

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arXiv2013

Charged lepton correction to tribimaximal lepton mixing and its implications to neutrino phenomenology

The recent results from Daya Bay and RENO reactor neutrino experiments have firmly established that the smallest reactor mixing angle $θ_{13}$ is non-vanishing at the $5 σ$ level, with a relatively large value, i.e., $θ_{13}\approx 9^{\circ}$. Using the fact that the neutrino mixing matrix can be represented as $V_{\rm PMNS}=U_l^{\dagger} U_ν P_ν$, where $U_l$ and $U_ν$ result from the diagonalization of the charged lepton and neutrino mass matrices and $P_ν$ is a diagonal matrix containing the Majorana phases and assuming the tri-bimaximal form for $U_ν$, we investigate the possibility of accounting for the large reactor mixing angle due to the corrections of the charged lepton mixing matrix. The form of $U_{l}$ is assumed to be that of CKM mixing matrix of the quark sector. We find that with this modification it is possible to accommodate the large observed reactor mixing angle $θ_{13}$. We also study the implications of such corrections on the other phenomenological observables.

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