arXiv subjects

Sanjib Kumar Agarwalla

Publications and source records attributed to Sanjib Kumar Agarwalla.

At least 19 recordsLinked to original sources

arXiv2026

Deep Earth imaging through neutrino and seismic tomography

This article is a report on the Deep Earth Neutrino + Seismic Imaging and TomographY (DENSITY 2026) mini-workshop, held on 23--24 February 2026 in the Department of Earth and Climate Science at the Indian Institute of Science Education and Research (IISER), Pune. The workshop was jointly organised by IISER Pune and the Institute of Physics (IOP), Bhubaneswar. Researchers from Earth Sciences and Neutrino Physics participated in the workshop to explore multipronged approaches for studying the deep interior of the Earth. Since the participants came from diverse scientific disciplines (seismology, geochemistry, mineral physics, and neutrino physics), the programme featured a series of overview talks introducing all participants to the basic concepts of each field and highlighting how these concepts may be applied to the study of the deep Earth.

hep-ex↗

arXiv2026

$δ_{CP}$-free constraints on NSI parameters $\varepsilon_{eμ}$ and $\varepsilon_{eτ}$ using high-purity $ν_μ$ CC events at IceCube DeepCore

Atmospheric neutrinos provide a unique avenue to probe theories beyond the Standard Model (BSM) over a wide range of energies and path lengths. The theory of nonstandard interactions (NSI) of neutrinos is one of the important BSM scenarios, which can modify flavor oscillations of atmospheric neutrinos traveling through the Earth. In this work, we use a high-purity $ν_μ$ charged-current (CC) sample of atmospheric neutrinos from IceCube DeepCore with a livetime of 7.5 years to search for the NSI parameters $\varepsilon_{eμ}$, $\varepsilon_{eτ}$, and $\varepsilon_{ee}-\varepsilon_{μμ}$. The $ν_μ$ CC events mainly come from the $ν_μ$ survival channel having no significant dependence on $δ_{CP}$. Therefore, the constraints on $\varepsilon_{eμ}$ and $\varepsilon_{eτ}$ obtained using this $ν_μ$ CC sample are expected to be free from the $δ_{CP}$-degeneracy. The data sample is found to be in agreement with the standard neutrino interactions. Therefore, we place bounds on these NSI parameters that are consistent with and comparable to existing experimental constraints. These $δ_{CP}$-free constraints from IceCube DeepCore are complementary to those from the long-baseline neutrino oscillation experiments, where the appearance channel depends on $δ_{CP}$.

hep-ph↗

arXiv2026

New constraints on non-unitary neutrino mixing from 8 years of IceCube DeepCore atmospheric neutrino data

The mixing between flavor and mass eigenstates of active neutrinos is described by a $3\times3$ unitary matrix. However, the presence of additional heavy sterile neutrino states can lead to a non-unitary neutrino mixing scenario. Atmospheric neutrinos, with their wide range of baselines and energies, provide an excellent probe of such effects. In particular, Earth matter effects in neutrino oscillations play an important role, as the neutral-current potential contributes non-trivially in the presence of non-unitarity. In this work, we use 8 years of publicly available atmospheric neutrino data of IceCube DeepCore to probe this non-unitary neutrino mixing scenario. This high-purity $ν_μ$ CC sample provides strong sensitivity, especially to the non-unitary parameters appearing at leading order in the $ν_μ\rightarrow ν_μ$ channel. The data sample is found to be consistent with the standard unitary mixing framework with no significant deviation. Using this data sample, we place the most stringent bound to date of $α_{33} > -0.027$ at 90% CL, while the other non-unitary parameters are constrained at competitive levels.

hep-ph↗

arXiv2026

Constraints on long-range neutrino interactions from a variety of $U(1)^\prime$ symmetries using atmospheric neutrinos at IceCube DeepCore

Neutrino oscillation experiments provide a unique probe to search for the physics beyond the Standard Model. In this work, we search for a broad class of anomaly-free flavor-dependent $U(1)^\prime$ symmetries using atmospheric neutrino data for the first time. Gauging these $U(1)^\prime$ symmetries give rise to ultra-light vector gauge bosons mediating long-range interactions (LRI) of neutrinos. These new interactions are sourced by the matter present in local and distant Universe, which can affect oscillations of neutrinos passing through the Earth. We use 8 years of high-purity $ν_μ$ charged-current neutrino events from IceCube DeepCore to search for these new interactions. We find no evidence for such new interactions in the data sample and place stringent constraints on the corresponding LRI potentials. These results are also translated as the bounds on the coupling strength and mass of mediator over their wide ranges for a plethora of $U(1)^\prime$ symmetries.

hep-ph↗

arXiv2026

Constraining the core radius and density jumps inside Earth using atmospheric neutrino oscillations

Atmospheric neutrinos probe the interior of Earth using weak interactions, and provide information complementary to that of gravitational and seismic measurements. While passing through Earth, multi-GeV neutrinos encounter matter effects due to the coherent forward scattering with ambient electrons, which alter the neutrino oscillation probabilities. These matter effects depend upon the density distribution of electrons inside Earth, and hence, can be used to determine the internal structure of Earth. In this work, we employ a five-layered model of Earth where the layer densities and radii are modified, keeping the mass and moment of inertia of Earth unchanged and respecting the hydrostatic equilibrium condition. We use the proposed INO-ICAL detector as an example of an atmospheric neutrino experiment that can distinguish between neutrinos and antineutrinos efficiently in the multi-GeV energy range. Our analyses demonstrate that such an experiment can simultaneously constrain density jumps inside Earth and locate the core-mantle boundary. The charge identification (CID) capability of the ICAL detector would play a crucial role in obtaining these correlated constraints. An ICAL-like detector without CID capability would also be able to perform this task, albeit with a reduced sensitivity.

hep-ph↗

arXiv2026

First Constraints on Long-Range Neutrino Interactions using IceCube DeepCore

We present the first search for new flavor-dependent long-range interactions (LRI) of neutrinos using publicly available 8 years of high-purity $ν_μ$ CC data from IceCube DeepCore. These interactions are mediated by ultra-light gauge bosons with masses below $10^{-10}$ eV, which can arise due to a new lepton-number gauge symmetry, such as $L_e - L_μ$ or $L_e - L_τ$. These long-range interactions induce matter potential between neutrinos and abundant electrons present in distant astrophysical sources. These LRI potentials could modify neutrino oscillation probabilities. By probing the effects of LRI on atmospheric neutrino oscillations at IceCube DeepCore, we place world-leading constraints on the coupling strength of these interactions.

hep-ph↗

arXiv2025

Stringent constraints on non-standard neutrino interactions using high-purity $ν_μ$ CC events in IceCube DeepCore

The neutral-current (NC) non-standard interactions (NSI) of neutrinos with fermions can modify the flavor oscillations of atmospheric neutrinos as they propagate through the Earth. We present constraints on the NC-NSI parameters $\varepsilon_{μτ}$ and $\varepsilon_{ττ}-\varepsilon_{μμ}$ (one at a time) using a high-purity sample of $ν_μ$ charged-current (CC) atmospheric neutrino events collected by IceCube DeepCore over 7.5 years of livetime. These two parameters significantly affect the $ν_μ$ disappearance channel for which this golden event sample is optimized by the IceCube Collaboration. The best fit to this dataset is consistent with no NSI hypothesis, and we place the most stringent constraints to date: $-\,0.0094 < \varepsilon_{μτ} < 0.0079$ and $-\,0.030 < \varepsilon_{ττ}-\varepsilon_{μμ} < 0.029$ at 90% confidence level.

hep-ph↗

arXiv2025

Probing Earth's core using atmospheric neutrino oscillations in the presence of NSI at INO-ICAL

Neutrinos can serve as a complementary and independent tool to gravitational and seismic studies in exploring the interior of Earth, thanks to their unique properties: extremely low interaction cross sections and flavor oscillations. With the precise measurements of neutrino oscillation parameters and observation of the non-zero value of mixing angle $θ_{13}$, it has become feasible to detect the forward scattering of GeV-energy atmospheric neutrinos passing through Earth with ambient electrons in the form of matter effects on neutrino oscillation probabilities. These matter effects depend on both the neutrino energy and electron density distribution along their path, making them ideally suited for exploring the inner structure of Earth. Furthermore, in the presence of non-standard interactions (NSI) of neutrinos with matter, oscillation patterns undergo additional modifications. In this study, we quantify the capability of an atmospheric neutrino experiment, such as a magnetized iron calorimeter detector, to validate the Earth's core and measure the position of the core-mantle boundary in the presence of NSI. We perform this study considering a three-layered density profile of Earth. Our analysis demonstrates that neutrino non-standard interactions impact these Earth tomography measurements in comparison to standard interactions.

hep-ph↗

arXiv2025

A White Paper on The Multi-Messenger Science Landscape in India

The multi-messenger science using different observational windows to the Universe such as Gravitational Waves (GWs), Electromagnetic Waves (EMs), Cosmic Rays (CRs), and Neutrinos offer an opportunity to study from the scale of a neutron star to cosmological scales over a large cosmic time. At the smallest scales, we can explore the structure of the neutron star and the different energetics involved in the transition of a pre-merger neutron star to a post-merger neutron star. This will open up a window to study the properties of matter in extreme conditions and a guaranteed discovery space. On the other hand, at the largest cosmological scales, multi-messenger observations allow us to study the long-standing problems in physical cosmology related to the Hubble constant, dark matter, and dark energy by mapping the expansion history of the Universe using GW sources. Moreover, the multi-messenger studies of astrophysical systems such as white dwarfs, neutron stars, and black holes of different masses, all the way up to a high redshift Universe, will bring insightful understanding into the physical processes associated with them that are inaccessible otherwise. This white paper discusses the key cases in the domain of multi-messenger astronomy and the role of observatories in India which can explore uncharted territories and open discovery spaces in different branches of physics ranging from nuclear physics to astrophysics.

astro-ph.HE↗

arXiv2025

A plethora of long-range neutrino interactions probed by DUNE and T2HK

The next-generation neutrino oscillation experiments would be sensitive to the new neutrino interactions that would strengthen the search for physics beyond the Standard Model. In this context, we explore the capabilities of the two leading future long-baseline neutrino oscillation experiments, DUNE and T2HK, to search for new flavor-dependent neutrino interactions with electrons, protons, and neutrons that could potentially modify neutrino flavor transitions. We forecast their sensitivities in the context of long-range neutrino interactions mediated by a neutral vector boson lighter than $10^{-10}$ eV and sourced by the vast amount of nearby and distant matter in the Earth, Moon, Sun, Milky Way, and local Universe. For the first time, we explore a plethora of $U(1)^\prime$ symmetries inducing the new interactions built from the combination of lepton and baryon numbers. We find that in all cases, DUNE and T2HK may constrain or discover the existence of new long-range neutrino interaction, and in some favorable cases, may identify the new $U(1)^\prime$ symmetry responsible for it. In this short proceeding, we only summarize the prospects of constraining the new interaction in case of all our candidate $U(1)^\prime$ symmetries, which have been discussed in JHEP 09 (2024) 055.

hep-ph↗

arXiv2025

Constraints on flavor-dependent long-range interactions of high-energy astrophysical neutrinos

Astrophysical neutrinos with energy in the TeV-PeV range traverse megaparsecs (Mpc) to gigaparsecs (Gpc) scale distances before they reach the Earth. Tiny physics effects that get accumulated over these large propagation paths during their journey may become observable at the detector. If there is some new interaction between neutrinos and the background matter, that can potentially affect the propagation of the astrophysical neutrinos. One such possible case is the flavor-dependent long-range interaction of neutrinos, which can affect the standard neutrino flavor transition, modifying the flavor composition of the astrophysical neutrinos at Earth. Using the present-day and future projection of the flavor-composition measurements of IceCube and IceCube-Gen2 along with the present and future measurement of the oscillation parameters, we explore the sensitivity of these experiments to probe long-range neutrino interaction with matter.

hep-ph↗

arXiv2025

Flavor-Dependent Long-Range Neutrino Interactions in DUNE and T2HK: Synergy Breeds Power

Discovering new neutrino interactions would provide evidence of physics beyond the Standard Model. We focus on flavor-dependent long-range neutrino interactions mediated by ultra-light mediators (masses below $10^{-10}$ eV) from lepton-number gauge symmetries $L_e-L_μ$, $L_e-L_τ$, and $L_μ-L_τ$. These interactions, sourced by electrons and neutrons in the Earth, Moon, Sun, Milky Way, and the local Universe, could modify neutrino oscillation probabilities. The upcoming long-baseline experiments, DUNE and T2HK, with their large statistics, reduced systematic uncertainties, and well-characterized neutrino beams, will probe these interactions. We forecast that, while individually DUNE and T2HK could constrain these long-range neutrino interactions, their combination lifts parameter degeneracies that weaken individual sensitivity and provides stronger constraints.

hep-ph↗

arXiv2025

Exploring constraints on the core radius and density jumps inside Earth using atmospheric neutrino oscillations

Atmospheric neutrinos, through their weak interactions, can serve as an independent tool for exploring the internal structure of Earth. The information obtained would be complementary to that provided by seismic and gravitational measurements. The Earth matter effects in neutrino oscillations depend upon the energy of neutrinos and the electron density distribution that they encounter during their journey through Earth, and hence, can be used to probe the inner structure of Earth. In this contribution, we demonstrate how well an atmospheric neutrino experiment, such as an iron calorimeter detector (ICAL), would simultaneously constrain the density jumps inside Earth and determine the location of the core-mantle boundary. In this work, we employ a five-layered density model of Earth, where the layer densities and core radius are modified to explore the parameter space, ensuring that the mass and moment of inertia of Earth remain constant while satisfying the hydrostatic equilibrium condition. We further demonstrate that the charge identification capability of an ICAL-like detector would play a crucial role in obtaining these correlated constraints.

hep-ph↗

arXiv2024

Constraining non-unitary neutrino mixing using matter effects in atmospheric neutrinos at INO-ICAL

The mass-induced neutrino oscillation is a well established phenomenon that is based on the unitary mixing among three light active neutrinos. Remarkable precision on neutrino mixing parameters over the last decade or so has opened up the prospects for testing the possible non-unitarity of the standard 3$ν$ mixing matrix, which may arise in the seesaw extensions of the Standard Model due to the admixture of three light active neutrinos with heavy isosinglet neutrinos. Because of this non-unitary neutrino mixing (NUNM), the oscillation probabilities among the three active neutrinos would be altered as compared to the probabilities obtained assuming a unitary 3$ν$ mixing matrix. In such a NUNM scenario, neutrinos can experience an additional matter effect due to the neutral current interactions with the ambient neutrons. Atmospheric neutrinos having access to a wide range of energies and baselines can experience a significant modifications in Earth's matter effect due to NUNM. In this paper, we study in detail how the NUNM parameter $α_{32}$ affects the muon neutrino and antineutrino survival probabilities in a different way. Then, we place a comparable and complementary constraint on $α_{32}$ in a model independent fashion using the proposed 50 kt magnetized Iron Calorimeter (ICAL) detector under the India-based Neutrino Observatory (INO) project, which can efficiently detect the atmospheric $ν_μ$ and $\barν_μ$ separately in the multi-GeV energy range. Further, we discuss the advantage of charge identification capability of ICAL and the impact of uncertainties in oscillation parameters while constraining $α_{32}$. We also compare the $α_{32}$ sensitivity of ICAL with that of future long-baseline experiments DUNE and T2HK in isolation and combination.

hep-ph↗

arXiv2024

A plethora of long-range neutrino interactions probed by DUNE and T2HK

Upcoming neutrino experiments will soon search for new neutrino interactions more thoroughly than ever before, boosting the prospects of extending the Standard Model. In anticipation of this, we forecast the capability of two of the leading long-baseline neutrino oscillation experiments, DUNE and T2HK, to look for new flavor-dependent neutrino interactions with electrons, protons, and neutrons that could affect the transitions between different flavors. We interpret their sensitivity in the context of long-range neutrino interactions, mediated by a new neutral boson lighter than $10^{-10}$ eV, and sourced by the vast amount of nearby and distant matter in the Earth, Moon, Sun, Milky Way, and beyond. For the first time, we explore the sensitivity of DUNE and T2HK to a wide variety of $U(1)^\prime$ symmetries, built from combinations of lepton and baryon numbers, each of which induces new interactions that affect oscillations differently. We find ample sensitivity: in all cases, DUNE and T2HK may constrain the existence of the new interaction even if it is supremely feeble, may discover it, and, in some cases, may identify the symmetry responsible for it.

hep-ph↗

arXiv2024

Improved precision on 2-3 oscillation parameters using the synergy between DUNE and T2HK

A high-precision measurement of $Δm^2_{31}$ and $θ_{23}$ is inevitable to estimate the Earth's matter effect in long-baseline experiments which in turn plays an important role in addressing the issue of neutrino mass ordering and to measure the value of CP phase in $3ν$ framework. After reviewing the results from the past and present experiments, and discussing the near-future sensitivities from the IceCube Upgrade and KM3NeT/ORCA, we study the expected improvements in the precision of 2-3 oscillation parameters that the next-generation long-baseline experiments, DUNE and T2HK, can bring either in isolation or combination. We highlight the relevance of the possible complementarities between these two experiments in obtaining the improved sensitivities in determining the deviation from maximal mixing of $θ_{23}$, excluding the wrong-octant solution of $θ_{23}$, and obtaining high precision on 2-3 oscillation parameters, as compared to their individual performances. We observe that for the current best-fit values of the oscillation parameters and assuming normal mass ordering (NMO), DUNE + T2HK can establish the non-maximal $θ_{23}$ and exclude the wrong octant solution of $θ_{23}$ at around 7$σ$ C.L. with their nominal exposures. We find that DUNE + T2HK can improve the current relative 1$σ$ precision on $\sin^{2}θ_{23}~(Δm^{2}_{31})$ by a factor of 7 (5) assuming NMO. Also, we notice that with less than half of their nominal exposures, the combination of DUNE and T2HK can achieve the sensitivities that are expected from these individual experiments using their full exposures. We also portray how the synergy between DUNE and T2HK can provide better constraints on ($\sin^2θ_{23}$ - $δ_{\mathrm{CP}}$) plane as compared to their individual reach.

hep-ph↗

arXiv2024

Probing the interior of Earth using oscillating neutrinos at INO-ICAL

Atmospheric neutrinos offer the possibility of exploring the internal structure of Earth. This information is complementary to the traditional probes of seismic and gravitational studies. While propagating through Earth, the multi-GeV neutrinos encounter the Earth's matter effects due to the coherent forward scattering with the ambient electrons, which alters the neutrino oscillation probabilities. We present how well an atmospheric neutrino oscillation experiment like the 50 kt Iron Calorimeter (ICAL) detector at India-based Neutrino Observatory would validate the presence of Earth's core, measure the location of the core-mantle boundary (CMB), and probe the dark matter (DM) inside the Earth in a unique way through Earth matter effects in neutrino oscillations. Owing to good angular resolution, ICAL can observe the core-passing neutrinos efficiently. Due to its magnetized setup, it would be able to observe neutrinos and antineutrinos separately. With 500 kt$\cdot$yr exposure, the presence of Earth's core can be independently confirmed at ICAL with a median $Δχ^2$ of 7.45 (4.83) for normal (inverted) mass ordering. With 1000 kt$\cdot$yr exposure, ICAL would be able to locate the CMB with a precision of about $\pm$ 250 km at $1σ$. It would also be sensitive to the possible presence of dark matter with 3.5% of the mass of Earth at $1σ$. The charge identification capability of ICAL would play an important role in achieving these precisions.

hep-ph↗

arXiv2023

Present and future constraints on flavor-dependent long-range interactions of high-energy astrophysical neutrinos

The discovery of new, flavor-dependent neutrino interactions would provide compelling evidence of physics beyond the Standard Model. We focus on interactions generated by the anomaly-free, gauged, abelian lepton-number symmetries, specifically $L_e-L_μ$, $L_e-L_τ$, and $L_μ-L_τ$, that introduce a new matter potential sourced by electrons and neutrons, potentially impacting neutrino flavor oscillations. We revisit, revamp, and improve the constraints on these interactions that can be placed via the flavor composition of the diffuse flux of high-energy astrophysical neutrinos, with TeV-PeV energies, i.e., the proportion of $ν_e$, $ν_μ$, and $ν_τ$ in the flux. Because we consider mediators of these new interactions to be ultra-light, lighter than $10^{-10}$ eV, the interaction range is ultra-long, from km to Gpc, allowing vast numbers of electrons and neutrons in celestial bodies and the cosmological matter distribution to contribute to this new potential. We leverage the present-day and future sensitivity of high-energy neutrino telescopes and of oscillation experiments to estimate the constraints that could be placed on the coupling strength of these interactions. We find that, already today, the IceCube neutrino telescope demonstrates potential to constrain flavor-dependent long-range interactions significantly better than existing constraints, motivating further analysis. We also estimate the improvement in the sensitivity due to the next-generation neutrino telescopes such as IceCube-Gen2, Baikal-GVD, KM3NeT, P-ONE, and TAMBO.

hep-ph↗