arXiv subjects

Nityasa Mishra

Publications and source records attributed to Nityasa Mishra.

9 recordsLinked to original sources

arXiv2026

Standard Candles for Supernova Neutrino Detection at DUNE

The Deep Underground Neutrino Experiment (DUNE) far detector is sensitive to $\mathcal{O}(10)$ MeV electron neutrinos through $ν_e$ charged-current reaction with argon. This capability is a unique window into the $ν_e$ component of a Galactic core-collapse supernova flux. Extracting the properties of the supernova spectrum is, however, limited by the poorly-known $ν_e$-Ar cross section. We propose a data-driven strategy that leverages $^8$B solar neutrinos and muon-decay-at-rest neutrinos as standard candles for this process. These calibration samples constrain both the low-energy and high-energy components of the cross section relevant for supernova detection. Our method reduces the reliance on nuclear models, which can bias the extraction of the spectral parameters by as much as 300$\%$.

hep-ph↗

arXiv2026

Sterile Neutrino Mixing Parameters from Solar-Neutrino Coherent Scattering

Recently, dark matter direct-detection experiments have begun their exploration of the ``neutrino fog,'' providing the first hints of detection of solar neutrinos scattering elastically with the nuclei in the detector. In this work, we investigate how such observations can be used to uniquely explore sterile-neutrino parameter space, specifically through mixing with $ν_μ$ and $ν_τ$. While it is challenging to constrain these parameters with current observations -- PandaX, XENONnT, and LZ -- we demonstrate how future measurements (with modest improvements to exposure and systematic uncertainties) can provide useful, complementary information in the search for sterile neutrinos. With an ideal, next-generation direct-detection facility (${\sim}3000$ ton-yr), we can probe parameter space previously unexplored by other methods, including long-baseline and atmospheric searches for this class of new physics.

hep-ph↗

arXiv2026

Directional recoil detection for CEvNS measurements with light nuclei at the Spallation Neutron Source

The coherent elastic scattering of neutrinos on nuclei, also known as CEvNS, has been studied for several years by the COHERENT program of experiments using neutrinos from stopped-pion decays produced at the Spallation Neutron Source (SNS). We propose a new approach for CEvNS measurements at the SNS that aims to complement the COHERENT experiments in two main ways: by reconstructing the angular distribution of CEvNS-induced recoils, and by measuring CEvNS on much lighter target nuclei such as helium, carbon, and fluorine. The proposed detector would employ a gaseous time-projection chamber with a highly segmented charge readout to enable the spatial reconstruction of $\sim$10-500 keV ionisation tracks created by CEvNS-induced recoils. This would enable the simultaneous measurement of the CEvNS recoil energy and scattering angle, thereby allowing event-by-event reconstruction of the neutrino energy. We estimate that a 60:40 He:CF$_4$ gas mixture at atmospheric pressure offers a good trade-off between total target mass and good directionality and could deliver a detection of the angular distribution of CEvNS, even under pessimistic background conditions. We project the sensitivity of 1 and 10 m$^3$-scale detectors in the context of several physics cases, including: the measurement of the Standard Model CEvNS cross section, reconstruction of the flavour-dependent neutrino fluxes, observing the neutrino-induced Migdal effect, constraints on beyond-Standard Model neutrino interactions, and probing 10-eV-scale sterile neutrinos.

hep-ph↗

arXiv2025

Searching for beyond-Standard-Model solar neutrino interactions using directional detectors

Micro-pattern gaseous detectors (MPGDs) are a class of technologies that enable the full three-dimensional spatial reconstruction of ionisation tracks from nuclear and electron recoils in gas. Anticipating near-future 30 m$^3$-scale time projection chambers with MPGD-based readout, we forecast the sensitivity of such directionally-sensitive low-energy recoil detectors to neutrino interactions beyond the Standard Model. We work in the framework of neutrino non-standard interactions (NSIs), and calculate the combined recoil energy-angle distributions of the electron recoil signal generated by solar neutrinos in atmospheric-pressure He:CF$_4$ gas. We estimate the expected exclusion limits that such an experiment could place on various NSI parameters, as well as the mass and coupling of a new light mediator that interacts with electrons and neutrinos. We find that with an achievable background reduction of around a factor of ten from current estimates for a 30 m$^3$ optical-readout detector using this gas mixture, sensitivity to NSI parameters would already approach Borexino's sensitivity. Directionality also allows for event-by-event neutrino energy reconstruction, which would provide a means to resolve some parameter degeneracies present in the modified neutrino cross section in this formalism. Our results strongly motivate the development of small-scale directionally-sensitive gas detectors for neutrino physics.

hep-ph↗

arXiv2025

Scalar non-standard neutrino interactions in Galactic supernovae

We analyze the prospects for studying scalar non-standard interactions (SNSI) using the neutrino burst from a Galactic supernova. SNSI modify the resonant flavor conversion and, correspondingly, the neutronization burst signal, and may be identifiable in future multi-tonne-scale experiments such as DUNE. We show that, in the presence of SNSI, neutrinos propagating out of the dense supernova environment acquire a density-squared-dependent contribution to their mass-squared differences, which in turn modifies the energy levels of the neutrino mass eigenstates. This phenomenon is not present in less dense environments like the Earth or the Sun. For a given mass ordering, supernova neutrinos can improve the sensitivity to SNSI parameters by up to four orders of magnitude compared to that achievable with solar or terrestrial neutrino sources.

hep-ph↗

arXiv2024

$ν_μ$ and $ν_τ$ elastic scattering in Borexino

We perform a detailed study of neutrino-electron elastic scattering using the mono-energetic $^{7}$Be neutrinos in Borexino, with an emphasis on exploring the differences between the contributions of $ν_e$, $ν_μ$, and $ν_τ$. We find that current data are capable of measuring these components such that the contributions from $ν_μ$ and $ν_τ$ cannot be zero, although distinguishing between them is challenging -- the differences stemming from Standard Model radiative corrections are insufficient without significantly more precise measurements. In studying these components, we compare predicted neutrino-electron scattering event rates within the Standard Model (accounting for neutrino oscillations), as well as going beyond the Standard Model in two ways. We allow for non-unitary evolution to modify neutrino oscillations, and find that with a larger exposure (${\sim}30$x), Borexino may provide relevant information for constraining non-unitarity, and that JUNO may be able to accomplish this with its data collection of $^{7}$Be neutrinos. We also consider novel $ν_μ$- and $ν_τ$-electron scattering from a gauged $U(1)_{L_μ- L_τ}$ model, showing consistency with previous analyses of Borexino and this scenario, but also demonstrating the impact of uncertainties on Standard Model mixing parameters on these results.

hep-ph↗

arXiv2023

Solar neutrinos with CE$ν$NS and flavor-dependent radiative corrections

We examine solar neutrinos in dark matter detectors including the effects of flavor-dependent radiative corrections to the CE$ν$NS cross section. Working within a full three-flavor framework, and including matter effects within the Sun and Earth, detectors with thresholds $\lesssim 1$ keV and exposures of $\sim 100$ ton-year could identify contributions to the cross section beyond tree level. The differences between the cross sections for the flavors, combined with the difference in fluxes, would provide a new and unique method to study the muon and tau components of the solar neutrino flux. Flavor-dependent corrections induce a small day-night asymmetry of $< |3 \times10^{-4}|$ in the event rate, which if ultimately accessible would provide a novel probe of flavor oscillations.

hep-ph↗

arXiv2023

There and back again: Solar cycle effects in future measurements of low-energy atmospheric neutrinos

We study the impact of time-dependent solar cycles in the atmospheric neutrino rate at DUNE and Hyper-Kamiokande (HK), focusing in particular on the flux below 1 GeV. Including the effect of neutrino oscillations for the upward-going component that travels through the Earth, we find that across the solar cycle the amplitude of time variation is about $\pm5\%$ at DUNE, and $\pm 1\%$ at HK. At DUNE, the ratio of up/down-going events ranges from 0.45 to 0.85, while at HK, it ranges from 0.75 to 1.5. Over the 11-year solar cycle, we find that the estimated statistical significance for observing time modulation of atmospheric neutrinos is $4.8σ$ for DUNE and $2.0σ$ for HK. Flux measurements at both DUNE and HK will be important for understanding systematics in the low-energy atmospheric flux as well as for understanding the effect of oscillations in low-energy atmospheric neutrinos.

hep-ph↗

arXiv2022

PIP2-BD: GeV Proton Beam Dump at Fermilab's PIP-II Linac

The PIP-II superconducting RF linac is currently under construction at Fermilab and is expected to be completed by the end of 2028. PIP-II is capable of operating in a continuous-wave mode and can concurrently supply 800 MeV protons to a mega-watt, GeV-scale beam dump facility and to LBNF/DUNE. Designs for proton accumulator rings are being studied to bunch the PIP-II protons into the short pulses needed for neutrino and low-mass dark matter experiments. PIP2-BD is a proposed 100-ton LAr scintillation-only experiment, whose detector design is inspired by CENNS-10 and CCM, that would have world-leading sensitivities to BSM physics, including low-mass dark matter produced in the PIP-II proton beam dump.

hep-ex↗