Future Neutrino Oscillation Experiments Research Articles

Longitudinal kinematic imbalances in neutrino and antineutrino interactions for improved measurements of neutrino energy and the axial vector form factor

Current and future accelerator neutrino oscillation experiments require an improved understanding of nuclear effects in neutrino-nucleus interactions. One important systematic uncertainty is introduced by the collective impact of nuclear effects which bias the reconstruction of the neutrino energy, such as the nuclear removal energy. In this manuscript, we introduce a novel observable for accelerator neutrino oscillation experiments, the visible longitudinal momentum imbalance, reconstructed in charged-current quasielastic interactions from the outgoing charged lepton and nucleon. We demonstrate it to be minimally dependent on the neutrino energy and sensitive to sources of bias in neutrino energy reconstruction. Furthermore, we show how the use of the longitudinal imbalance in antineutrino interactions in a target containing hydrogen allows for an improved, high-purity selection of the interactions on hydrogen. This approach offers the potential for precise measurements of the nuclear axial vector form factor as well as of the antineutrino flux. Published by the American Physical Society 2024

Neutrino Lorentz invariance violation from cosmic fields

From a cosmological perspective, scalar fields are well-motivated dark matter and dark energy candidates. Several possibilities of neutrino couplings with a time-varying cosmic field have been investigated in the literature. In this work, we present a framework in which violations of Lorentz invariance (LIV) and CPT symmetry in the neutrino sector could arise from an interaction among neutrinos with a time-varying scalar field. Furthermore, some cosmological and phenomenological aspects and constraints concerning this type of interaction are discussed. Potential violations of Lorentz and CPT symmetries at present and future neutrino oscillation experiments such as IceCube and KM3NeT can probe this scenario.

Flavor identification of atmospheric neutrinos in JUNO with machine learning

The Jiangmen Underground Neutrino Observatory (JUNO) is designed to determine neutrino mass ordering (NMO) using a large liquid scintillator detector located in southern China. While JUNO's NMO sensitivity mostly comes from reactor neutrinos, atmospheric neutrino oscillations in JUNO can provide complimentary sensitivity via matter effects, and enhance its overall sensitivity in a joint analysis. Neutrino flavor identification is crucial to atmospheric neutrino oscillation measurements, but is traditionally a very difficult task in liquid scintillator detectors such as JUNO. In this paper, we present a novel method for the flavor identification of atmospheric neutrinos in JUNO with machine learning techniques. This method takes features from photomultiplier tube waveforms as inputs, and shows promising results with JUNO simulation. This method could also be applied to other liquid scintillator detectors, potentially benefiting other future atmospheric neutrino oscillation experiments.

Neural network predictions of inclusive electron-nucleus cross sections

We investigate whether a neural network approach can reproduce and predict the electron-nucleus cross sections in the kinematical domain of present and future accelerator-based neutrino oscillation experiments. For this purpose, we consider the large amount of data available to the community via the University of Virginia's Quasielastic Electron Nucleus Scattering Archive and use a residual, fully connected feedforward neural network. We illustrate the training performances of the neural network by comparing its results with experimental data for the electron double-differential cross section on carbon. The agreement between predictions and data is remarkable from quasielastic to deep-inelastic scattering. To test the predicting power of the neural network we consider the numerous kinematical conditions for which experimental cross sections on calcium are available. Furthermore, we show the predictions of the electron-scattering cross sections on oxygen, argon, and titanium: Nuclei of particular interest in the context of present and future accelerator-based neutrino oscillation programs. The agreement between these predictions and the data is comparable to the one of other theoretical models commonly used to calculate electron and neutrino cross sections, such as SuSAv2 and GiBUU. Results obtained with genie, a Monte Carlo event generator, are also discussed for comparison. The good performances obtained with our neural network suggest that neural networks could be exploited for theoretical and experimental investigations of electron- and neutrino-nucleus scattering.

Neutron detection and application with a novel 3D-projection scintillator tracker in the future long-baseline neutrino oscillation experiments

Neutrino oscillation experiments require a precise measurement of the neutrino energy. However, the kinematic detection of the final-state neutron in the neutrino interaction is missing in current neutrino oscillation experiments. The missing neutron kinematic detection results in a feed-down of the detected neutrino energy compared to the true neutrino energy. A novel 3D\textcolor{black}{-}projection scintillator tracker, which consists of roughly ten million active cubes covered with an optical reflector, is capable of measuring the neutron kinetic energy and direction on an event-by-event basis using the time-of-flight technique thanks to the fast timing, fine granularity, and high light yield. The $\bar{\nu}_{\mu}$ interactions tend to produce neutrons in the final state. By inferring the neutron kinetic energy, the $\bar{\nu}_{\mu}$ energy can be reconstructed better, allowing a tighter incoming neutrino flux constraint. This paper shows the detector's ability to reconstruct neutron kinetic energy and the $\bar{\nu}_{\mu}$ flux constraint achieved by selecting the charged-current interactions without mesons or protons in the final state.

Quantifying the second resonance effect in neutrino-Argon interaction using DUNE Near Detector

Heavy nuclear targets are used in neutrino oscillation experiments to boost the statistics of neutrino interactions. The complex nuclear environment contributes to the systematic uncertainty as the inevitable nuclear effects. Inadequate knowledge of the neutrino interaction with the nuclear target along with the imperfect reconstruction of neutrino energy seeds uncertainty in the cross-section. Uncertainty in the cross-section propagates as a systematic uncertainty in the determination of the neutrino oscillation parameters. For precision physics, future neutrino oscillation experiments will require understanding of the neutrino nucleus-interaction and neutrino energy reconstruction with a high level of accuracy. In this work, we aim to quantify the second resonance contributions to the neutrino interaction in Argon for reducing systematic uncertainties in the physics predictions for the DUNE Near Detector (ND). We present the results as the ratio distribution of dσdQ2 for Δ(1232) resonance and the extended analysis to the second resonance region P11(1440), D13(1520), and S11(1535). This inclusion shows a significant contribution to the total cross-section compared to the case where only the Δ(1232) resonance is considered.

Probing free nucleons with (anti)neutrinos

We discuss a method to study free protons and neutrons using ν(ν¯)-hydrogen (H) Charged Current (CC) inelastic interactions, together with various precision tests of the isospin (charge) symmetry using ν and ν¯ CC interactions on both H and nuclear targets. Probing free nucleons with (anti)neutrinos provides information about their partonic structure, as well as a crucial input for the modeling of ν(ν¯)-nucleus (A) interactions. Such measurements concurrently represent a valuable tool to address the main limitations of accelerator-based neutrino scattering experiments on nuclear targets, originating from the combined effect of the unknown (anti)neutrino energy and of the nuclear smearing. To this end, we present a method to impose constraints on nuclear effects and calibrate the (anti)neutrino energy scale in ν(ν¯)-A interactions, which are two outstanding systematic uncertainties affecting present and future long-baseline neutrino oscillation experiments.

Status of Lattice QCD Determination of Nucleon Form Factors and Their Relevance for the Few-GeV Neutrino Program

Calculations of neutrino–nucleus cross sections begin with the neutrino–nucleon interaction, making the latter critically important to flagship neutrino oscillation experiments despite limited measurements with poor statistics. Alternatively, lattice quantum chromodynamics (LQCD) can be used to determine these interactions from the Standard Model with quantifiable theoretical uncertainties. Recent LQCD results of gA are in excellent agreement with data, and results for the (quasi-)elastic nucleon form factors with full uncertainty budgets are expected within a few years. We review the status of the field and LQCD results for the nucleon axial form factor, FA( Q2), a major source of uncertainty in modeling sub-GeV neutrino–nucleon interactions. Results from different LQCD calculations are consistent but collectively disagree with existing models, with potential implications for current and future neutrino oscillation experiments. We describe a road map to solidify confidence in the LQCD results and discuss future calculations of more complicated processes, which are important to few-GeV neutrino oscillation experiments.

Adversarial methods to reduce simulation bias in neutrino interaction event filtering at liquid argon time projection chambers

For current and future neutrino oscillation experiments using large Liquid Argon Time Projection Chambers (LAr-TPCs), a key challenge is identifying neutrino interactions from the pervading cosmic-ray background. Rejection of such background is often possible using traditional cut-based selections, but this typically requires the prior use of computationally expensive reconstruction algorithms. This work demonstrates an alternative approach of using a 3D Submanifold Sparse Convolutional Network trained on low-level information from the scintillation light signal of interactions inside LAr-TPCs. This technique is applied to example simulations from ICARUS, the far detector of the Short Baseline Neutrino (SBN) program at Fermilab. The results of the network, show that cosmic background is reduced by up to 76.3% whilst neutrino interaction selection efficiency remains over 98.9%. We further present a way to mitigate potential biases from imperfect input simulations by applying Domain Adversarial Neural Networks (DANNs), for which modified simulated samples are introduced to imitate real data and a small portion of them are used for adverserial training. A series of mock-data studies are performed and demonstrate the effectiveness of using DANNs to mitigate biases, showing neutrino interaction selection efficiency performances significantly better than that achieved without the adversarial training.

Design and performance of a scintillation tracker for track matching in nuclear-emulsion-based neutrino interaction measurement

Precise measurement of neutrino–nucleus interactions with an accelerator neutrino beam is highly important for current and future neutrino oscillation experiments. To measure muon-neutrino charged-current interactions with nuclear-emulsion-based hybrid detector, muon track matching among the detectors are essential. We describe the design and performance of a newly developed scintillation tracker for the muon track matching in the neutrino–nucleus interaction measurement with nuclear emulsion detectors. The muon tracks are reconstructed using the scintillation tracker and another detector called Baby MIND, then, they are matched with the tracks in nuclear emulsion detectors.The scintillation tracker consists of four layers of horizontally and vertically aligned scintillator bars, covering an area of 1m×1m. In the layer, 24mm-wide plastic scintillator bars are specially arranged with deliberate gaps between each other. By recognizing the hit pattern of the four layers, a precise positional resolution of 2.5mm is achieved while keeping the number of readout channels as small as 256. The efficiency of the track matching is evaluated to be more than 97% for forward-going muons, and the positional and angular resolutions of the scintillation tracker are 2.5mm and 20–40mrad respectively. The results demonstrate the usefulness of the design of the scintillation tracker for the muon track matching in the nuclear-emulsion-based neutrino–nucleus interaction measurements.

Probing scalar dark matter oscillations with neutrino oscillations

If ultra-light dark matter (ULDM) exists and couples to neutrinos, it can be discovered via time-periodic variations in the neutrino mass and mixing parameters. We analyze the current bounds on such a scenario and establish the sensitivity expected for both time-averaged and time-resolved modulations in future neutrino oscillation experiments. We place a special emphasis in our analysis on time modulations of the CP violating mixing phase. We illustrate with a toy model the case where the leading modulation effect can be CP violating while the effect on CP conserving parameters is suppressed. We show a unique imprint that a time-averaged CP violating modulation of ULDM can leave in neutrino oscillations, while direct CP asymmetries vanish.

Model-Independent Test of T Violation in Neutrino Oscillations.

We propose a method to establish time reversal symmetry violation at future neutrino oscillation experiments in a largely model-independent way. We introduce a general parametrization of flavor transition probabilities that holds under weak assumptions and covers a large class of new physics scenarios. This can be used to search for the presence of T-odd components in the transition probabilities by comparing data at different baselines but at the same neutrino energies. We show that this test can be performed already with experiments at three different baselines and might be feasible with experiments under preparation or consideration.

Precision measurements and tau neutrino physics in a future accelerator neutrino experiment

We investigate prospects of building a future accelerator-based neutrino oscillation experiment in China, including site selection, beam optimization and tau neutrino physics aspects. CP violation, non-unitary mixing and non-standard neutrino interactions are discussed. We simulate neutrino beam setups based on muon and beta decay techniques and compare Chinese laboratory sites by their expected sensitivities. A case study on the Super Proton–Proton Collider and the China JinPing Laboratory is also presented. It is shown that the muon-decay-based beam setup can measure the Dirac CP phase by about 14.2° precision at 1σ CL, whereas non-unitarity can be probed down to ∣α ij ∣ ≲ 0.37 (i ≠ j = 1, 2, 3) and non-standard interactions to 0.11 (, μ, τ) at 90% CL, respectively.

Model-independent test of T violation in neutrino oscillations

We propose a method to establish time reversal symmetry violation at future neutrino oscillation experiments in a largely model-independent way. We introduce a general parametrization of flavour transition probabilities which holds under weak assumptions and covers a large class of new-physics scenarios. This can be used to search for the presence of T-odd components in the transition probabilities by comparing data at different baselines but at the same neutrino energies. We show that this test can be performed already with experiments at three different baselines and might be feasible with experiments under preparation/consideration.

Double-hit signature of millicharged particles in 3D segmented neutrino detector

We calculate the production of hypothetical millicharged particles (MCPs) of sub-GeV masses by the J-PARC proton beam in the framework of T2K and future T2HK neutrino oscillation experiments. Concentrating on the region of model parameter space, where an MCP can hit the near neutrino detector twice, we adopt this background-free signature to estimate the sensitivity of T2K and T2HK experiments to MCPs. We find that a previously inaccessible in direct searches region of charges 5×10−4-10−2e for MCP masses 0.1-0.5 GeV can be probed.

Inverse seesaw model with a modular S 4 symmetry: lepton flavor mixing and warm dark matter

In this paper, we present a systematic investigation on simple inverse seesaw models for neutrino masses and flavor mixing based on the modular S 4 symmetry. Two right-handed neutrinos and three extra fermion singlets are introduced to account for light neutrino masses through the inverse seesaw mechanism, and to provide a keV-mass sterile neutrino as the candidate for warm dark matter in our Universe. Considering all possible modular forms with weights no larger than four, we obtain twelve models, among which we find one is in excellent agreement with the observed lepton mass spectra and flavor mixing. Moreover, we explore the allowed range of the sterile neutrino mass and mixing angles, by taking into account the direct search of X-ray line and the Lyman-α observations. The model predictions for neutrino mixing parameters and the dark matter abundance will be readily testable in future neutrino oscillation experiments and cosmological observations.

Physics potential of the combined sensitivity of T2K-II, NOνA extension, and JUNO

Leptonic \textit{CP} violation search, neutrino mass hierarchy determination, and the precision measurement of oscillation parameters for a unitary test of the leptonic mixing matrix are among the major targets of the ongoing and future neutrino oscillation experiments. The work explores the physics reach for these targets by around 2027, when the third generation of the neutrino experiments starts operation, with a combined sensitivity of three experiments: T2K-II, NO$\nu$A extension, and JUNO. It is shown that a joint analysis of these three experiments can conclusively determine the neutrino mass hierarchy. Also, at certain values of \emph{true} \dcp, it provides closely around a $5\sigma$ confidence level (C.L.) to exclude \textit{CP}-conserving values and more than a $50\%$ fractional region of \emph{true} $\delta_{\text{CP}}$ values can be explored with a statistic significance of at least a $3\sigma$ C.L. Besides, the joint analysis can provide unprecedented precision measurements of the atmospheric neutrino oscillation parameters and a great offer to solve the $\theta_{23}$ octant degeneracy in the case of nonmaximal mixing.

Commissioning of a High Pressure Time Projection Chamber with Optical Readout

The measurements of proton–nucleus scattering and high resolution neutrino–nucleus interaction imaging are key in reducing neutrino oscillation systematic uncertainties in future experiments. A High Pressure Time Projection Chamber (HPTPC) prototype has been constructed and operated at the Royal Holloway University of London and CERN as a first step in the development of a HPTPC that is capable of performing these measurements as part of a future long-baseline neutrino oscillation experiment, such as the Deep Underground Neutrino Experiment. In this paper, we describe the design and operation of the prototype HPTPC with an argon based gas mixture. We report on the successful hybrid charge and optical readout using four CCD cameras of signals from 241Am sources.

Studying the neutrino wave-packet effects at medium-baseline reactor neutrino oscillation experiments and the potential benefits of an extra detector

We examine the potential of the future medium-baseline reactor neutrino oscillation (MBRO) experiments in studying neutrino wave-packet impact. In our study, we treat neutrinos as wave packets and use the corresponding neutrino flavor transition probabilities. The delocalization, separation and spreading of the wave packets lead to decoherence and dispersion effects, which modify the plane-wave neutrino oscillation pattern, by amounts that depend on the energy uncertainties in the initial neutrino wave packets. We find that MBRO experiments could be sensitive to the wave-packet impact, since the baseline is long enough and also the capability of observing small corrections to the neutrino oscillations due to excellent detector energy resolution. Besides studying the constraints on the decoherence parameter, we also examine the potential wave-packet impacts on the precision of measuring θ12 and other oscillation parameters in the future medium-baseline reactor neutrino oscillation experiments. Moreover, we also probe the potential benefits of an additional detector for studying such exotic neutrino physics.

Neutrino(antineutrino)–nucleus interactions in the shallow- and deep-inelastic scattering regions

In –nucleon/nucleus interactions shallow inelastic scattering (SIS) is technically defined in terms of the four-momentum transfer to the hadronic system as non-resonant meson production with Q 2 ⪅ 1 GeV2. This non-resonant meson production intermixes with resonant meson production in a regime of similar effective hadronic mass W of the interaction. As Q 2 grows and surpasses this ≈1 GeV2 limit, non-resonant interactions begin to take place with quarks within the nucleon indicating the start of deep inelastic scattering (DIS). To essentially separate this resonant plus non-resonant meson production from DIS quark-fragmented meson production, a cut of 2 GeV in W of the interactions is generally introduced. However, since experimentally mesons from resonance decay cannot be separated from non-resonant produced mesons, SIS for all practical purposes in this review has been defined as inclusive meson production that includes non-resonant plus resonant meson production and the interference between them. Experimentally then for W ⪅ 2 GeV inclusive meson production with W ⪆ (M N + M π ) and all Q 2 is here defined as SIS, while for W ⪆ 2 GeV, the kinematic region with Q 2 ⪆ 1 GeV2 is defined as DIS. The so defined SIS and DIS regions have received varying degrees of attention from the community. While the theoretical/phenomenological study of ν–nucleon and ν–nucleus DIS scattering is advanced, such studies of a large portion of the SIS region, particularly the SIS to DIS transition region, have hardly begun. Experimentally, the SIS and the DIS regions for ν–nucleon scattering have minimal results and only in the experimental study of the ν–nucleus DIS region are there significant results for some nuclei. Since current and future neutrino oscillation experiments have contributions from both higher W SIS and DIS kinematic regions and these regions are in need of both considerable theoretical and experimental study, this review will concentrate on these SIS to DIS transition and DIS kinematic regions surveying our knowledge and the current challenges.