Search For Neutrino Oscillations Research Articles

Decoherence effects in reactor and Gallium neutrino oscillation experiments: a QFT approach

We adopt the quantum field theoretical method to calculate the amplitude and event rate for a neutrino oscillation experiment, considering neutrino production, propagation and detection as a single process. This method allows to take into account decoherence effects in the transition amplitude induced by the quantum mechanical uncertainties of all particles involved in the process. We extend the method to include coherence loss due to interactions with the environment, similar to collisional line broadening. In addition to generic decoherence induced at the amplitude level, the formalism allows to include, in a straightforward way, additional damping effects related to phase-space integrals over momenta of unobserved particles as well as other classical averaging effects. We apply this method to neutrino oscillation searches at reactor and Gallium experiments and confirm that quantum decoherence is many orders of magnitudes smaller than classical averaging effects and therefore unobservable. The method used here can be applied with minimal modifications also to other types of oscillation experiments, e.g., accelerator based beam experiments.

Neutrino Oscillation Results and Search for Neutrino Sterile States

Neutrino Oscillation Results and Search for Neutrino Sterile States

First Constraints on Light Sterile Neutrino Oscillations from Combined Appearance and Disappearance Searches with the MicroBooNE Detector.

We present a search for eV-scale sterile neutrino oscillations in the MicroBooNE liquid argon detector, simultaneously considering all possible appearance and disappearance effects within the 3+1 active-to-sterile neutrino oscillation framework. We analyze the neutrino candidate events for the recent measurements of charged-current ν_{e} and ν_{μ} interactions in the MicroBooNE detector, using data corresponding to an exposure of 6.37×10^{20} protons on target from the Fermilab booster neutrino beam. We observe no evidence of light sterile neutrino oscillations and derive exclusion contours at the 95% confidence level in the plane of the mass-squared splitting Δm_{41}^{2} and the sterile neutrino mixing angles θ_{μe} and θ_{ee}, excluding part of the parameter space allowed by experimental anomalies. Cancellation of ν_{e} appearance and ν_{e} disappearance effects due to the full 3+1 treatment of the analysis leads to a degeneracy when determining the oscillation parameters, which is discussed in this Letter and will be addressed by future analyses.

Liquid Argon Time Projection Chamber Trigger Development with MicroBooNE

The Micro Booster Neutrino Experiment (MicroBooNE) is a Liquid Argon Time Projection Chamber (LArTPC) neutrino detector at Fermilab that has been operating since 2015. It aims to perform v-Ar cross-section measurements, explore the low-energy excess reported by the MiniBooNE experiment and perform a combined search for sterile neutrino oscillations as part of three LArTPCs that make up the Short Baseline Neutrino (SBN) Program at Fermilab. Since MicroBooNE is currently in an R&D phase, it offers a unique opportunity for the implementation and testing of TPC-based triggers as R&D towards the Deep Underground Neutrino Experiment (DUNE). One of the technical challenges of DUNE that we aim to address with this study is that of efficient self-triggering of a LArTPC utilizing TPC signal information. This capability will enable searches for rare processes in DUNE, such as neutrino interactions from a potential galactic supernova burst. This talk will describe the MicroBooNE TPC readout system and ongoing R&D efforts to develop and demonstrate TPC-based triggering.

Search for sterile neutrino oscillations using RENO and NEOS data

We present a reactor model independent search for sterile neutrino oscillation using 2\,509\,days of RENO near detector data and 180 days of NEOS data. The reactor related systematic uncertainties are significantly suppressed as both detectors are located at the same reactor complex of Hanbit Nuclear Power Plant. The search is performed by electron antineutrino\,($\overline{\nu}_e$) disappearance between six reactors and two detectors with baselines of 294\,m\,(RENO) and 24\,m\,(NEOS). A spectral comparison of the NEOS prompt-energy spectrum with a no-oscillation prediction from the RENO measurement can explore reactor $\overline{\nu}_e$ oscillations to sterile neutrino. Based on the comparison, we obtain a 95\% C.L. excluded region of $0.1<|\Delta m_{41}^2|<7$\,eV$^2$. We also obtain a 68\% C.L. allowed region with the best fit of $|\Delta m_{41}^2|=2.41\,\pm\,0.03\,$\,eV$^2$ and $\sin^2 2\theta_{14}$=0.08$\,\pm\,$0.03 with a p-value of 8.2\%. Comparisons of obtained reactor antineutrino spectra at reactor sources are made among RENO, NEOS, and Daya Bay to find a possible spectral variation.

Beyond the Classroom: Profiling Muon Flux in Relation to Overburden in Fermilab’s MINOS Tunnel

With support from QuarkNet, high school students investigated the effect of overburden on muon flux by collecting data from Fermilab’s Main Injector Neutrino Oscillation Search (MINOS) tunnel. Muon flux varied due to a change in overburden created by a 103-meter deep access shaft. A profile of muon flux as a function of distance from the access shaft was measured by observing muon flux from different locations within the tunnel.

Effective Neutrino Masses from Four Flavor Neutrino Mixing Matrix

We consider the four neutrino oscillation that accommodate the all neutrino oscillation data. We consider the range of the corresponding mixing parameters by the result of neutrino oscillation experiments. Implicaion of the neutrino oscillation search for the neutrino mass square difference and mixing are discussed. We determine the possible values of the effective majorana neutrino mass |<m>|=|{sum }_{j}U_{ej}^{2}m_{j}| in the four neutrino scenario. In the four-neutrino scheme there is an upper bound on | < m > | of the normal mass order is 2.0074eV for α = 0∘,β = 0∘andγ = 0∘. In the case of inverted mass order the upper bound on | < m > | is 2.0069eV for α = 0∘,β = 0∘andγ = 0∘.

Improved short-baseline neutrino oscillation search and energy spectrum measurement with the PROSPECT experiment at HFIR

We present a detailed report on sterile neutrino oscillation and U-235 antineutrino energy spectrum measurement results from the PROSPECT experiment at the highly enriched High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. In 96 calendar days of data taken at an average baseline distance of 7.9 m from the center of the 85 MW HFIR core, the PROSPECT detector has observed more than 50,000 interactions of antineutrinos produced in beta decays of U-235 fission products. New limits on the oscillation of antineutrinos to light sterile neutrinos have been set by comparing the detected energy spectra of ten reactor-detector baselines between 6.7 and 9.2 meters. Measured differences in energy spectra between baselines show no statistically significant indication of antineutrinos to sterile neutrino oscillation and disfavor the Reactor Antineutrino Anomaly best-fit point at the 2.5$\sigma$ confidence level. The reported U-235 antineutrino energy spectrum measurement shows excellent agreement with energy spectrum models generated via conversion of the measured U-235 beta spectrum, with a $\chi^2$/DOF of 31/31. PROSPECT is able to disfavor at 2.4$\sigma$ confidence level the hypothesis that U-235 antineutrinos are solely responsible for spectrum discrepancies between model and data obtained at commercial reactor cores. A data-model deviation in PROSPECT similar to that observed by commercial core experiments is preferred with respect to no observed deviation, at a 2.2$\sigma$ confidence level.

Vertex-finding and reconstruction of contained two-track neutrino events in the MicroBooNE detector

We describe algorithms developed to isolate and accurately reconstruct two-track events that are contained within the MicroBooNE detector. This method is optimized to reconstruct two tracks of lengths longer than 5cm. This code has applications to searches for neutrino oscillations and measurements of cross sections using quasi-elastic-like charged current events. The algorithms we discuss will be applicable to all detectors running in Fermilab's Short Baseline Neutrino program (SBN), and to any future liquid argon time projection chamber (LArTPC) experiment with beam energies ∼ 1 GeV. The algorithms are publicly available on a GITHUB repository [1]. This reconstruction offers a complementary and independent alternative to the Pandora reconstruction package currently in use in LArTPC experiments, and provides similar reconstruction performance for two-track events.

Statistical interpretation of sterile neutrino oscillation searches at reactors

A considerable experimental effort is currently under way to test the persistent hints for oscillations due to an eV-scale sterile neutrino in the data of various reactor neutrino experiments. The assessment of the statistical significance of these hints is usually based on Wilks’ theorem, whereby the assumption is made that the log-likelihood is chi ^2-distributed. However, it is well known that the preconditions for the validity of Wilks’ theorem are not fulfilled for neutrino oscillation experiments. In this work we derive a simple asymptotic form of the actual distribution of the log-likelihood based on reinterpreting the problem as fitting white Gaussian noise. From this formalism we show that, even in the absence of a sterile neutrino, the expectation value for the maximum likelihood estimate of the mixing angle remains non-zero with attendant large values of the log-likelihood. Our analytical results are then confirmed by numerical simulations of a toy reactor experiment. Finally, we apply this framework to the data of the Neutrino-4 experiment and show that the null hypothesis of no-oscillation is rejected at the 2.6 sigma level, compared to 3.2 sigma obtained under the assumption that Wilks’ theorem applies.

Constraints on light singlet fermion interactions from coherent elastic neutrino-nucleus scattering

The exotic singlet fermions $\ensuremath{\chi}$, with a mass ${m}_{\ensuremath{\chi}}\ensuremath{\lesssim}50\text{ }\text{ }\mathrm{MeV}$, could be produced at the coherent elastic neutrino-nucleus scattering ($\mathrm{CE}\ensuremath{\nu}\mathrm{NS}$) experiments through the $\ensuremath{\nu}\mathcal{N}\ensuremath{\rightarrow}\ensuremath{\chi}\mathcal{N}$ process. Due to the coherent enhancement, it offers a unique way to study how $\ensuremath{\chi}$ interacts with the Standard Model (SM) sector. Based on the most general dimension-6 effective Lagrangian, we perform a comprehensive study on the relevant interaction between $\ensuremath{\chi}$ and the SM sector. From the current and future COHERENT and future CONUS experiments, we obtain the upper bounds on the Wilson coefficients for the dipole, scalar, vector, and tensor interactions. For ${m}_{\ensuremath{\chi}}$ below 10 MeV, future CONUS data has the best sensitivity, while for ${m}_{\ensuremath{\chi}}$ between 10 MeV--50 MeV, the current and future COHERENT bounds dominate. These limits are complementary to those from neutrino oscillation and collider searches. Moreover, the bounds do not depend on the charge conjugation property of $\ensuremath{\chi}$, nor whether $\ensuremath{\chi}$ is dark matter or not.

Probing Beyond Standard Model Physics via Oscillations with IceCube DeepCore

For many years IceCube DeepCore has measured atmospheric neutrino interactions in the optically clear, deep ice at the South Pole. Analysing only three years of data has yielded the most precise measurements of the atmospheric neutrino oscillation parameters above 5 GeV. Measuring oscillations at these high energies, well above the tau-production threshold, and over extremely long baselines, provides strong constraints on new, Beyond Standard Model physics in a region of phase space uniquely accessed with atmospheric neutrinos. Here we report on the most recent searches for non-standard atmospheric neutrino oscillations with IceCube DeepCore.

The AQUA-RICH project

The AQUA-RICH project, a long baseline and atmospheric neutrino experiment proposed by Tom Ypsilantis during the last decade of the last century, is briefly reviewed. The detector proposal is discussed within the context of the searches for neutrino oscillations at that time and as part of the longstanding seminal ideas and key contributions provided by Tom Ypsilantis in the development of the RICH technique.

Cosmic muons measurements in the DANSS experiment

DANSS is a highly segmented detector, which contains 2500 one meter long plastic scintillator strips. The DANSS detector is placed under an industrial reactor of the Kalininskaya Nuclear Power Plant. The distance to the core is varied on-line from 10.7 to 12.7 m, and the primary task of the experiment is a search for short-distance neutrino oscillations. This work contains results of the cosmic muons study based on the data obtained with the DANSS detector. In order to achieve these results, the specific algorithm of muon track reconstruction with 97 % efficiency was developed. We also present some preliminary results on the annual variability in the flux of cosmic muons, an evaluation of the < Ethrcosθ > parameter and the correlation coefficient.

Modeling of a MeV-scale particle detector based on organic liquid scintillator

The detectors based on the liquid scintillator (LS) monitored by an array of photo-multiplier tubes (PMT) are often used in low energy experiments such as neutrino oscillation studies and search for dark matter. Detectors of this kind operate in an energy range spanning from hundreds of keV to a few GeV providing a few percent resolution at energies above 1 MeV and allowing to observe fine spectral features. This article gives a brief overview of relevant physical processes and introduces a new universal simulation tool LSMC (Liquid Scintillator Monte Carlo) for simulation of LS-based detectors equipped with PMT arrays. This tool is based on the Geant4 framework and provides supplementing functionality for ease of configuration and comprehensive output. The usage of LSMC is illustrated by modeling and optimization of a compact detector prototype currently being built at Baksan Neutrino Observatory.

PROSPECT- A Precision Reactor Oscillation and Spectrum Experiment

PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, is an effort to resolve anomalous results observed in previous neutrino physics experiments. The primary physics goals of PROSPECT are to perform a search for short baseline neutrino oscillations (Δm2 ∼ 1eV2) and to make a high precision measurement of the 235U reactor antineutrino energy spectrum. PROSPECT will operate close to the Oak Ridge National Laboratory’s High Flux Isotope Reactor, where very little cosmic-ray attenuating overburden is available. To make precision measurements in this difficult environment, PROSPECT has developed a segmented detector design using a 6Li-doped liquid scintillator which provides excellent energy resolution and background rejection.

First Search for Short-Baseline Neutrino Oscillations at HFIR with PROSPECT.

This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of ^{235}U at the High Flux Isotope Reactor. PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, consists of a segmented 4ton ^{6}Li-doped liquid scintillator detector covering a baseline range of 7-9m from the reactor and operating under less than 1m water equivalent overburden. Data collected during 33 live days of reactor operation at a nominal power of 85MW yield a detection of 25 461±283 (stat) inverse beta decays. Observation of reactor antineutrinos can be achieved in PROSPECT at 5σ statistical significance within 2h of on-surface reactor-on data taking. A reactor model independent analysis of the inverse beta decay prompt energy spectrum as a function of baseline constrains significant portions of the previously allowed sterile neutrino oscillation parameter space at 95%confidence level and disfavors the best fit of the reactor antineutrino anomaly at 2.2σ confidence level.

Neutrino Physics at Kalinin Nuclear Power Plant: 2002 – 2017

The results of the research in the field of neutrino physics obtained at Kalinin nuclear power plant during 15 years are presented. The investigations were performed in two directions. The first one includes GEMMA I and GEMMA II experiments for the search of the neutrino magnetic moment, where the best result in the world on the value of the upper limit of this quantity was obtained. The second direction is tied with the measurements by a solid scintillator detector DANSS designed for remote on-line diagnostics of nuclear reactor parameters and search for short range neutrino oscillations. DANSS is now installed at the Kalinin Nuclear Power Plant under the 4-th unit on a movable platform. Measurements of the antineutrino flux demonstrated that the detector is capable to reflect the reactor thermal power with an accuracy of about 1.5% in one day. Investigations of the neutrino flux and their energy spectrum at different distances allowed to study a large fraction of a sterile neutrino parameter space indicated by recent experiments and perform the reanalysis of the reactor neutrino fluxes. Status of the short range oscillation experiment is presented together with some preliminary results based on about 170 days of active data taking during the first year of operation.

Physics Program of the Short-Baseline Near Detector

SBND (Short-Baseline Near Detector) will be a 112 ton liquid argon TPC neutrino detector located 110 m from the target of the Fermilab Booster Neutrino Beam. SBND, together with the MicroBooNE and ICARUS-T600 detectors at 470 m and 600 m, respectively, make up the Fermilab Short-Baseline Neutrino (SBN) Program. SBN will search for new physics in the neutrino sector by testing the sterile neutrino hypothesis in the 1 eV2 mass squared region with unrivaled sensitivity. SBND will measure the unoscillated beam flavor composition to enable precision searches for neutrino oscillations via both electron neutrino appearance and muon neutrino disappearance in the far detectors. With a data sample of millions of neutrino interactions (both electron and muon neutrinos), SBND will also perform detailed studies of the physics of neutrino-argon interactions, even in rare channels. In this poster the physics program of SBND will be presented.

SBND: Status of the Fermilab Short-Baseline Near Detector

SBND (Short-Baseline Near Detector) will be a 112 ton liquid argon TPC neutrino detector located 110m from the target of the Fermilab Booster Neutrino Beam. SBND, together with the MicroBooNE and ICARUS-T600 detectors at 470m and 600m, respectively, make up the Fermilab Short-Baseline Neutrino (SBN) Program. SBN will search for new physics in the neutrino sector by testing the sterile neutrino hypothesis in the 1 eV2 mass-squared region with unrivaled sensitivity. SBND will measure the un-oscillated beam flavor composition to enable precision searches for neutrino oscillations via both electron neutrino appearance and muon neutrino disappearance in the far detectors. With a data sample of millions of neutrino interactions (both electron and muon neutrinos), SBND will also perform detailed studies of the physics of neutrino-argon interactions, even in rare channels. In addition, SBND plays an important role in an on-going R&D effort within neutrino physics to develop the LArTPC technology toward many-kiloton-scale detectors for next generation long-baseline neutrino oscillation experiments. The design details and current status of the detector is presented here.