These proceedings summarize the first MiniBooNE electron antineutrino appearance search results, corresponding to a data sample collected for 3.39$\times10^{20}$ protons on target (POT). The search serves as a direct test of the LSND oscillation signature, and provides complementary information which can be used in studies addressing the MiniBooNE neutrino-mode low-energy excess.
MiniBooNE began running in antineutrino mode on 19 January, 2006. We describe the sensitivity of MiniBooNE to LSND-like nuebar oscillations and outline a program of antineutrino cross-section measurements necessary for the next generation of neutrino oscillation experiments. We describe three independent methods of constraining wrong-sign (neutrino) backgrounds in an antineutrino beam, and their application to the MiniBooNE antineutrino analyses.
We outline a program of antineutrino cross-section measurements necessary for the next generation of neutrino oscillation experiments, that can be performed with one year of data at MiniBooNE. We describe three independent methods of constraining wrong-sign (neutrino) backgrounds in an antineutrino beam, and their application to the MiniBooNE antineutrino cross section measurements.
The single largest background to future numubar to nuebar (numu to nue) oscillation searches is neutral current pi0 production. MiniBooNE, which began taking antineutrino data in January 2006, has the world's largest sample of pi0's produced by antineutrinos in the 1 GeV energy range. These neutral pions are primarily produced through the delta resonance but can also be created through "coherent production." The latter process is the coherent sum of glancing scatters of (anti)neutrinos off a neutron or proton, in which the nucleus is kept intact but a pi0 is created. Current analysis of NC pi0…
The single largest background to future numubar to nuebar (numu to nue) oscillation searches is neutral current pi0 production. MiniBooNE, which began taking antineutrino data in January 2006, has the world's largest sample of pi0's produced by antineutrinos in the 1 GeV energy range. These neutral pions are primarily produced through the delta resonance but can also be created through "coherent production." The latter process is the coherent sum of glancing scatters of (anti)neutrinos off a neutron or proton, in which the nucleus is kept intact but a pi0 is created. Current analysis of NC pi0…
The single largest background to future $\bar{ν_μ}\to \bar{ν_e}$ ($ν_μ\to ν_e$) oscillation searches is neutral current (NC) $π^{0}$ production. MiniBooNE, which began taking antineutrino data in January 2006, has the world's largest sample of reconstructed $π^{0}$'s produced by antineutrinos. These neutral pions are primarily produced through the $Δ$ resonance but can also be created through ``coherent production.'' The latter process is the coherent sum of glancing scatters of antineutrinos off a neutron or proton, in which the nucleus is kept intact but a $π^{0}$ is created. A signature of …
The MiniBooNE Collaboration reports a search for \numu and \numubar disappearance in the \dmsq region of a few \evsq. These measurements are important for constraining models with extra types of neutrinos, extra dimensions an d CPT violation. Fits to the shape of the \numu and \numubar energy spectra reveal no evidence for disappearance at 90% confidence level (CL) in either mode. This is the first test of \numubar disappearance between \dmsq=0.1-10\evsq.
The MiniBooNE experiment has reported a number of high statistics neutrino and anti-neutrino cross sections-among which are the charged current quasi-elastic (CCQE) and neutral current elastic (NCE) neutrino scattering on mineral oil. Recently a study of the neutrino contamination of the anti-neutrino beam has concluded and the analysis of the anti-neutrino CCQE and NCE scattering is ongoing.
The MiniBooNE experiment at Fermilab has updated its search for ν_μ-bar -> ν_e-bar oscillations with data collected through May 2011. This represents a statistics increase of 52% over the result published in 2010. The data favor LSND-like oscillations over a background-only hypothesis at the 91.1% confidence level. While the new result remains equally consistent with LSND, the compatibility with the background-only hypothesis is improved. An excess of 38.6 +- 18.5 ν_e-like events below 475 MeV is observed, consistent with the observation of such an excess in neutrino mode.
MiniBooNE seeks to confirm or refute the LSND muon-antineutrino to electron-antineutrino oscillation signal with high statistical significance and different systematics. MiniBooNE has accumulated the world's largest GeV neutrino data set. MiniBooNE employs a cosmic muon calibration system to study the reconstruction of the energies and directions of muons in the detector. Progress of measurements of the muon neutrino charged-current quasi-elastic and single pion production cross sections are presented.
The analysis of the recent neutral-current elastic neutrino and antineutrino-nucleus scattering cross sections measured by the MiniBooNE Collaboration requires relativistic theoretical descriptions also accounting for the role of final-state interactions. In this work we investigate the sensitivity to final-state interactions and compare the MiniBooNE data with the results obtained in the relativistic Green's function model with different parameterizations for the phenomenological relativistic optical potential.
There is accumulating evidence for a difference between neutrino and antineutrino oscillations at the $\sim 1$ eV$^2$ scale. The MiniBooNE experiment observes an unexplained excess of electron-like events at low energies in neutrino mode, which may be due, for example, to either a neutral current radiative interaction, sterile neutrino decay, or to neutrino oscillations involving sterile neutrinos and which may be related to the LSND signal. No excess of electron-like events ($-0.5 \pm 7.8 \pm 8.7$), however, is observed so far at low energies in antineutrino mode. Furthermore, global 3+1 and …
The single largest background to future $\bar{ν_μ}\to \bar{ν_e}$ ($ν_μ\to ν_e$) oscillation searches is neutral current (NC) $π^0$ production. MiniBooNE, which began taking antineutrino data in January 2006, has the world's largest sample of reconstructed $π^0$'s produced by antineutrinos. These neutral pions are primarily produced through the $Δ$ resonance but can also be created through "coherent production." The latter process is the coherent sum of glancing scatters of antineutrinos off a neutron or proton, in which the nucleus is kept intact but a $π^0$ is created. A signature of this pro…
The MiniBooNE (Booster Neutrino Experiment) experiment is a precise search for neutrino oscillations but is crucially sensitive to background processes that would mimic an oscillation signal. The background sources include intrinsic $ν_{e}$ from kaon and muon decays, mis-identified $π^{0}$, gammas from radiative delta decays, and muon neutrino events mis-identified as electrons. A summary of these backgrounds and the tools to handle them is presented.
The first measurements of antineutrino charged-current quasielastic ($\numub$ CCQE, $\numu + N \to \mup + N'$) and neutral-current elastic ($\numub$ NCE, $\numu + N \to \numu + N$) cross sections with $< E_{\barν} >$ $<$ 1 GeV are presented. To maximize the precision of these measurements, many data-driven background measurements were executed, including a first demonstration of charge separation using a non-magnetized detector. Apart from extending our knowledge of antineutrino interactions by probing a new energy range, these measurements constrain signal and background processes for current…
We discuss the nuclear interactions of neutrinos versus those of antineutrinos, a relevant comparison for CP violation experiments in the neutrino sector. We consider the MiniBooNE quasielastic-like double differential neutrinos and antineutrinos cross sections which are flux dependent and hence specific to the MiniBooNE set-up. We combine them introducing their sum and their difference. We show that the last combination can bring a general information, which can be exploited in other experiments, on the nuclear matrix elements of the axial vector interference term. Our theoretical model repro…
This article reports the status of a $ν_μ \to ν_{e}$ oscillation search in MiniBooNE (Booster Neutrino Experiment) experiment. If an appearance signal is observed, it will imply Physics Beyond the Standard Model such as the existence of light sterile neutrino.
In this short review, we discuss the 2020 MiniBooNE electron neutrino appearance oscillation results with special attention on background predictions relevant to the MiniBooNE oscillation results and other (anti)electron neutrino appearance search experiments.
The physics motivations, design, and status of the Booster Neutrino Experiment at Fermilab, MiniBooNE, are briefly discussed. Particular emphasis is given on the ongoing preparatory work that is needed for the MiniBooNE muon neutrino to electron neutrino oscillation appearance search. This search aims to confirm or refute in a definitive and independent way the evidence for neutrino oscillations reported by the LSND experiment.
The MiniBooNE Collaboration reports initial results from a search for $\barν_μ\to\barν_e$ oscillations. A signal-blind analysis was performed using a data sample corresponding to $3.39 \times 10^{20}$ protons on target. The data are consistent with background prediction across the full range of neutrino energy reconstructed assuming quasielastic scattering, $200 < E_ν^{QE} < 3000$ MeV: 144 electron-like events have been observed in this energy range, compared to an expectation of $139.2 \pm 17.6$ events. No significant excess of events has been observed, both at low energy, 200-475 MeV, and at…
We investigate the MiniBooNE recent data on the antineutrino nucleus interaction, using the same theoretical description with the same parameters as in previous works on neutrino interactions. The double differential quasielastic cross section, which is free from the energy reconstruction problem, is well reproduced by our model once the multinucleon excitations are incorporated. A similar agreement is achieved for the Q^2 distribution.
T2K is a long-baseline neutrino oscillation experiment, in which a muon neutrino beam is produced at J-PARC and detected 295 km away at the Super-Kamiokande detector. The T2K experiment observed electron-neutrino appearance in 2012. This observation enables T2K to explore CP violation in the lepton sector by comparing electron-neutrino appearance and electron-antineutrino appearance. Indeed, the number of observed electron neutrino events up to 2012 is, though within statistical fluctuation, larger than the expectation, which suggests maximal CP violation. Since 2013, T2K has been accumulating…
We propose the addition of scintillator to the existing MiniBooNE detector to allow a test of the neutral-current/charged-current (NC/CC) nature of the MiniBooNE low-energy excess. Scintillator will enable the reconstruction of 2.2 MeV $γ$s from neutron-capture on protons following neutrino interactions. Low-energy CC interactions where the oscillation excess is observed should have associated neutrons with less than a 10% probability. This is in contrast to the NC backgrounds that should have associated neutrons in approximately 50% of events. We will measure these neutron fractions with $ν_μ…
We present an update of our analysis of short-baseline neutrino oscillation data in the framework of 3+1 neutrino mixing taking into account the recent update of MiniBooNE antineutrino data and the recent results of the MINOS search for nu_mu disappearance into sterile neutrinos (the more complicated 3+2 neutrino mixing is not needed since the CP-violating difference between MiniBooNE neutrino and antineutrino data has diminished). The results of our fits of short-baseline neutrino oscillation data including the MiniBooNE low-energy anomaly (now present both in the neutrino and antineutrino da…
We consider the interpretation of the MiniBooNE low-energy anomaly and the Gallium radioactive source experiments anomaly in terms of short-baseline electron neutrino disappearance in the framework of 3+1 four-neutrino mixing schemes. The separate fits of MiniBooNE and Gallium data are highly compatible, with close best-fit values of the effective oscillation parameters Delta m^2 and sin^2 2 theta. The combined fit gives Delta m^2 >~ 0.1 eV^2 and 0.11 < sin^2 2 theta < 0.48 at 2 sigma. We consider also the data of the Bugey and Chooz reactor antineutrino oscillation experiments and the limits …
We construct a neutrino model of three twin neutrinos in light of the neutrino appearance excesses at LSND and MiniBooNE. The model, which includes a twin parity, naturally predicts identical lepton Yukawa structures in the Standard Model and the twin sectors. As a result, a universal mixing angle controls all three twin neutrino couplings to the Standard Model charged leptons. This mixing angle is predicted to be the ratio of the electroweak scale over the composite scale of the Higgs boson and has the right order of magnitude to fit the data. The heavy twin neutrinos decay within the experim…
This thesis describes an analysis developed for the MicroBooNE experiment to investigate an anomalous excess of electron-like events observed in the MiniBooNE detector. The hypothesis investigated here is that the MiniBooNE anomaly represents appearance of electron neutrinos. Using an amalgam of novel Deep Learning and standard algorithmic techniques this analysis reconstructs and identifies a highly pure sample of charged current quasi-elastic muon neutrino and electron neutrino interactions. This thesis describes the steps in the analysis chain and provides data-to-simulation comparisons for…
The MiniBooNE and SciBooNE collaborations report the results of a joint search for short baseline disappearance of \bar{ν_μ} at Fermilab's Booster Neutrino Beamline. The MiniBooNE Cherenkov detector and the SciBooNE tracking detector observe antineutrinos from the same beam, therefore the combined analysis of their datasets serves to partially constrain some of the flux and cross section uncertainties. Uncertainties in the ν_μ background were constrained by neutrino flux and cross section measurements performed in both detectors. A likelihood ratio method was used to set a 90% confidence level…
The MiniBooNE experiment at Fermilab reports results from an analysis of $\bar ν_e$ appearance data from $11.27 \times 10^{20}$ protons on target in antineutrino mode, an increase of approximately a factor of two over the previously reported results. An event excess of $78.4 \pm 28.5$ events ($2.8 σ$) is observed in the energy range $200<E_ν^{QE}<1250$ MeV. If interpreted in a two-neutrino oscillation model, $\barν_μ\rightarrow\barν_e$, the best oscillation fit to the excess has a probability of 66% while the background-only fit has a $χ^2$-probability of 0.5% relative to the best fit. The dat…
We consider possible indications of Very-Short-BaseLine (VSBL) electron neutrino disappearance into sterile neutrinos in MiniBooNE neutrino data and Gallium radioactive source experiments. We discuss the compatibility of such a disappearance with reactor and MiniBooNE antineutrino data. We find a tension between neutrino and antineutrino data which could be due to: 1) statistical fluctuations; 2) underestimate of systematic uncertainties; 3) exclusion of our hypothesis of VSBL nu_e disappearance; 4) a violation of CPT symmetry. Considering the first possibility, we present the results of a com…
The MiniBooNE Collaboration reports first results of a search for $ν_e$ appearance in a $ν_μ$ beam. With two largely independent analyses, we observe no significant excess of events above background for reconstructed neutrino energies above 475 MeV. The data are consistent with no oscillations within a two neutrino appearance-only oscillation model.
The IsoDAR antineutrino source, which produces a flux from 8Li isotope decay at rest, when paired with the proposed JUNO (Jiangmen Underground Neutrino Observatory) detector, has unprecedented sensitivity to anti-nu_e disappearance for oscillations at high Delta m^2. Assuming CPT invariance, the sensitive region for anti-nu_e disappearance can be used to restrict the allowed parameter space of an anti-nu_mu to anti-nu_e appearance signal. The 5 sigma sensitivity of this experiment covers the entire anti-nu_mu to anti-nu_e allowed parameter space from a combined fit to short-baseline experiment…
We show that the rate of charged-current muon-neutrino events with a hard internal bremsstrahlung photon is consistent with the excess electron-neutrino candidate events reported by the MiniBoone and LSND (decay in flight) experiments. Hard photons radiated by the muon leg in charged-current neutrino interactions (neutrino-Nucleon->muon+gamma+nucleon) are a significant source of background that should be considered by current and future muon-neutrino to electron-neutrino neutrino oscillations appearance experiments (e.g. LSND, MiniBoone, SuperK, MINOS, T2K and NOVA).
The MiniBooNE experiment at Fermilab reports results from a search for $\bar ν_μ\rightarrow \bar ν_e$ oscillations, using a data sample corresponding to $5.66 \times 10^{20}$ protons on target. An excess of $20.9 \pm 14.0$ events is observed in the energy range $475<E_ν^{QE}<1250$ MeV, which, when constrained by the observed $\bar ν_μ$ events, has a probability for consistency with the background-only hypothesis of 0.5\%. On the other hand, fitting for $\barν_μ\rightarrow\barν_e$ oscillations, the best-fit point has a $χ^2$-probability of 8.7\%. The data are consistent with $\bar ν_μ\rightarro…
A recently developed Standard-Model Extension (SME) formalism for neutrino oscillations that includes Lorentz and CPT violation is used to analyze the sidereal time variation of the neutrino event excess measured by the Liquid Scintillator Neutrino Detector (LSND) experiment. The LSND experiment, performed at Los Alamos National Laboratory, observed an excess, consistent with neutrino oscillations, of ${\barν}_e$ in a beam of ${\barν}_μ$. It is determined that the LSND oscillation signal is consistent with no sidereal variation. However, there are several combinations of SME coefficients that …
Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the PMNS mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free p…
The KARMEN experiment at the spallation neutron source ISIS used \numub from \mup--decay at rest in the search for neutrino oscillations \numubnueb in the appearance mode, with p(\nueb,e+)n as detection reaction of \nueb. In total, 15 candidates fulfill all conditions for the \nueb signature, in agreement with the background expectation of 15.8+-0.5 events, yielding no indication for oscillations. A single event based likelihood analysis leads to upper limits on the oscillation parameters: sin^2(2theta)<1.7x10e-3 for Dm^2>100 eV^2 and Dm^2<0.055 eV^2 for sin^2(2theta)=1 at 90% confidence. Thus…
As limits improve on the neutrino mixing angles and mass-squared differences, the focus of T2K has shifted towards studying antineutrino oscillation. This will give an insight into CP violation (if P($\barν_μ \rightarrow \barν_{e}) \neq \mbox{P}(ν_μ \rightarrow ν_e)$) and CPT violation (if P($\barν_μ \rightarrow \barν_μ) \neq \mbox{P}(ν_μ \rightarrow ν_μ)$) in the lepton sector. This poster summarises the most recent T2K antineutrino oscillation results, from data collected using a $\barν_μ$-enhanced neutrino beam corresponding to $4.01 \times 10^{20}$ protons on target (roughly $1/3$ of the t…
We report on $ν_e$ and $\barν_e$ appearance in $ν_μ$ and $\barν_μ$ beams using the full MINOS data sample. The comparison of these $ν_e$ and $\barν_e$ appearance data at a 735 km baseline with $θ_{13}$ measurements by reactor experiments probes $δ$, the $θ_{23}$ octant degeneracy, and the mass hierarchy. This analysis is the first use of this technique and includes the first accelerator long-baseline search for $\barν_μ\rightarrow\barν_e$. Our data disfavor 31% (5%) of the three-parameter space defined by $δ$, the octant of the $θ_{23}$, and the mass hierarchy at the 68% (90%) C.L. We measure …
We explore the hypothesis that the unexplained data from LSND and MiniBooNE are evidence for a new, heavy neutrino mass-eigenstate that mixes with the muon-type neutrino and decays into an electron-type neutrino and a new, very light scalar particle. We consider two different decay scenarios, one with Majorana neutrinos, one with Dirac neutrinos; both fit the data equally well. We find a reasonable, albeit not excellent, fit to the data of MiniBooNE and LSND. The decaying-sterile-neutrino hypothesis, however, cleanly evades constraints from disappearance searches and precision measurements of …
MiniBooNE reports the first absolute cross sections for neutral current single π^0 production on CH_2 induced by neutrino and antineutrino interactions measured from the largest sets of NC π^0 events collected to date. The principal result consists of differential cross sections measured as functions of π^0 momentum and π^0 angle averaged over the neutrino flux at MiniBooNE. We find total cross sections of (4.76+/-0.05_{stat}+/-0.76_{sys})*10^{-40} cm^2/nucleon at a mean energy of <E_ν>=808 MeV and (1.48+/-0.05_{stat}+/-0.23_{sys})*10^{-40} cm^2/nucleon at a mean energy of <E_ν>=664 MeV for ν_…
There exists a need to address and resolve the growing evidence for short-baseline neutrino oscillations and the possible existence of sterile neutrinos. Such non-standard particles require a mass of $\sim 1$ eV/c$^2$, far above the mass scale associated with active neutrinos, and were first invoked to explain the LSND $\bar ν_μ\rightarrow \bar ν_e$ appearance signal. More recently, the MiniBooNE experiment has reported a $2.8 σ$ excess of events in antineutrino mode consistent with neutrino oscillations and with the LSND antineutrino appearance signal. MiniBooNE also observed a $3.4 σ$ excess…
This letter presents the results from the MiniBooNE experiment within a full "3+1" scenario where one sterile neutrino is introduced to the three-active-neutrino picture. In addition to electron-neutrino appearance at short-baselines, this scenario also allows for disappearance of the muon-neutrino and electron-neutrino fluxes in the Booster Neutrino Beam, which is shared by the MicroBooNE experiment. We present the 3+1 fit to the MiniBooNE electron-(anti)neutrino and muon-(anti)neutrino data alone, and in combination with MicroBooNE electron-neutrino data. The best-fit parameters of the combi…
The present paper highlights the data analysis status of the OPERA experiment. The experiment was designed to perform the neutrino interactions analysis on event-by-event basis, and optimized to search for $ν_μ \rightarrow ν_τ$ oscillation in appearance mode, also allowing to perform a $ν_{e}$ appearance search. We review the data simulation and the analysis chains implemented to search for $ν_τ$ interactions. The main kinematical parameters sensitive to the neutrino flavor are discussed, the uncertainties of the event parameter estimation are reviewed, and the main sources of background for t…
Standard three-flavor neutrino oscillations have well explained by a wide range of neutrino experiments. However, the anomalous results, such as electron-antineutrino excess seen by LSND and MiniBooNE do not fit the three-flavor paradigm. This can be explained by an additional fourth flavor sterile neutrino at a larger scale than the existing three flavor neutrinos. The NOvA experiment consists of two finely segmented, liquid scintillator detectors operating 14 .6 mrad off-axis from the NuMI muon-neutrino beam. The Near Detector is located on the Fermilab campus, 1 km from the NuMI target, whi…
The two long-baseline experiments T2K and NO$ν$A have recently presented new findings. T2K has shown the first $\bar ν_e$ appearance data while NO$ν$A has released the first $ν_e$ appearance results. These data are of particular importance because they allow us to probe for the first time in a direct (or manifest) way the leptonic CP-violation. In fact, it is the first time that a hint of CP-violation arises from the comparison of the observations of neutrinos and antineutrinos. We consider the implications of such new results both for the standard 3-flavor framework and for the non-standard 3…
