Session J20: Beyond The Standard Model Physics with Neutrinos

Live

The Reactor Antineutrino Anomaly (RAA) is an observed deficit in flux of antineutrinos emitted from nuclear reactors as compared to prediction. One proposal to explain this phenomenon is via the existence of sterile neutrinos: a flavor of neutrino to which other neutrinos can oscillate that does not interact via the weak force. PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, is designed to explore this theory through short-baseline detection of electron antineutrinos emitted from the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. PROSPECT detects neutrinos through inverse beta decay (IBD) reactions on protons, which result in distinctive coincidences between prompt positron events and delayed neutron capture events. Having a neutrino detector on the surface of the earth at a distance 7-11 meters from a nuclear reactor requires careful treatment of various background signals. This presentation will discuss background classes generated by incident cosmogenic fast neutrons with a focus on those that mimic both the prompt and delayed IBD signals and include comparison to simulation results that use reference cosmogenic fluxes. In addition, the time-dependencies of neutron and IBD backgrounds within the detector will be described.   

Live

The Reactor Antineutrino Anomaly is an observed deficit of the measured antineutrino flux compared with theoretical predictions. One possible explanation for this could be the existence of a non-weakly interacting neutrino flavor causing electron antineutrino disappearance via neutrino oscillations at a new, heavier neutrino mass scale. PROSPECT, the Precision Reactor Oscillation Spectrum Experiment, seeks to address the Reactor Antineutrino Anomaly through precise short-baseline measurements of the antineutrino spectrum of uranium-235 at a distance of 7-11 m from the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. As a neutrino detector operated on the surface, PROSPECT requires active background rejection and an accurate measurement of background events during reactor-off periods. One significant background component is through going muons from cosmic ray showers. This talk will address efforts to understand the nature and time dependence of cosmic ray muon backgrounds at HFIR by comparing PROSPECT data with simulation results.   

Live

The Precision Reactor Oscillation and SPECTrum experiment is designed to perform a model-independent search for eV-scale sterile neutrino oscillation and measure electron anti-neutrino spectrum with high precision from the High Flux Isotope Reactor (HFIR) located at ORNL. The anti-neutrino detector, operating on surface level with minimal overburden, uses 4-tons of $^{6}$Li-loaded liquid scintillator optically separated into 14 by 11 segments to detect Inverse Beta Decay(IBD) interactions. Surface detection of reactor anti-neutrinos represents a significant challenge due to the large backgrounds associated with the reactor operation and cosmogenic fast neutrons. Prior background characterization at HFIR site informed the design of passive shielding. Additionally using the outermost active detector layer to veto cosmogenic multi-neutron interactions, PROSPECT observes reactor anti-neutrinos within 2 hours of on-surface data taking at 5$\sigma$ statistical significance with a signal-to-background ratio $>$ 1. In this talk, I will discuss the various sources of backgrounds and the optimized selection process used to identify IBD events.   

Live

In the Standard Model, neutrinos are nearly massless neutral particles that come in three types, called flavors: electron, muon, and tau. In vacuum, the three neutrinos have been found to change from one flavor to another. Nineteen short-baseline nuclear reactor experiments have studied this and provide a result that is known as the "reactor anomaly." Analysis of these experiments with more modern reactor flux indicate that there exists a fourth neutrino. These analyses utilize a magnitude $\chi ^{2}$ function which ignore spectral information. The inclusion of the additional information has been found in the analysis of the ILL experimental to find a significant increase in the evidence for the fourth neutrino, and, rather than a broad region for the phenomenological mixing parameters, specific values of the mass squared differences were found. Here we investigate experiments conducted at the Goesgen Power Plant by the Caltech-SINTUM (CST) collaboration for three separate short baseline reactor experiments. The analysis performed here will first be combined with the analysis of the other sixteen "reactor anomaly experiment," and then included in a global analysis of all relevant experiments.   

Live

The HUNTER experiment (Heavy Unseen Neutrinos from Total Energy-momentum Reconstruction) is a search for sterile neutrinos with masses in the 20-280 keV range. The neutrino missing mass will be reconstructed from 131-Cs electron capture decays occurring in a magneto-optically trapped sample of atoms. Reaction-microscope spectrometers will be used to detect all charged decay products with high solid angle efficiency and LYSO scintillators read out by silicon photomultiplier arrays detect x-rays, each with sufficient resolution to reconstruct the neutrino missing mass. The experiment requires EUHV pressure, very uniform ion extraction electric field and electron confinement magnetic field, large solid angle for x-ray detection, and precision in-situ alignment. Procurement of major components of HUNTER is well underway with some innovative solutions to these requirements.   

Live

The Short Baseline Neutrino (SBN) program comprises three detectors — the Short Baseline Near Detector (SBND), MicroBooNE, and ICARUS — and promises sensitivity to a variety of new physics that has been proposed in order to explain several perplexing short-baseline neutrino anomalies. This talk will describe ongoing developments to assess SBN’s sensitivity to new physics using the SBNfit fitting framework, and also making use of high performance computing. Particular focus will be paid to searches for sterile neutrino oscillations and searches for anomalous single photon production in neutrino interactions at neutrino energies of 0.1-1 GeV.   

Live

Non-standard interactions (NSI) of neutrinos with matter mediated by a scalar field would induce medium-dependent neutrino masses which can modify oscillation probabilities. Generating observable effects requires an ultra-light scalar mediator. We derive a general expression for the scalar NSI using techniques of quantum field theory at finite density and temperature and discuss various limiting cases applicable to the neutrino propagation in different media, such as the Earth, Sun, supernovae and early universe. We also analyze various terrestrial and space-based experimental constraints, as well as astrophysical and cosmological constraints on these NSI parameters, applicable to either Dirac or Majorana neutrinos. By combining all these constraints, we show that observable scalar NSI effects, although precluded in terrestrial experiments, are still possible in future solar and supernovae neutrino data, and in cosmological observations such as cosmic microwave background and big bang nucleosynthesis data.   

The PROSPECT Short-Baseline Reactor Experiment

PROSPECT is a reactor antineutrino experiment whose primary goals are to probe short-baseline oscillations and perform a precise measurement of the U-235 reactor antineutrino spectrum. The PROSPECT detector has collected data at the High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory, with the active volume covering a baseline range of 7-9m. To operate in this environment with tight space constraints, limited overburden and the possibility of reactor-correlated backgrounds, the PROSPECT AD incorporates design features that provide excellent background rejection. These include segmentation and the use of Li-6 doped liquid scintillator with good pulse-shape discrimination properties. In this presentation, we will describe the performance of the PROSPECT detector and the results obtained to date including the detection of reactor antineutrinos with essentially no overburden, the first oscillation exclusion determined by the experiment, and the highest statistics U-235 reactor antineutrino energy spectrum reported to date, The current status and plans for future improvements to the experiment will also be described.   

A Neutrino Disappearance Search for Sterile Neutrinos with the CAPTAIN-Mills Detector at the Los Alamos Neutron Science Center

MiniBooNE (Mini Booster~Neutrino~Experiment) and LSND (Liquid Scintillator Neutrino Detector) have shown compelling evidence for sterile neutrinos at $\Delta m^{\mathrm{2}} \quad \sim $1 eV$^{\mathrm{2}}$ in short baseline neutrino oscillations experiments. In these experiments, a pure muon neutrino beam is used to search for electron neutrino appearance, i.e. $\nu_{\mu } $disappears in$ýý \nu_{e}$, but muon neutrino disappearance searches have shown no anomalies. The CAPTAIN-Mills experiment uses a 10-ton liquid argon scintillation detector to leverage the enhanced cross section from coherent elastic neutrino-nucleus scattering (CE$\nu $NS) to measure muon neutrino disappearance at the Lujan Center at the Los Alamos Neutron Science Center. Lujan is a 100-kW stopped pion source that nominally delivers a 290-ns wide, 800-MeV proton beam onto a tungsten target at 20 Hz, but the beam width can be significantly narrowed to 30 ns. Fast pulsing is critical for isolating the monoenergetic muon neutrino from the other neutrino flavors and neutron backgrounds. Description of the CAPTAIN-Mills detector, the Lujan neutrino source, the expected sensitivities for sterile neutrinos will be presented along with the results obtained from the summer 2018 neutrino test run and a December engineering run.