Session JJ02: V: Neutrino Physics and Astrophysics II

Searching for argon-bound neutron-antineutron oscillation with MicroBooNE using a deep-learning approach.

Massive and deep underground detectors such as the future Deep Underground Neutrino Experiment (DUNE) will offer a great opportunity to search for rare, beyond-Standard Model (BSM) physics signals. One such BSM process is nucleus-bound neutron-antineutron oscillation-a baryon number violating process- followed by antineutron-neutron/proton annihilation that produces a unique, star-like topological signature that should be easily recognizable within a fully active liquid argon time projection chamber (LArTPC) detector. While the future DUNE LArTPC can search for this signature with high sensitivity, existing MicroBooNE data can be used to demonstrate and validate the methodologies that can be used as part of the DUNE search. This talk presents a deep learning-based analysis of MicroBooNE data, making use of a sparse convolutional neural network (CNN) and topological event information to search for argon-bound neutron-antineutron oscillation-like signals in MicroBooNE. This search represents the first-ever search for neutron-antineutron oscillation in a LArTPC.   

The IsoDAR Experiment

The IsoDAR experiment will utilize a novel, compact cyclotron capable of delivering 10 mA of 60 MeV protons in combination with a production target to create a very pure, isotropic antineutrino source, with peak energy around 6 MeV and endpoint around 15 MeV. Paired with a kiloton-scale detector like the planned Liquid Scintillator Counter (LSC) at Yemilab in South Korea, IsoDAR will perform searches for sterile neutrinos, neutrino decay, quantum-mechanical wavepacket effects, non-standard neutrino interactions, new low-mass mediators and axion-like particles---studies that are well-motivated from both a theoretical and experimental standpoint. This talk will focus on the IsoDAR physics program and the current status of the overall project.   

The SBC experiment and calibration plan

The Scintillating Bubble Chamber (SBC) Collaboration is exploring the dark matter and neutrino potential of liquid-noble bubble chambers. These detectors can observe sub-keV nuclear recoils while being blind to electronic recoils. The SBC-Fermilab liquid argon chamber is currently being assembled for commissioning. Once complete we will measure the detector’s response to nuclear and electronic recoils. The nuclear recoil calibration plan combines photo-neutron sources with a precise Thomson scattering calibration down to the 100 eV target threshold. I will show simulated results demonstrating that this calibration strategy can reach the 5% resolution necessary to probe BSM neutrino physics with a reactor CEvNS measurement. A thermal neutron capture calibration could complement the calibration by tagging events with scintillation light from decay gammas. The scintillation response and electronic recoil response will also be measured with gamma sources. With the scalable target volume, low nuclear recoil threshold, and electronic recoil rejection, the liquid noble bubble chamber is perfectly situated to observe reactor neutrino Coherent Elastic neutrino Nuclear Scattering (CEvNS). A future SBC-CEvNS reactor neutrino experiment using liquid argon and has the potential to achieve the highest statistics CEvNS measurement to date as well as the first definitive reactor CEvNS detection.   

Upper Limits on Low-Mass WIMP Annihilation Cross Sections from IceCube Neutrinos

Dark matter is known to be approximately five times more abundant in the universe than baryonic matter. However, its particle nature remains a mystery. One of the leading candidate particles for dark matter are Weakly-Interacting Massive Particles (WIMPs), which are thought to interact only via gravity and the weak force. Some theories suggest that WIMPs could potentially annihilate into Standard Model particles in astrophysical environments. Among a variety of annihilation outcomes is the production of neutrino/antineutrino pairs, either through direct annihilation or indirectly through decay chains, which can be detected by neutrino telescopes like the IceCube Neutrino Observatory at the South Pole. One promising location for dark matter annihilation are dwarf spheroidal galaxies, which have a higher dark matter density and lower astrophysical background relative to a full-sized galaxy. This study presents preliminary results for constraints on the WIMP annihilation cross section for low-mass (≤ 300 GeV) WIMPs in 29 dwarf galaxies using IceCube data from 2011 to 2017.   

Dark Matter Neutrino Scattering from the Galactic Center

Evidence for the existence of dark matter strongly motivates the efforts to study its unknown properties. Additionally, the origin of high-energy astrophysical neutrinos detected by IceCube remains uncertain. If dark matter and neutrinos couple to each other, we can search for a non-zero elastic scattering cross-section. The interaction between an isotropic extragalactic neutrino flux and dark matter would be concentrated in the Galactic Center, where the dark matter column density is largest. The flux of high-energy neutrinos would be attenuated by this scattering and the resulting signal, with correlated energy and arrival direction, can be observed in IceCube. Using the seven years of IceCube data, we perform an unbinned likelihood analysis, searching for several potential DM-neutrino interaction scenarios.   

Exploring new avenues to distinguish Dirac and Majorana neutrinos

Neutrinos are the only known elementary fermions which might be their own antiparticles, i.e. they could be Majorana fermions. When a Majorana neutrino is exchanged in a process, it is possible to have lepton number violation. This has been used to propose various probes for Majorana neutrinos, such as the neutrinoless double beta decay. Additionally, since a Majorana neutrino is quantum mechanically indistinguishable from its antiparticle, quantum statistical considerations could as well be exploited. Since neutrino and antineutrino are never detected close to their point of production, formulating such quantum statistical probes have always been challenging. In this talk we will present a few ideas that exploit quantum statistics to probe the couplings of Majorana neutrinos. These probes are interesting because they are not necessarily constrained by the smallness of neutrino mass. Such probes can potentially probe whether neutrinos participate in any non-standard interactions as well.   

Particle identification for proton and pion event discrimination using the SuperFGD prototype detector simulation

A novel three-dimensional projection scintillator tracker called SuperFGD is one of the key components of the near detector upgrade of the T2K experiment. Due to the ns timing resolution and fine granularity, SuperFGD will provide valuable data for studying neutrino interactions. A prototype of the SuperFGD detector was exposed to a neutron beam in LANL to study the detector response to neutron interactions, critical for future studies of neutrino interactions with a neutron in the final state in the T2K SuperFGD near detector. This talk will present preliminary results in the implementation of particle identification (PID) for proton and pion event discrimination using the SuperFGD prototype detector simulation. This PID development will allow future neutron-induced proton and pion production cross-section measurements on the scintillator using the SuperFGD prototype data.