We work on many projects, and the following is just a snapshot, as of January 2020.
Barium Tagging for Neutrinoless Double Beta Decay
One of the fundamental open questions in physics is the nature of the neutrino. Currently the most sensitive approach to determine if the neutrinos are Majorana fermions is the search for Neutrino-less double beta decay. This hypothetical process, if it occurs at all, has a very long half life and would likely be the slowest process ever observed (>10^26 years). Such an observation is extremely difficult, in part due to the amount of detector material required, and the radioactive backgrounds that are intrinsically present in detector materials.
One possible way to reject all backgrounds would be to identify the daughter atom from the decay of xenon, which is barium. This approach is generically called “barium tagging”. At UTA we have partnered with the Foss organic chemistry group to develop a set of custom fluorescent molecules for sensing barium ions. This has been accompanied by a rigorous development of a new type of microscopy where the microscope resides in a Nobel element environment, and RF-based ion concentrators for in-detector sensing of barium. We were the first group in the world to image a single barium diction (image inset), and have now demonstrated a new class of dyes with dry function, working in high pressure environments. If successful this new technique could eliminate the backgrounds in the search for neutrinoless double beta decay.
Searches for Sterile Neutrinos at IceCube
The IceCube Neutrino Telescope is a billion-ton, ice Cherenkov detector at the South Pole. In addition to being a telescope for studying ultra-high energy astrophysical neutrinos, IceCube can also measure the properties of neutrinos produced in the atmosphere of the Earth. The UTA group works in collaboration with our colleagues at MIT to search for signatures of exotic particles called sterile neutrinos. The one-year IceCube search for eV-scale sterile neutrinos was the most sensitive in the world. The results of this search using IceCube’s 8-year dataset containing more than 300,000 neutrino candidates were recently presented for the first time at the TeVPa conference in Australia. We continue to refine this search and extend it to seek evidence of other types of new physics phenomena, exhibited through high energy neutrino oscillations.
Construction of the NEXT-100 Detector
NEXT-100 is the forthcoming iteration of the NEXT program, a sequence of high pressure xenon gas time projection chambers working towards creating a ton-scale, very low background neutrinoless double beta decay search. While most aspects of this technology are easily scalable, some detector elements require R&D in order to be realized on a large scale. NEXT-100 will have the same electronics and sensors as the previous detector, NEXT-White, but all mechanical structures will be scalable to the ton-scale size. This includes high voltage connections reaching 80 kilovolts or more, a scalable field cage, and a large, stable electroluminescence region. UTA designs and tests these components alongside Argonne National Lab before they are assembled and sent for installation at the Laboratorio Subterraneo de Canfranc in Spain.
Searching for New Physics using Atmospheric Neutrinos
The data collected by IceCube Neutrino Observatory in the South Pole can be used to test for many types of hypothetical physical process that would extend our understanding beyond the Standard Model. One possible beyond-standard-model scenario is the existence of new and exotic interactions between neutrinos and matter. These non-standard interactions (NSI’s) would introduce differences in the atmospheric neutrino fluxes measured at IceCube, with a magnitude that depends on the quantity of matter traversed and neutrino energy. If NSI’s are observed, it would be clear a path toward understanding higher energy scale physics beyond the Standard Model.
Another project using IceCube atmospheric neutrino data is a search for decoherence effects in long-baseline neutrino oscillations – a possible signature of quantum gravity. Decoherence is the process of a quantum state converting into a classical one, potentially through interacting with an external environment. In models of quantum gravity invoking spacetime foam, virtual, microscopic black holes fill the universe. The interaction of neutrinos with these virtual black holes would reduce the coherence of oscillations, a signature potentially identifiable by IceCube. We are developing new techniques to search for this effect using IceCube’s high energy muon neutrino sample.
Enhancing Time Projection Chamber Technology
The Time Projection Chamber (TPC), invented by UTA REST group member David Nygren in 1974, is a type of 3D tracking calorimeter that has become pervasive in particle physics. TPCs are used worldwide to test for Majorana neutrinos, search for dark matter, measure neutrino oscillations, study collisions at the LHC, and more. Our group continues to study and hone TPC technology, developing novel gas mixtures with ulta-low diffusion, extending optical detection capabilities, developing new readout methodologies, and creating micro-physical simulations to study and improve performance of gas-phase TPC detectors. We participate in both the DUNE MPD and NEXT programs, as well as collaborating with the UTA neutrino physics group to create enabling new technologies for liquid argon experiments such as the DUNE far detector.
Explorations in Neutrino Phenomenology
We are committed to developing and exploring new ideas in neutrino physics and beyond – from working to understand what the LSND and MiniBooNE neutrino anomalies can tell us about physics beyond the standard model, to studying the production of high energy neutrinos from cosmic ray interactions in the sparse atmosphere of the Sun, to developing models of neutrino oscillations for quantum computers. Creativity and the desire to explore are key elements of the scientific process, and all members of our group are encouraged to follow their ideas where they lead. We believe that every anomaly is an opportunity for discovery, and every new idea is an opportunity to develop understanding.