Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session D20: Neutrinos II – Neutrinoless Double-Beta Decay: Increasing SensitivitiesFocus Live
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Sponsoring Units: DNP Chair: David Radford, Oak Ridge National Laboratory Room: Washington 5 |
Saturday, April 18, 2020 3:30PM - 4:06PM Live |
D20.00001: The NEXT Experiment Invited Speaker: Benjamin Jones The NEXT collaboration is pursuing a program of high pressure xenon gas experiments with the goal of mounting sensitive, ultra-low background, ton-scale searches for neutrino less double beta decay. This talk will present recent results from the presently running NEXT-White demonstrator, a status update on construction of NEXT-100, and a discussion of the future ton-scale phases. We will also discuss the latest R&D for the NEXT program including studies of diffusion-reducing gas mixtures and the development of barium ion tagging based on single molecule fluorescence imaging. [Preview Abstract] |
Saturday, April 18, 2020 4:06PM - 4:18PM Live |
D20.00002: Recent results from NEW, a demonstrator for the NEXT neutrinoless double beta decay experiment Jonathan Haefner The NEXT (Neutrino Experiment with a Xenon TPC) experiment will search for neutrinoless double beta (0$\nu \beta \beta$) decay from $^{136}$Xe using a high pressure gaseous xenon time projection chamber. The current stage of the experiment, the NEXT-White (NEW) detector, has been acquiring data at Canfranc Underground Laboratory (LSC) in Spain to demonstrate the NEXT capabilities. After reviewing the experiment, as well as the excellent energy resolution and powerful event classification allowed by this technology, we move on to describe recent progress, including resolution studies, demonstration of topological discrimination from calibration data, and thorough understanding of backgrounds. We will also present preliminary results on our 2$\nu \beta \beta$ measurement. [Preview Abstract] |
Saturday, April 18, 2020 4:18PM - 4:30PM Live |
D20.00003: Demonstration of Single Barium Ion Detection in High Pressure Environments for Neutrinoless Double Beta Decay Using On-Off Barium Chemosensors Nicholas Byrnes In the search for neutrinoless double beta decay, the ability to identify and reduce backgrounds is absolutely necessary, given that double beta decay is one nature's slowest decay processes. An advance that would allow us to reject our backgrounds almost entirely would be the ability to efficiently detect the barium daughter of 136-Xe to 136-Ba double beta decay in coincidence with conventional topological and energy cuts to detected electrons, since no conventional radioactive process can produce barium ions or atoms in xenon. The approach under development by the NEXT collaboration involves transporting the barium ion from the active medium onto a glass plane coated with a barium sensitive fluorescent molecule self-assembling monolayer, monitored via fluorescence microscopy. Our previous results have shown that single barium ions can be observed using both commercial and custom designed fluorescent dyes in solution through a technique called Single Molecule Fluorescent Imaging (SMFI). We show here that the new GodXilla pressure microscope system, a novel microscope operating at up to ten bar of xenon gas, can observe single fluorescent barium-chelated molecules at pressure, in the dry phase, using our custom molecules, a crucial step in getting the technique to operate in situ. This talk discusses this major step and the other developments being made for barium tagging in the NEXT collaboration. [Preview Abstract] |
Saturday, April 18, 2020 4:30PM - 4:42PM Live |
D20.00004: Imaging of single Ba atoms and Ba$^{\mathrm{+}}$ ions in solid xenon for barium tagging in next-generation $^{\mathrm{136}}$Xe double beta decay experiments William Fairbank, James Todd, David Fairbank, Alec Iverson, Trey Wager The identification, or ``tagging'' of the barium-136 daughter atom that results from double beta decay of xenon-136 provides a promising technique for elimination of all backgrounds except 2í double beta decay in future generations of $^{\mathrm{136}}$Xe neutrinoless double beta decay experiments. We have demonstrated that individual Barium atoms can be imaged and counted in two of four matrix sites in solid xenon.$^{\mathrm{a}}$ We report new progress towards single Ba$^{\mathrm{+}}$ ion imaging in the one favored matrix site and imaging in the remaining Ba sites. The Ba tagging scheme being developed utilizes a cryogenic probe to trap the $^{\mathrm{136}}$Ba daughter atom in solid xenon and extract it from a liquid xenon time projection chamber, such as the nEXO design concept. The barium atom is then tagged via fluorescence imaging in the solid xenon matrix. When perfected, a count of 1 Ba or Ba$^{\mathrm{+}}$ peak indicates a real double beta decay event; a zero count is evidence of a background event. An important feature of the method is that any residual Ba atoms on the probe surface do not create an observable signal, only those that are captured in the solid xenon. $^{\mathrm{a}}$C. Chambers et al., Nature 569, 203 (2019). [Preview Abstract] |
Saturday, April 18, 2020 4:42PM - 4:54PM Live |
D20.00005: Radioactive Background Modeling for the nEXO Experiment Kyle Leach The sensitivity and discovery potential for $0\nu\beta\beta$-decay are the primary measures to assess the expected performance of the nEXO experiment. These quantities are directly correlated with the “single-site” background event rate around the $0\nu\beta\beta$-decay Q-value, and therefore requires extensive modeling and characterization. As with nearly all deep-underground BSM physics searches, these backgrounds are dominated by trace levels of naturally occurring radioactivity, cosmic-ray material activation, and exposure to alpha-emitting contamination. The nEXO collaboration has performed hundreds of assay measurements and extensive modeling of such backgrounds within the nEXO experiment to address this issue. The progress of which will be discussed in this talk. [Preview Abstract] |
Saturday, April 18, 2020 4:54PM - 5:06PM Live |
D20.00006: Modeling the Effect of Impurities on the Electron Lifetime in Liquid Xenon for nEXO Ako Jamil nEXO is a 5 tonne liquid xenon (LXe) time projection chamber (TPC) planned to search for the neutrinoless double beta decay of $^{136}$Xe with a target half-life sensitivity of about $10^{28}$ years. Electrons from an event within the TPC will be drifted up to 1.3 m and to ensure minimal charge loss nEXO aims to reach an electron lifetime of 10 ms. This lifetime is inversely proportional to the concentration of electro-negative impurities, for which multiple species with different attachment cross-sections may be important. Various sources for impurities such as diffusion out of commonly used plastics, desorption from metal surfaces and leaks to atmosphere were investigated. This talk will go over recent measurements of outgassing from plastics, cross-section measurements of impurities in LXe and the prospects of an empirically driven model for understanding the electron lifetime in LXe for nEXO. [Preview Abstract] |
Saturday, April 18, 2020 5:06PM - 5:18PM Not Participating |
D20.00007: Sensitivity of the nEXO neutrinoless double beta decay experiment Brian Lenardo The nEXO experiment is a proposed next-generation search for the neutrinoless double beta decay (NDBD) of $^{136}$Xe. The primary detector will be a 5-tonne, monolithic liquid xenon TPC enriched to 90\% in the isotope of interest. A detailed study of the expected sensitivity, published in 2016, calculated the 90\% CL exclusion sensitivity on the NDBD half life to be $9.2\times10^{27}$ yrs, approximately two orders of magnitude beyond existing limits. In this talk, we will discuss ongoing work to produce a new evaluation of the sensitivity, given updates to the simulations, analysis, radioassay, and detector design. Specific improvements that have been made since the last publication include detailed modeling of signal development in the charge readout tiles, the development of new machine-learning analyses to improve signal/background separation, detailed accounting for the open field cage design of the nEXO TPC, improved radioassay results of the detector components, and an updated detector geometry which reflects changes made to the engineering design over the past three years. [Preview Abstract] |
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