Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session C12: Minisymposium: Low Energy Neutrinos I: Neutrinoless Double-Beta Decay I |
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Chair: Vincente Guiseppe, Oak Ridge National Lab Room: Hilton Waikoloa Village Kona 5 |
Tuesday, November 28, 2023 7:00PM - 7:30PM |
C12.00001: Neutrinoless Double-Beta Decay: To the Ton Scale and Beyond Invited Speaker: Julieta Gruszko Why is the universe dominated by matter, and not antimatter? Neutrinos, with their changing flavors and tiny masses, could provide an answer. If the neutrino is a Majorana particle, meaning that it is its own antiparticle, it would reveal the origin of the neutrino's mass, demonstrate that lepton number is not a conserved symmetry of nature, and provide a path to leptogenesis in the early universe. To discover whether this is the case, we must search for neutrinoless double-beta decay, a theorized process that would occur in some nuclei. By searching for this extremely rare decay, we can explore new physics at energy scales that only existed in the seconds following the Big Bang. |
Tuesday, November 28, 2023 7:30PM - 7:45PM |
C12.00002: Recent Progress in the MAJORANA DEMONSTRATOR Background Model Ethan Blalock The MAJORANA DEMONSTRATOR was a neutrinoless double-beta decay experiment that operated 44 kg of Ge detectors, of which 30 kg were enriched in the candidate isotope 76Ge. The DEMONSTRATOR concluded in March 2021 and set a 0νββ half-life limit of T1/2 > 8.3×1025 yrs based on its full exposure. The DEMONSTRATOR also achieved one of the lowest background rates in the region of the 2039 keV Q-value, 15.7 cnts/(FWHM t y). However, this background rate is significantly higher than the rate of 2.9 cnts/(FWHM t y) projected by material assays and simulations. An excess of 232Th decay chain events has been observed. Background model fits aim to understand this deviation from assay-based projections, potentially determine the source location(s) of observed backgrounds, and allow a precision measurement of the two-neutrino double-beta decay half-life. Fits confirm the origin of the 232Th excess is not from near-detector components, which informed design decisions for the next-generation LEGEND experiment. Recent findings from background model fits and material assays have suggested some potential sources of the 232Th excess. Studies of systematic uncertainties are ongoing, and will help complete a background model. |
Tuesday, November 28, 2023 7:45PM - 8:00PM |
C12.00003: Denoising Algorithms for the CUORE Experiment Kenneth Vetter The Cryogenic Underground Observatory for Rare Events (CUORE) experiment is an ongoing search for neutrinoless double beta decay located at the Gran Sasso National Laboratory (LNGS) in Italy. Recent work using seismometric and geological data has demonstrated that the CUORE detector is sensitive to vibrational noise from sea storms near LNGS in the Tyrrhenian and Adriatic seas. We have also shown that the quality of CUORE data can be improved with noise decorrelation algorithms using data from auxiliary devices including microphones, accelerometers, and seismometers. We have also motivated an expanded non-linear model which improves the performance of the algorithm for the CUORE detector. Here I will discuss the implementation of these noise decorrelation algorithms in the CUORE analysis framework and their implementation in the latest analysis of CUORE data. The results of the noise decorrelation including the impact on the energy resolution across the CUORE detector for many years of data-taking will also be discussed. |
Tuesday, November 28, 2023 8:00PM - 8:15PM |
C12.00004: Studying Track-Like Events with CUORE Daniel Mayer Located underground within the Laboratori Nazionali del Gran Sasso, CUORE is the first tonne-scale operating cryogenic neutrinoless double-beta decay experiment. While modest in volume compared to traditional tracking detectors, its size and segmented geometry are sufficient for reconstructing through-going high-energy particles, such as cosmic ray muons which survive the journey underground. Analyses are underway to leverage CUORE as a segmented detector for particle tracking, aided by algorithms using multi-objective optimization to reconstruct such events with high fidelity. Currently, the application of these efforts is two-pronged: firstly, to enable the in situ study of cosmic ray muons in CUORE, and to characterize any remaining cosmogenically-induced backgrounds while underground. Secondly, to exploit CUORE's low-background environment to search for exotic track-like phenomena, such as Beyond-the-Standard Model fractionally-charged particles which would exhibit suppressed energy depositions across the detector. This presentation will provide an overview of the track-like program in CUORE. |
Tuesday, November 28, 2023 8:15PM - 8:30PM |
C12.00005: A search for solar axions with CUORE and other low-energy analyses Samantha Pagan The Cryogenic Underground Observatory for Rare Events (CUORE) has a broad physics program ranging from its primary search for neutrinoless double-beta (0νββ) to direct dark matter searches. As an array of 988 TeO2 bolometers at Gran Sasso National Laboratory, CUORE is a low background experiment with an energy resolution of ∼ 7.8 keV FWHM at 2527.5 keV, the Q-value of 0νββ in 130Te. CUORE has collected over 2 tonne-years of TeO2 exposure. Developments in analysis techniques increase CUORE’s sensitivity to multiple rare-event searches in the low-energy region of ~5 to 100 keV, including WIMP and solar axion searches in TeO2. These techniques include low-energy cuts, efficiency calculations, and denoising data. This talk will overview CUORE’s low-energy searches and analysis tools. The analysis for solar Axion Like Particles (ALPs) will be discussed in detail. |
Tuesday, November 28, 2023 8:30PM - 8:45PM |
C12.00006: Acquiring First Data with LEGEND-200 Brady Bos
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Tuesday, November 28, 2023 8:45PM - 9:00PM |
C12.00007: First Background Results from LEGEND-200 Erin Engelhardt The Large Enriched Germanium Experiment for Neutrinoless double-beta Decay (LEGEND) is designed to search for neutrinoless double-beta decay (0νββ) in the 76Ge isotope. The first phase, LEGEND-200, aims for a discovery sensitivity at a half life of 1027 years and requires a reduction of backgrounds by a factor of 2.5 with respect to previous experiments. The performance of LEGEND-200 is critical for the design and development of the subsequent phase, LEGEND-1000. LEGEND-200 has currently been operating with 101 detectors (142 kg) installed into the array, with low-background data-taking having started in early 2023. In this talk we will cover the performance of background rejection techniques and will present results from the first months of LEGEND-200 data-taking. |
Tuesday, November 28, 2023 9:00PM - 9:15PM |
C12.00008: Searching for Beyond-Standard-Model Physics with LEGEND-1000 Samuel L Watkins LEGEND-1000 is a next-generation experiment to search for neutrinoless double-beta decay of the Ge-76 isotope. This ton-scale experiment uses enriched high-purity Ge detectors surrounded by a large active liquid Ar shield, deployed deep underground. Because of the low noise and low energy thresholds of these detectors, along with the low background design of LEGEND-1000, this experiment provides an excellent opportunity for searches for new physics beyond neutrinoless double-beta decay. These include searches for dark matter candidates, exotic nuclear decays, tests of fundamental symmetries, emissions of additional particles during two-neutrino double-beta decays, and more. This talk will briefly describe the LEGEND-1000 program, continuing with a focus on the strategies and expected sensitivities of the experiment for these searches for physics beyond the standard model. |
Tuesday, November 28, 2023 9:15PM - 9:30PM |
C12.00009: The search of neutrinoless double beta decay with the NEXT experiment Carmen Romo Luque The NEXT experiment is trying to find the extremely rare neutrinoless double beta decay of 136Xe using the technology of high pressure xenon gas time projection chambers with electroluminescent amplification. The detection of this process would imply that the neutrino is a Majorana particle and the total lepton number would not be conserved, which could be related to the cosmological asymmetry between matter and antimatter through leptogenesis. After the successful operation of the NEXT-White detector, which demonstrated the excellent energy resolution of 1% at Qββ, validated the reconstruction algorithms and the background model, made a measurement of the two-neutrino double beta decay of 136Xe and performed a demonstration of the 0νββ search capabilities of the NEXT technology, the current phase holding around 100 kg of Xe is being constructed at the Laboratorio Subterráneo de Canfranc (Spain). NEXT-100 is expected to enhance the NEXT energy resolution and run with lower background and better event containment to reach a sensitivity of about 6 × 1025 yr after a run of 3 effective years. It will also assess the background model and will serve as a preparation for the tonne-scale. In this talk, the results obtained with the NEXT-White detector, the NEXT-100 construction status and the prospects of future NEXT detectors will be reported.
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Tuesday, November 28, 2023 9:30PM - 9:45PM |
C12.00010: An overview of the nEXO experiment Zepeng Li nEXO is a next-generation liquid xenon experiment to search for neutrino-less double beta decay (0νββ) of 136Xe using a monolithic 5-tonne liquid xenon time projection chamber. Ionization electrons and scintillation photons from energy deposits in liquid xenon will be recorded with a segmented anode and a large SiPM array. nEXO is designed to achieve 1% energy resolution at the 0νββ Q-value and be built with low radioactivity materials. This talk will present recent progress in the detector design and R&D, an improved modeling of signal readout, and a deep-learning-based event discrimination and data analysis architecture. These improvements result in an estimated discovery potential for 0νββ at 0.74×1028 years at 3σ significance in 10 years of data taking. |
Tuesday, November 28, 2023 9:45PM - 10:00PM |
C12.00011: A Novel HPGe Characterization Apparatus in the Search for Neutrinoless Double-Beta Decay David A Hervas Aguilar A novel HPGe Compton scanner was constructed at the Max Planck Institute for Physics in Munich. In this apparatus, gamma rays deposit energy in the Ge lattice, inducing a signal coincident with that of a position-and-energy sensitive camera. Position reconstruction in large-volume Ge detectors with a millimeter level resolution and practical detector scanning times was demonstrated. The scanning apparatus was employed to characterize the bulk of a 2 kg Inverted Coaxial Point-Contact detector. It was hypothesized that in such large volume detectors, deep hole trapping in the bulk could lead to the severe energy degradation of signals. At 95 K, no evidence of significant deep hole trapping was found. This is of importance for the next generation of germanium-based neutrinoless double-beta decay experiments, where at the ton-scale even small underperforming volumes could populate the signal window with energy degraded signals. Using the same apparatus, the first experimental images of the depletion surface of a large-volume, non-segmented germanium detector were produced. It was shown that a modified impurity model of the detector, which incorporates the evolution of the depletion surface at different biases, outperforms the conventional model of the impurity profile. Pulse-shape simulation is heavily reliant on such models. Thus, a precise understanding of impurities is critical to the development of background rejection techniques for germanium-based rare event searches. |
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