Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session DB: Mini-Symposium: Neutrinos and Nuclei I: Intro and Recent Double Beta Decay Results |
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Chair: Jason Detwiler, University of Washington Room: Statler |
Tuesday, October 12, 2021 9:30AM - 10:06AM |
DB.00001: Weak Signal, Strong Background -- theoretical developments in the interaction of neutrinos with nuclei Invited Speaker: Steven R Stroberg A number of exciting large-scale international experimental efforts are underway which seek to use neutrinos to learn about extreme astrophysical environments or physics beyond the Standard Model. Such experiments necessarily involve neutrinos interacting with atomic nuclei, which presents a considerable challenge because hadronic and many-body effects constitute a complicated and non-negligible source of background. Effective field theory and ab initio many-body methods provide a promising path to a controlled treatment with quantified uncertainties. I will provide an overview of recent progress in theoretical treatment of neutrino-nucleus interactions, with particular emphasis on matrix elements relevant for neutrinoless double beta decay. |
Tuesday, October 12, 2021 10:06AM - 10:18AM |
DB.00002: Final Results of GERDA on the Search for Neutrinoless Double Beta Decay Ann-Kathrin Schuetz The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating double beta (0νββ) decay of 76Ge, whose discovery would have far-reaching implications in cosmology and particle physics. Using High Purity Germanium (HPGe) detectors enriched in the isotope 76Ge, which were directly immersed into liquid argon (LAr), it exploited the combination of excellent energy resolution of germanium detectors and scintillating properties of LAr. The GERDA experiment achieved an unprecedentedly low background index of 5.2·10-4 counts/(keV·kg·yr) in the signal region and met the design goal to collect 100 kg·yr of exposure in a quasi-background-free regime. In November 2019, after fulfilling and exceeding the design goals of the experiment, data taking was stopped. No signal has been observed, hence a lower limit on the half-life of 0νββ decay in 76Ge has been set at T1/20ν > 1.8·1026 years (90% C.L.) corresponding to an effective Majorana neutrino mass of mββ < 79-180 meV (90% C.L.). The limit coincides with the sensitivity, defined as the median expectation under the no signal hypothesis. |
Tuesday, October 12, 2021 10:18AM - 10:30AM |
DB.00003: Latest Results from the Search of Neutrinoless Double Beta Decay with CUORE Pranava Teja Surukuchi Venkata The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment searching for 0νββ decay that has been able to reach the one-tonne mass scale. The detector, located at the LNGS in Italy, consists of an array of 988 TeO2 crystals arranged in a compact cylindrical structure of 19 towers. CUORE began its first physics data run in 2017 at a base temperature of about 10 mK and in April 2021 released its 3rd result of the search for 0νββ, corresponding to a tonne-year of TeO2 exposure. This is the largest amount of data ever acquired with a solid state detector and the most sensitive measurement of 0vββ decay in 130Te ever conducted. In this talk, we present the current status of CUORE search for 0νββ with the updated statistics of one tonne-yr. |
Tuesday, October 12, 2021 10:30AM - 10:42AM |
DB.00004: Search for Two-Neutrino Double-Beta Decay of 130Te to Excited States of 130Xe with CUORE Daniel Mayer The CUORE experiment is a ton-scale search for neutrinoless double-beta decay (0υββ) composed of an array of 988 tellurium dioxide crystals, each instrumented as a cryogenic macrocalorimeter. While a discovery of 0υββ would herald new physics, the Standard Model process of two-neutrino double-beta decay (2υββ) in 130Te is readily measured by CUORE. However, still unobserved in 130Te are decays wherein the daughter 130Xe nucleus is left in an excited state which subsequently decays via gamma emission, leading to events with energy deposited across multiple crystals. Understanding the branching ratio and spectral shape for such 2υββ decays to excited states can improve nuclear modelling and help constrain the matrix elements involved in searches for neutrinoless double-beta decay. In this talk, I describe progress towards an improved search for 2υββ decays to excited states with an increased exposure of CUORE. This analysis showcases feature selection and event classification tools which exploit CUORE's segmented geometry to increase signal sensitivity. |
Tuesday, October 12, 2021 10:42AM - 10:54AM |
DB.00005: Updated results on the 0νββ decay half-life limit in 100Mo from the full exposure of CUPID-Mo Bradford C Welliver CUPID-Mo was a successful demonstrator experiment for CUPID (CUORE Upgrade with Particle ID), the planned next-generation upgrade of the first ton scale cryogenic calorimetric 0νββ decay experiment, CUORE (Cryogenic Underground Observatory for Rare Events). CUPID-Mo was operated at Laboratoire Souterrain de Modane in France as an array of 20 enriched Li2100MoO4 (LMO) cylindrical scintillating crystals (~200g each) each facing a Ge light detector (LD) and operated at ~20 mK. Both LMOs and LDs were instrumented with NTD thermistors allowing for the collection of both heat and scintillation light. By collecting both heat and light, α events were easily distinguishable from β/γ events, significantly reducing the background resulting from degrated α energy collection in the heat channel. CUPID-Mo demonstrated an energy resolution of ~7 keV (FWHM) at 2615 keV, complete α/(β/γ) discrimination and very low radioactive contamination. Here we report the results of an analysis of the full CUPID-Mo exposure, with details on improved analysis techniques and present an updated limit on the 0νββ decay half-life for 100Mo. A brief overview of other ongoing analyses will also be presented. |
Tuesday, October 12, 2021 10:54AM - 11:06AM |
DB.00006: Update on the Majorana Demonstrator's search for neutrinoless double-beta decay Ian Guinn The Majorana Demonstrator is searching for neutrinoless double-beta decay (0νββ) in 76Ge, a beyond the standard model process that would prove the neutrino is a Majorana fermion if discovered. The experiment has completed operation of a modular array of 44 kg of high purity germanium detectors, in the p-type point contact (PPC), inverted-coaxial point-contact (ICPC), and broad energy germanium (BEGe) geometries. The 30 kg of PPC detectors and 6 kg of ICPC detectors, which belong to the LEGEND experiment, were enriched to 88% in 76Ge. After removing the enriched detectors in March of 2021 for future operation in LEGEND-200, the experiment is continuing to operate 23 BEGe detectors with natural isotopic abundance. To minimize backgrounds, the Demonstrator is constructed from low-background materials and housed inside a compact shield consisting of lead and copper at the Sanford Underground Research Facility (SURF) in Lead, SD. Each of the detector geometries enable the use of pulse shape discrimination techniques that can reject multi-site and surface backgrounds. Furthermore, the experiment has achieved a leading energy resolution of 0.12% FWHM at 2039 keV. This talk will provide an update on recent improvements to the Majorana analysis and future plans for the experiment. |
Tuesday, October 12, 2021 11:06AM - 11:18AM |
DB.00007: The Search for Neutrinoless Double Beta Decay in KamLAND-Zen 800 Aobo Li The discovery of neutrinoless double beta decay (0νββ) would shed light on the persistent puzzle surrounding the origin of neutrino mass and help explain the matter-dominated universe. KamLAND-Zen is one of the leading experiments searching for 0νββ. The first phase of the experiment, called KamLAND-Zen 400, set a world-leading limit on 0νββ lifetime. After the conclusion of KamLAND-Zen 400, a brand new mini-balloon with a larger volume and cleaner surface was instrumented to contain 745 kg of Xe136. Since Jan. 2019, KamLAND-Zen 800 has started data-taking and aims to improve on the previous 0νββ result. A detailed study of the backgrounds in this new data will be presented along with a state-of-the-art approach for classifying backgrounds using a new algorithm, called KamNet. The impact of KamNet on KamLAND-Zen's 0νββ sensitivity will also be presented. |
Tuesday, October 12, 2021 11:18AM - 11:30AM |
DB.00008: Electroweak structure with quantum Monte Carlo methods and local chiral interactions Garrett B King, Saori Pastore, Maria Piarulli Understanding electroweak interactions in light nuclei is crucial for future fundamental physics searches, such as for neutrinoless double $\beta$-decay and long-baseline experiments measuring neutrino oscillation parameters. In order to disentangle new physics signals from nuclear physics effects, an accurate understanding of the underlying nuclear dynamics is necessary. To achieve this, we use quantum Monte Carlo methods to calculate matrix elements of one- and two-body electroweak current operators consistent with the Norfolk interaction, a high-quality local chiral interaction with two- and three-nucleon forces. This combination of approaches for $A \leq 12$ nuclei allows for a systematic analysis of the relative contribution from different current operators to our predictions and provides insight into the model sensitivity of $\beta$-decay matrix elements, muon capture rates, and neutrinoless double $\beta$-decay transition densities and matrix elements. |
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