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 FB: Mini-Symposium: Neutrinos and Nuclei IV: Recent and Future Double Beta Decay Efforts |
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Chair: Andrea Pocar, UMass, Amherst Room: Statler |
Tuesday, October 12, 2021 2:00PM - 2:12PM |
FB.00001: Large-Nc analysis of two-nucleon neutrinoless double beta decay and charge-independence-breaking contact terms Matthias R Schindler, Thomas R Richardson, Roxanne P Springer, Saori Pastore Analyzing the process nn→ppe-e- with the exchange of a light Majorana neutrino, Cirigliano et al. [Phys. Rev. Lett. 120, 202001 (2018)] showed that in chiral effective field theory (ChEFT) a lepton-number-violating contact term is required at leading order in the ChEFT power counting. To estimate the impact of this new contribution, Cirigliano et al. related its size to a combination of isotensor charge-independence-breaking (CIB) nucleon-nucleon interactions by making an assumption about the relative sizes and signs of the isotensor CIB terms. We show that these assumptions can be justified in the limit of the number of color charges Nc becoming large, lending support to the numerical estimates of Cirigliano et al. |
Tuesday, October 12, 2021 2:12PM - 2:24PM |
FB.00002: New Results from NuDot: Double-Beta Decay with Direction Reconstruction in Liquid Scintillator Julieta Gruszko As neutrinoless double-beta decay searches seek to reach into and beyond the inverted hierarchy regime, new strategies are needed to reject background events in kiloton-scale detectors. In monolithic liquid-scintillator-based detectors, otherwise-irreducible backgrounds like 8B solar neutrino scattering could be identified by their event topology using Cherenkov light signals. NuDot is a half-ton prototype that aims to demonstrate this technique with 1 to 2 MeV beta particles, using precision timing to distinguish the Cherenkov and scintillation signals. Following a successful demonstration of the separation technique in the FlatDot test-stand, the NuDot detector was built at Bates Research and Engineering Center. Preliminary results from the commissioning phase of the experiment will be shown. In the coming months, we will continue to conduct surface measurements demonstrating direction reconstruction of calibration source beta events. Following this phase of operation, NuDot will undergo upgrades and continue in an additional surface operation phase at Triangle Universities Nuclear Laboratory, followed by an underground measurement of two-neutrino double-beta decay with direction reconstruction. |
Tuesday, October 12, 2021 2:24PM - 2:36PM |
FB.00003: The SNO+ Experiment Tanner Kaptanoglu The SNO+ experiment is a multipurpose detector with the primary goal of observing neutrinoless double beta decay, but with the opportunity to explore a broad range of physics. SNO+ is currently filled with liquid scintillator and is collecting data. I will discuss the current data, the expected sensitivity to reactor antineutrinos and solar neutrinos during the scintillator phase, the plans to load the scintillator with tellurium, and the future prospects for the neutrinoless double beta decay measurement with SNO+. |
Tuesday, October 12, 2021 2:36PM - 2:48PM |
FB.00004: Double beta decay search with LEGEND-200 Bjoern Lehnert LEGEND (Large Enriched Germanium Experiment for Neutrinoless double beta Decay) uses High Purity Germanium (HPGe) detectors to search for lepton number violation in the neutrino sector. The HPGe detectors are isotopically enriched with 76Ge and immersed in liquid argon (LAr), which serves as shielding and active veto system. |
Tuesday, October 12, 2021 2:48PM - 3:00PM |
FB.00005: LEGEND-1000: A Ton-Scale Search for Neutrinoless Double-Beta Decay in Ge-76 Vincente E Guiseppe Next-generation neutrinoless double-beta decay searches seek the Majorana nature of neutrinos and the existence of a lepton number violating process at a decay half-life corresponding to the inverted-ordering neutrino mass scale, assuming the light Majorana neutrino exchange mechanism. The proposed LEGEND-1000 experiment represents the ton-scale phase of the LEGEND program's search for neutrinoless double-beta decay of 76Ge, which follows upon the current intermediate-stage LEGEND-200 experiment at LNGS in Italy. The LEGEND-1000 design is centered around a 1000-kg mass of p-type, inverted-coaxial, point-contact germanium detectors operated within a liquid argon active shield. This approach has achieved the lowest background levels and the best energy resolution at the decay Q value among the existing technologies as established by the GERDA and MAJORANA DEMONSTRATOR experiments. The LEGEND-1000 experiment's technical design, energy resolution, material selection, and background suppression techniques combine to project a background-free search for neutrinoless double-beta decay in 76Ge at a half-life beyond 1028 yr and a discovery sensitivity that covers the inverted-ordering neutrino mass scale. The innovation behind the LEGEND-1000 design, as well as its technical readiness and discovery potential is presented. |
Tuesday, October 12, 2021 3:00PM - 3:12PM |
FB.00006: Search for Neutrinoless Double Beta Decay with the CUPID Experiment Reina H Maruyama CUPID, the CUORE Upgrade with Particle Identification, is a next-generation tonne-scale bolometric neutrinoless double beta decay experiment. It will probe the Majorana nature of neutrinos and has the potential to observe Lepton Number Violation at the effective neutrino mass scale > 10 meV. CUPID builds on expertise learned from CUORE, and will be installed in the current CUORE infrastructure in the Gran Sasso underground laboratory. The CUPID detector technology, successfully tested in the CUPID-Mo experiment, is based on scintillating bolometers of Li2MoO4 enriched in the isotope of interest Mo-100. In this talk, I will present the science goals and status of the CUPID experiment. |
Tuesday, October 12, 2021 3:12PM - 3:24PM |
FB.00007: An overview of the nEXO experimental design Govinda Adhikari nEXO is a proposed next-generation neutrinoless double-beta decay experiment using a 5-tonne monolithic liquid xenon (LXe) time projection chamber (TPC) to search for the neutrinoless double-beta decay of 136Xe with an estimated half-life sensitivity of ∼ 1028 years at 90% C.L. The nEXO detector inherits various aspects from its predecessor EXO- 200 experiment with an improved detector design to achieve 1% energy resolution at the Q-value and better background discrimination capabilities. The outer detector is a tank with ultra-pure deionized water in which TPC and cryostat are fully submerged and design to shield external backgrounds and exploits as a muon veto detector. In this talk, I will present the design of the outer detector and TPC, charge collection system, photodetectors, and cryogenic readout electronics that are anticipated to improve the current 0νββ decay half-life measurement by two orders of magnitude. |
Tuesday, October 12, 2021 3:24PM - 3:36PM |
FB.00008: Sensitivity and Discovery Potential of the nEXO Experiment Caio Licciardi The nEXO experiment consists of a time projection chamber filled with 5000 kg of isotopically enriched liquid xenon to search for the neutrinoless double beta decay (0νββ) in 136Xe. Progress in the detector design, paired with higher fidelity in its simulation and an advanced data analysis, based on the one used for the final results of EXO-200, produce a sensitivity prediction that exceeds the half-life of 1028 years at the 90% confidence level. The use of custom electroformed copper is now incorporated into the design, leading to a substantial reduction in backgrounds from the intrinsic radioactivity of detector materials. Combining all these developments result in a credible sensitivity estimate that covers the parameter space associated with the inverted neutrino mass ordering, along with a significant portion of the parameter space for the normal ordering scenario, for almost all nuclear matrix elements. In this talk I summarize this work with emphasis on the calculations and results of the nEXO sensitivity to 0νββ exclusion and its discovery potential. |
Tuesday, October 12, 2021 3:36PM - 3:48PM |
FB.00009: Beyond the next generation 0νββ search: An instrument with T1/2 sensitivity of 1030 years Mike Heffner Neutrinoless double beta decay (0νββ) is a promising avenue to search for physics beyond the Standard Model. The observation of 0νββ would show the existence of lepton number violation and the existence of elementary Majorana fermions. Current limits on the half-life are around 1026 years, and next generation experiments will extend the measurement sensitivity to 1028 years. The next generation experiments have substantial discovery potential, but if an observation is not made, the allowed parameter space extends to about 1030 years, assuming neutrinos are Majorana particles and there is no finely tuned cancellation driving the effective Majorana mass to zero. Xenon time projection chambers (TPCs) provide a scalable path to 1030 yr sensitivities, and a plausible research path exists to provide 136Xe in the approximately ktonne quantity required. |
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