Session B04: Neutrinoless Double-Beta Decay: Physics Results and Perspectives

Live

nEXO is a proposed next generation neutrinoless double beta decay experiment with a design sensitivity for the half-life of $^{136}$Xe neutrinoless double beta decay of $\sim10^{28}$~yr. The single-phase isotopically enriched liquid xenon time projection chamber design is based on the success of the EXO-200 experiment, which completed its physics run in 2018 with a total exposure of $234.1$~kg~yr. EXO-200 demonstrated ultra-low background construction techniques, good energy resolution, and excellent background discrimination based on multi-parameter measurements of events, enhanced through machine learning techniques. EXO-200 achieved a sensitivity of $5.0\times10^{25}$~yr and a limit on the half-life of $^{136}$Xe neutrinoless double beta decay of $3.5\times10^{25}$~yr at 90\% confidence level. Scaling up from the 200~kg EXO-200 to the 5~tonne nEXO detector will significantly increase the source mass as well as improve background discrimination through the monolithic detector design.   

Live

Understanding the nature of the neutrino mass is one of the most elusive--and one of the most important--questions in the current quest for beyond-standard-model physics. Experiments that can establish a Majorana component of the neutrino mass will provide key insights into physical processes with the potential to explain a number of phenomena, including the origin of the observed matter-antimatter asymmetry in the universe. The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale crystal calorimeter at Laboratori Nazionali del Gran Sasso designed to search for lepton-number-symmetry violation through the observation of neutrinoless double-beta decay in Te-130. Now in its third year of operation, CUORE has accumulated a total exposure of over 650 kg-yr of physics-sensitive data. New results from CUORE establish a lower limit of 3.2e25 yr (90\% C.I.) for the half-life of neutrinoless double-beta decay in Te-130, using the first 372.5 kg-yr of analyzed exposure. In addition to implementing significant improvements to the operational and analysis procedures, the most recent results from CUORE set the stage for the future CUORE Upgrade with Particle IDentification (CUPID), which incorporates light detectors for enhanced particle discrimination and background reduction. In this talk, we discuss the most recent results from the CUORE experiment, and provide an overview of the upcoming plans and current status of CUPID.   

Live

The LEGEND experiment aims for unprecedented sensitivity for the discovery of neutrinoless double-beta decay using a large array of HPGe detectors enriched in the isotope $^{76}$Ge. The experimental approach marries the ultra-low background materials and techniques as well as the high-resolution electronics developed for the MAJORANA experiment with the active liquid-argon veto technology pioneered in the GERDA experiment, along with new developments in HPGe detector technologies. A first 200-kg phase, LEGEND-200, is already under construction at LNGS and expects to begin commissioning in 2021. A ton-scale phase, LEGEND-1000, with sensitivity to half-lives exceeding 10$^{28}$ years, is competing for major US funding. This talk will overview the MAJORANA and LEGEND experiments. New results from MAJORANA on double-beta decay as well as background understanding and other physics will be presented, along with the status and near-term plans of the experiment. I will also discuss progress toward the construction of LEGEND-200, planning for the ton-scale phase, and the future prospects of the LEGEND experimental program.