Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session 1WJA: Future Prospects of Neutrinoless Double Beta Decay I |
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Chair: Kevin Lesko, Lawrence Berkeley National Laboratory Room: Hilton Kona 5 |
Tuesday, October 23, 2018 9:00AM - 9:30AM |
1WJA.00001: Neutrinoless double beta decay, Leptogenesis, and gauged U(1)μ-τ models. Invited Speaker: Koichi Hamaguchi We will review the Leptogenesis, a mechanism to create the matter-antimatter asymmetry of the Universe, and its implication for the neutrinoless double beta decay. We also discuss extensions of the Standard Model with gauged U(1)μ-τ symmetry, which predicts a large rate of the neutrinoless double beta decay. |
Tuesday, October 23, 2018 9:30AM - 10:00AM |
1WJA.00002: Current Status and Future Prospects of KamLAND-Zen Invited Speaker: Kunio Inoue KamLAND-Zen is searching for neutrino-less double beta decay using Xe-136 dissolved in ultra-low radioactivity liquid scintillator. It has run with 380 kg of 90% enriched Xe-136 and is providing the most stringent upper limit on effective Majorana mass of neutrino, 61-165 meV. Major backgrounds are Bi-214 as a contaminant on the mini-balloon, C-10 from cosmic muon spallation, and energy resolution tail of two neutrino double beta decay. KamLAND-Zen is replacing the mini-balloon with double capacity and specially cleaned mini-balloon so that effective Xe-136 amount can be increased by more than factor 3. Because spallation backgrounds associate preceding muon signal, a sophisticated software selection can drastically reduce C-10 backgrounds. This new phase is called KamLAND-Zen 800 and is expected to start this year with target sensitivity of ~40 meV entering inverted mass hierarchy of neutrinos. It will allow us to verify some theoretical models. In order to cover the inverted hierarchy region, energy resolution must be improved to distinguish neutrino-less and two neutrino double beta decays. KamLAND2-Zen is going to employ high quantum efficiency PMTs with light concentrators, and high light yield liquid scintillator. Energy resolution can be improved by more than factor 2 and the sensitivity will be ~20 meV covering almost entire inverted hierarchy region. Current status of KamLAND-Zen 800 deployment and development of KamLAND2-Zen items will be reported together with future prospects of these projects. |
Tuesday, October 23, 2018 10:00AM - 10:30AM |
1WJA.00003: CANDLES for the study of double beta decay of $^{48}$Ca and its future prospect Invited Speaker: Tadafumi Kishimoto Study of neutrinoless double beta ($0 \nu \beta \beta$) decay becomes of particular importance after the confirmation of neutrino oscillation which shows that neutrinos have mass. They could then be Majorana particles which violate lepton number conservation. Once lepton number non-conservation is verified, we have a scenario to explain how our matter dominated universe is realized. It is known as a leptogenesys scenario. ($0 \nu \beta \beta$) decay is only a known process to verify Majorana nature of neutrino. We have been studying ($0 \nu \beta \beta$) of $^{48}$Ca with the CANDLES detector system. CaF$_2$ crystals are our central detector. The $^{48}$Ca has the highest Q value (4.3 MeV) among double beta decay nuclei. It means that the large decay rate for a given neutrino mass and the least background. We constructed the detector at the Kamioka underground laboratory. We have been running the experiment and obtained the best limit for the lifetime of $^{48}$Ca ($0 \nu \beta \beta$). For the future progress of CANDLES, we are working on enrichment of 48Ca and bolometer system. Small natural abundance of $^{48}$Ca (0.19%) is the shortcoming but indicates potential of 500 times improvement by enrichment paradoxically. Bolometer technique can be applied to CaF$_2$ crystals by which we can expect substantial improvement of energy resolution. I would like to describe the current status of our experiment and its future prospects. |
Tuesday, October 23, 2018 10:30AM - 11:00AM |
1WJA.00004: COFFEE BREAK
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