Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session 1WD: Workshop on Neutrinoless Double Beta Decay I |
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Chair: M. Nomachi, Osaka University Room: Kohala 2 |
Tuesday, October 13, 2009 9:00AM - 9:30AM |
1WD.00001: The Profound Implications of Neutrinoless Double Beta Decay Invited Speaker: The observation of neutrinoless double beta decay, at any nonzero level, would imply that lepton number is not conserved, that neutrinos have Majorana masses, and that neutrinos are their own antiparticles. Majorana neutrino masses are physics far outside the Standard Model. Their existence would be evidence in favor of the see-saw model of the origin of neutrino mass, and evidence in favor of leptogenesis as the explanation of the baryon-antibaryon asymmetry of the universe. This talk will explain the physics of neutrinoless double beta decay, discuss what the observation of this process would teach us, and examine the nature of neutrinos that are their own antiparticles. [Preview Abstract] |
Tuesday, October 13, 2009 9:30AM - 10:00AM |
1WD.00002: CANDLES for the study of $^{48}$Ca double beta decay Invited Speaker: CANDLES is the project to search for double beta decay (DBD) of $^{48}$Ca by using CaF$_2$ scintillators. The $Q$-value of $^{48}$Ca, which is the highest (4.27~MeV) among potential DBD nuclei, is far above energies of $\gamma$-rays from natural radioactivities (maximum 2.615~MeV from $^{208}$Tl decay), therefore we can naturally expect small backgrounds in the energy region we are interested in. We gave the best lower limit on the half-life of neutrino-less double beta decay of $^{48}$Ca by using CaF$_2$(Eu) detector system, ELEGANT VI though further development is highly desirable to reach the mass region of current interest. We have constructed the prototype detector, CANDLES III in our laboratory (Osaka U.) at sea level and studied the basic performance of the system, including the light collection, position reconstruction and background rejection. We are now moving the detector system to new experimental room (room D) at Kamioka underground laboratory (2700~m.w.e.) to avoid large background originated from cosmic rays. At the same time, we are increasing the total mass of the $^{48}$Ca compared to the one in the prototype detector. 96 (instead of 60 in prototype) CaF$_2$ modules which contains 350~g of $^{48}$Ca are immersed in a liquid scintillator (LS) which acts as an active veto (veto phase). The conversion phase contains wavelength shifter (Bis-MSB) which converts the emission light of CaF$_2$(pure) which has a peak in the UV region to the visible one where the quantum efficiency of the PMTs is high enough (maximum at $\sim400$~nm) and materials at the optical path have good transparencies. Scintillation lights from both the CaF$_2$ modules and the liquid scintillator in veto phase are viewed by large PMTs ($48 \times 13$'' and $14 \times 17$'' tubes). All the detector system described above are contained in a water tank which is 3~m in diameter and 4~m in height. The water tank and a purification system of the LS together with LS storage tanks were installed at room D. The purification system of the LS removes the radioactive impurities especially U and Th using the techniques of water-extraction and N$_2$ purge. Other components including the CaF$_2$ modules, the PMTs, the liquid scintillator vessel and DAQ system will be installed soon. [Preview Abstract] |
Tuesday, October 13, 2009 10:00AM - 10:30AM |
1WD.00003: EXO -- An overview Invited Speaker: EXO is a program to develop and operate large neutrino-less double-beta decay experiments and measure Majorana neutrino masses with an ultimate sensitivity below 10 meV. In this talk I will survey the different activities in progress, including the status of the EXO-200 detector that is approaching data taking and the R\&D on Ba tagging and on large detectors in gaseous phase. The talk is given on behalf of the EXO collaboration including scientists from Canada, Russia, Switzerland and the US. [Preview Abstract] |
Tuesday, October 13, 2009 10:30AM - 11:00AM |
1WD.00004: COFFEE BREAK
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Tuesday, October 13, 2009 11:00AM - 11:30AM |
1WD.00005: Neutrinoless Double Beta Decay of 136Xe by KamLAND Invited Speaker: There is, presently, strong evidence from recent neutrino experiments that neutrinos undergo flavor oscillations, and hence must have finite masses. The oscillation results can provide differences between squares of neutrino mass eigenvalues, but cannot determine the absolute mass scale nor its origin. So far only neutrinoless double beta(0$\nu\beta\beta$) decay measurement offers a realistic opportunity to establish the Majorana nature of neutrinos and give the absolute scale of the effective neutrino mass. Global analyses of the oscillation results imply the effective neutrino mass could have a minimum value as large as a few tens of meV for the inverted hierarchy of the neutrino mass spectrum. Next generation 0$\nu\beta\beta$ decay experiments are currently proposed to achieve such mass sensitivity. The KamLAND detector is located in the Kamioka mine, and is filled with 1,000 tons of liquid scintillator. The detector is very sensitive to low energy neutrinos from nuclear reactors and the Earth. We are currently working on reducing backgrounds in the KamLAND to detect very low energy solar neutrinos produced by the $^7$Be reaction in the Sun. We have proposed upgrading the KamLAND detector into a huge 0$\nu\beta\beta$ decay experiment by adding $^136$Xe to the detector volume. Since the sensitivity of the 0$\nu\beta\beta$ experiment is determined by the available source amount and the background rate, the KamLND detector is suitable for this purpose. We mainly present the currect status of the development for upgrading the KamLAND detector toward the 0$\nu\beta\beta$ decay experimnt. [Preview Abstract] |
Tuesday, October 13, 2009 11:30AM - 12:00PM |
1WD.00006: Status of the CUORE Neutrinoless Double-Beta Decay Experiment Invited Speaker: Observation of exotic neutrinoless double-beta decays would indicate that neutrinos are Majorana particles. The rate of the process is sensitive to the effective neutrino mass. Cryogenic Underground Observatory for Rare Events (CUORE), a next-generation large-scale double-beta decay experiment, is currently under construction at the Gran Sasso National Laboratory (LNGS) in Italy. It will be sensitive to the neutrino mass values suggested by recent atmospheric neutrino oscillation experiments in the so-called inverted mass hierarchy. We will review the status of the R\&D and construction efforts and the prospects for the double-beta decay and other measurements with CUORE. [Preview Abstract] |
Tuesday, October 13, 2009 12:00PM - 12:30PM |
1WD.00007: Double Beta Decay in SNO+ Invited Speaker: SNO+ is the follow-up experiment to the Sudbury Neutrino Observatory with liquid scintillator replacing the heavy water. The experiment will detect lower energy solar neutrinos, including the pep and CNO solar neutrinos, and geo and reactor antineutrinos. In addition, SNO+ plans to deploy neodymium in the liquid scintillator to conduct a neutrinoless double beta decay search. Status and plans will be presented. [Preview Abstract] |
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