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 2WD: Workshop on Neutrinoless Double Beta Decay II |
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Chair: Alan Poon, LBNL Room: Kohala 2 |
Tuesday, October 13, 2009 2:00PM - 2:30PM |
2WD.00001: Neutrino Mass Spectrum, Majorana CP-Violation, $\beta\beta$-Decay and Beyond Invited Speaker: The problem of determination of the nature - Dirac or Majorana, of massive neutrinos is discussed. The physics potential of experiments, searching for $\beta\beta-$decay, for providing information on the type of $\nu$-mass spectrum, absolute scale of $\nu$- masses and on the Majorana phases in the PMNS neutrino mixing matrix $U$, is reviewed. The possibility that the CP-violation necessary for the generation of the baryon asymmetry of the Universe is due exclusively to the Majorana CP-violating phase(s) in the PMNS neutrino mixing matrix $U$, is also briefly discussed. [Preview Abstract] |
Tuesday, October 13, 2009 2:30PM - 3:00PM |
2WD.00002: MAJORANA: An Ultra-Low Background Enriched-Germanium Detector Array for Fundamental Physics Measurements Invited Speaker: The {\sc Majorana} collaboration aims to perform a search for neutrinoless double-beta decay (0$\nu\beta\beta$) by fielding arrays of HPGe detectors mounted in ultra-clean electroformed-copper cryostats located deep underground. Recent advances in HPGe detector technology, in particular P-type Point-Contact (PPC) detectors, show great promise for identifying and reducing backgrounds to the 0$\nu\beta\beta$ signal, which should result in improved sensitivity over previous generation experiments. The ultra-low energy threshold possible in PPC detectors also enables a broader physics program including sensitive searches for dark matter and axions. The {\sc Majorana Demonstrator} R\&D program will field three $\sim$20~kg modules of PPC detectors at Sanford Underground Laboratory. Half of the detector mass will be enriched to 86\% in $^{76}$Ge. I will present the motivation, design, recent progress and current status of this R\&D effort, and discuss its physics reach. [Preview Abstract] |
Tuesday, October 13, 2009 3:00PM - 3:30PM |
2WD.00003: NEMO 3 double beta decay experiment and SuperNEMO project Invited Speaker: NEMO 3 is a double beta decay experiment operating in the Laboratoire de Souterraine de Modane (LSM). We will present the latest results of the neutrinoless double beta decays of 7kg of $^{100}$Mo and 1kg of $^{82}$Se, as well as two neutrino double beta decays of various isotopes in the NEMO 3 experiment with the highest precision measurements. The SuperNEMO project is being designed to the next step of the NEMO 3 double beta decay experiment. We will present the current status of the project. [Preview Abstract] |
Tuesday, October 13, 2009 3:30PM - 4:00PM |
2WD.00004: COFFEE BREAK
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Tuesday, October 13, 2009 4:00PM - 4:30PM |
2WD.00005: Status of the DCBA Experiment Invited Speaker: Momentum analyzers called DCBA (Drift Chamber Beta-ray Analyzer) are being developed at KEK in order to study neutrinoless double-beta decay. DCBA consists of drift chambers interleaving thin decay-source plates and a solenoid magnet serving a uniform magnetic field. The momentum of individual beta-ray is measured from the helical track reconstructed in three dimension. Then its kinetic energy is calculable. As for backgrounds, pair creation events are easily rejected by electric charges in the magnetic field. Alpha particles have so large momenta that they don't make helical tracks. Since the vertex point of a double beta-decay event is clearly identified, a single electron track is easily eliminated, and double Compton scatterings are also identified. A prototype called DCBA-T2 had been operated, and the energy resolution of about 150 keV (FWHM) was obtained for 976 keV electrons, which were the internal conversion electrons from Bi-207. The DCBA-T2 has been in engineering run using natural Mo plates of 45 mg/cm2 thickness to check comprehensive capabilities. New prototype DCBA-T3 is now under construction to improve the energy resolution and to increase the source amount accommodated in drift chambers. The main different points from DCBA-T2 are the pitches of signal wires, which are changed from 6 mm to 3 mm, and the strength of magnetic field, which is done from 0.8 kG to 3 kG maximum. In order to improve the energy resolution with the reduction of the multiple scattering of electron in chamber gas, a stronger magnetic field is produced by a super-conducting solenoid. It makes the helical track radius smaller, and then smaller pitches of signal wires are required to obtain enough sampling point data on the helical track. A detector module temporarily named Magnetic Tracking Detector (MTD) has been designed on the basis of DCBA in order to search for Majorana neutrino mass down to 50 meV. Status of DCBA-T2 and T3 will be presented together with the future project of MTD. [Preview Abstract] |
Tuesday, October 13, 2009 4:30PM - 5:00PM |
2WD.00006: The neutrinoless double beta decay experiment COBRA: Status and future plans Invited Speaker: The COBRA experiment uses Cadmium Zinc Telluride (CZT) room-temperature solid-state detectors to search for neutrinoless double beta decays of the isotope $^{116}$Cd as well as for rare decays from several other Cd and Te isotopes. A prototype experiment is currently taking data in the Gran Sasso underground laboratory. In this contribution, recent results from the prototype will be presented. Furthermore, the on-going detector R$\&$D will be described and two detector options for a large-scale experiment made of 420 kg of CZT detectors will be discussed. The first option uses ``calorimetric coplanar grid detector units". Alternatively, finely pixelated detectors may be used with pixel pitches of between 200 and 350 microns. The pixelated detectors would afford the possibility of tracking beta particles inside the detector and distinguishing them from background events. [Preview Abstract] |
Tuesday, October 13, 2009 5:00PM - 5:30PM |
2WD.00007: Status and Progress of GERDA Invited Speaker: The study of neutrinoless double beta decay (DBD) is the most powerful approach to the fundamental question if the neutrino is a Majorana particle, i.e. its own anti-particle. The observation of neutrinoless DBD would not only establish the Majorana nature of the neutrino but also represent a determination of its effective mass if the nuclear matrix element is given. So far, the most sensitive results have been obtained with Ge-76, and the group of Klapdor-Kleingrothaus has made a claim of discovery. Future experiments have to reduce radioactive backgrounds to increase the sensitivity. The GERmanium Detector Array ``GERDA'' [1] is a new double beta-decay experiment which is currently under construction in the INFN Gran Sasso National Laboratory, Italy. It is implementing a new shielding concept by operating bare Ge diodes---enriched in Ge-76---in high purity liquid argon supplemented by a water shield. The aim of ``GERDA'' is to verify or refute the recent claim of discovery, and, in a second phase, to achieve a two orders of magnitude lower background index than recent experiments. The paper will discuss design, physics reach, and status of construction of ``GERDA,'' and present results from various R\&D efforts including long term stability of bare Ge diodes in cryogenic liquids, material screening, cryostat performance, design and production of enriched Ge diodes, cryogenic precision electronics, safety aspects, and Monte Carlo simulations.\\[4pt] [1] http://www.mpi-hd.mpg.de/GERDA/ [Preview Abstract] |
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