Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session H12: Neutrinoless Double-Beta Decay and Neutrino Mass |
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Sponsoring Units: DNP DPF Chair: Andrew Hime, Los Alamos National Laboratory Room: Marriott Tampa Waterside Room 11 |
Sunday, April 17, 2005 8:30AM - 8:42AM |
H12.00001: The \textit{Majorana }Neutrinoless Double-Beta Decay Experiment Reyco Henning The proposed \textit{Majorana} experiment is an enriched, segmented, HPGe detector array that will search for the neutrinoless double-beta decay of $^{76}$Ge and dark matter. The construction will proceed in a staged approach, the first being an assembly of on the order of 200-kg of enriched germanium crystals, with the option to increase to $\sim $1 ton. Majorana will employ pulse-shape discrimination, detector segmentation, careful materials selection, and active and passive shielding to suppress backgrounds. An overview of the Majorana experiment will be presented in this talk and more detailed discussions will follow in subsequent talks. [Preview Abstract] |
Sunday, April 17, 2005 8:42AM - 8:54AM |
H12.00002: Analysis of Backgrounds in the Majorana Experiment Dong-Ming Mei The search for neutrinoless double-beta decay requires experiments with extremely low levels of background from other sources. Double-beta decay experiments require a well founded and considered background understanding to guide the detector design and development. Today the Majorana collaboration has explored elimination or mitigation techniques for several types of background known form the previous generation of experiments. Because ultimately the backgrounds determine the sensitivity of any double-beta decay experiment, it is important to predict and understand the origin and the components of as yet undetected backgrounds to plan for appropriate reduction or mitigation methods. We summarize the known and expected backgrounds for Majorana, with particular emphasis on the muon-induced background in the detector fabrication, transportation on the surface and the detector operation underground. These background estimates guide the pre-commissioning efforts on the all aspects of the Majorana detector development including the shield and the depth requirements. [Preview Abstract] |
Sunday, April 17, 2005 8:54AM - 9:06AM |
H12.00003: Calibrating Arrays of Germanium Detectors for Double-Beta Decay Victor Gehman The Majorana Project will endeavor to provide direct limits on the effective Majorana mass of the electron neutrino through the measurement of neutrinoless double-beta decay in $^{76}$Ge. Our goal is an experiment sensitive to the effective neutrino mass at the level of a few hundred meV with the option of scaling up to a sensitivity of approximately 50 meV. The experiment will consist of several modules, each a close-packed array of many (tens to hundreds) of germanium detectors in a single cryostat enriched to 86\% in $^{76}$Ge. A major technological challenge in constructing such a large array of detectors is calibrating them all in a systematic, reproducible manner (particularly those on the inside of the array). We present a report on several possible calibration schemes as well as current efforts to implement and test them at Los Alamos National Laboratory using a ``Clover'' detector (a close-packed array of four 800g, two-fold segmented natural germanium detectors). [Preview Abstract] |
Sunday, April 17, 2005 9:06AM - 9:18AM |
H12.00004: Using a germanium detector array to mimic double-beta decays to excited states Kareem Kazkaz In the wake of neutrino oscillation experiments verifying that neutrinos have mass, there has been a lot of interest in $^{76}$Ge double-beta decay. Double-beta decays can proceed either to the ground state or an excited state of the daughter nucleus. The ratios of the rates of these decay modes can give guidance to determining the underlying structure of nuclear matrix elements. The rates of these decays, however, are very small, so for the purpose of developing analysis toolkits for the Majorana Experiment it helps to create similar signals with rates useable in a non-low-background environment. We present methods of using a segmented natural germanium detector to mimic the signature of double-beta decay to an excited state, along with preliminary analysis of these signals from an above ground detector array. [Preview Abstract] |
Sunday, April 17, 2005 9:18AM - 9:30AM |
H12.00005: A Low-Background Front-End Electronics Package for Germanium Spectrometers Todd Hossbach The Majorana project is a next-generation {$^{76}$Ge} neutrinoless double-beta decay search, using 57 isotopically- enriched segmented germanium crystals mounted in each of 9 modular cryostats. This configuration provides physical granularity which should reject most expected backgrounds. Greater effective granularity is planned via pulse-shape analysis. This requires $\sim$25~MHz bandwidth from the front- end electronics placed close to the crystals. Due to their proximity to the crystals, the front-end electronics must be radiopure. PNNL has developed a Low-background Front-end Electronics Package (LFEP) to support low-background spectrometer projects. The design and performance of the first LFEP boards is discussed, along with their potential application for Majorana. [Preview Abstract] |
Sunday, April 17, 2005 9:30AM - 9:42AM |
H12.00006: A High Purity Germanium Diode Operated as a Radiation Detector in Liquid Argon John L. Orrell Guided by the pioneering work of the GERDA Collaboration on next generation neutrinoless double beta decay experiments, we have begun an investigation of the operation of bare germanium (Ge) radiation detectors in liquid argon. Liquid argon (LAr) serves both as a cryogenic medium to cool the Ge crystal and as a scintillating veto shield. The veto shield has two distinct functions. First, the LAr tags and rejects radiation from external sources. Second, the LAr suppresses the Compton background arising from gamma-rays that only partly deposit their energy inside the Ge crystal. Current results from operating the Ge crystal as a radiation detector in LAr are presented. The value of this type of radiation detector is discussed regarding two potential applications. The first is the need for increasingly low-background, high-sensitivity radiation counters. The second is the next generation of neutrinoless double beta decay experiments currently under development. The Majorana Experiment is one such project that will benefit from this line of research. [Preview Abstract] |
Sunday, April 17, 2005 9:42AM - 9:54AM |
H12.00007: The depth-sensitivity relation (DSR) for underground laboratories Andrew Hime, Dong-Ming Mei Muon-induced background constrains the sensitivity of next generation underground low energy neutrino and dark matter experiments. Muon-induced background sources are (1) fast neutrons produced in the detector and surrounding materials (rock and shield materials) with a hard energy spectrum; (2) cosmogenic radioactivity created in the detector and surrounding materials; (3) stopping negative muon capture on nuclei produces neutrons and radioactive isotopes in the detector and surrounding materials; and (4) muons hit the detector due to a finite veto efficiency. Understanding and reducing these four muon-induced sources of background are essential to dark matter, double beta decay and $\theta_{13}$ experiments. An effective way to reduce such background is to increase the depth of the experimental site. Therefore, it is essential to study DSR for underground experiments. We proposed a unified approach to study muons, the muon-induced neutron flux, energy spectrum, angular distribution, multiplicity and lateral distribution with respect to the muon track for six underground laboratories. This study provides a comprehensive understanding of the muon-induced background level for underground laboratories and hence the reduction methods. [Preview Abstract] |
Sunday, April 17, 2005 9:54AM - 10:06AM |
H12.00008: The KATRIN Experiment: A precision tritium beta-decay measurement examining the mass of the neutrino Keith Rielage One of the most fundamental tasks facing nuclear and particle physics today is the determination of the absolute mass scale of neutrinos. The Karlsruhe Tritium Neutrino experiment (KATRIN) is a next generation tritium $\beta$ decay experiment capable of performing a high precision direct measurement of the absolute mass of the electron neutrino. The projected sensitivity of the experiment is $m(\nu_{e}) < 0.2$ eV (90\% C.L.). An overview of the experiment and its relative impact on cosmology, nuclear, and particle physics will be presented. KATRIN is scheduled to begin collecting data in 2008. Support for this project in the United States is provided by the DOE under contract DE-FG- 97ER41020. [Preview Abstract] |
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