Bulletin of the American Physical Society
2013 Fall Meeting of the APS Division of Nuclear Physics
Volume 58, Number 13
Wednesday–Saturday, October 23–26, 2013; Newport News, Virginia
Session DB: Mini-Symposium on Searches for Double Beta Decay II |
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Chair: Werner Tornow, Duke University Room: Pearl Ballroom I |
Thursday, October 24, 2013 10:30AM - 10:42AM |
DB.00001: Stringed Planar-detectors for Investigation of Rare Event Physics Wenzhao Wei, Dongming Mei, Chao Zhang In the detection of rare event physics with HPGe detectors, conventional P-type Point Contact (PPC) or coaxial detectors have no capability of discriminating electron/nuclear recoils. The CDMS-type bolometers, which possess great electron/nuclear recoils discrimination, must be operated in milli-kelvin temperature range with diffusion refrigerator at high price. Alternatively, a new idea of using great granularity and plasma time difference in pulse shape to discriminate nuclear recoils from electronic recoils with conventional germanium detectors is discussed in this paper. Stringed planar germanium detectors have been designed in a Geant4-based Monte Carlo simulation in which radiogenic backgrounds from $^{60}$Co, $^{40}$K, $^{238}$U, $^{232}$Th, and (alpha,n) neutrons have been studied. We show the anticipated sensitivity of this new detector array for detecting rare event physics including neutrinoless double-beta decay. [Preview Abstract] |
Thursday, October 24, 2013 10:42AM - 10:54AM |
DB.00002: Radio-purity design elements for the MAJORANA DEMONSTRATOR Christopher O'Shaughnessy The \textsc{Majorana} collaboration is building an experiment to search for neutrinoless double beta ($0\nu\beta\beta$) decay of $^{76}$Ge. The expected signal for half-lifes of $10^{26}$ to $10^{27}$ years will be a few counts/tonne-year. This puts very tight constraints on the allowable background radiation in the vicinity of the detector. Designing an experiment that will have a sensitivity to neutrino masses in the in the range dominated by the inverted hierarchy, 15 -- 50 meV, will require a source with tonne-scale mass and backgrounds contributions in the region of interest of $\sim$ one count per tonne-year. The added constraints from radio-purity often render the standard solutions to common design problems untenable. Here we will present some of the ultrapure vacuum and cryogenic technologies being developed for the Majorana experiment. While developed for $0\nu\beta\beta$ these design elements can be extended to all manner of low background experiments. [Preview Abstract] |
Thursday, October 24, 2013 10:54AM - 11:06AM |
DB.00003: Measuring fast neutrons with large liquid scintillator for ultra-low background experiments Chao Zhang, Dongming Mei, Patrick Davis, Brian Woltman, Frederick Gray Characterizing neutron background is extremely important to the success of rare event physics research such as neutrinoless double-beta decay and dark matter searches. Measuring the energy spectrum of fast neutrons for an underground laboratory is difficult and it requires intensive R{\&}D for a given technology. We developed a neutron detector that is constructed using an aluminum tube with one meter long and 5 inch in diameter filled with 12 liter liquid scintillators(EJ-301). The inner surface of the tube is painted with specular reflector and there are two 5" PMTs(Hamamatsu H4144) attached to both ends. The detector is calibrated with cosmic muons and radioactive sources. Good neutron/gamma discrimination is found from few MeV up to hundred MeV. We report the result for the measurements of muons and fast neutrons in Soudan Mine for over one year data. [Preview Abstract] |
Thursday, October 24, 2013 11:06AM - 11:18AM |
DB.00004: Testing the Ge detectors for the \textsc{Majorana} \textsc{Demonstrator} Wenqin Xu High purity germanium (HPGe) crystals will be used for the \textsc{Majorana} \textsc{Demonstrator}, where they serve as both the source and the detector for neutrinoless double beta decays. It is crucial for the experiment to understand the performances of the HPGe crystals. A variety of crystal properties are being investigated, including both basic properties such as energy resolution, efficiency, uniformity, capacitance, leakage current and crystal axis orientation, as well as more sophisticated properties, \textit{e.g.} pulse shapes and dead layer and transition layer distribution. In this talk, we will present our measurements that characterize the HPGe crystals. We will also discuss the experiment's simulation package for the detector characterization setup, where additional information is learned from data-simulation comparisons. [Preview Abstract] |
Thursday, October 24, 2013 11:18AM - 11:30AM |
DB.00005: Calibration of the CUORE Detector Array Kyungeun Lim, Adam Dally, Larissa Ejzak, Karsten Heeger, Reina Maruyama, Lauren Wielgus, Tom Wise, Pingchuan Zhao CUORE is a ton-scale cryogenic detector that will use an array of 988 $\textrm{TeO}_{2}$ bolometers to search for neutrinoless double-beta decay of ${}^{130}\textrm{Te}$. Calibration of the detector is essential to determine the energy scale, especially near the Q-value of the nuclear transition where the neutrinoless double-beta decay is expected as a monochromatic peak. The CUORE detector calibration system has been designed and built to uniformly irradiate the entire volume with low-temperature sources. It is necessary to mechnically cool the sources to 4 K to maintain the bolometers at their working points. In this talk I will give an overview of the detector calibration system and present the first results from its commissioning in the cryostat. [Preview Abstract] |
Thursday, October 24, 2013 11:30AM - 11:42AM |
DB.00006: Study of pulse shape discrimination techniques for the MAJORANA DEMONSTRATOR Susanne Mertens The MAJORANA DEMONSTRATOR will perform a search for neutrinoless double-beta decay in 76Ge. The experiment is currently under construction at the Sanford Underground Laboratory in South Dakota, USA. It will use an array of 40 kg of germanium detectors, up to 30 kg of which will be enriched to 86\% of 76Ge. A major goal of the demonstrator is to reach a background level necessary to prove the feasibility of a tonne-scale experiment. This talk will discuss the performance of a pulse shape discrimination technique that will help reduce the background to the required level. [Preview Abstract] |
Thursday, October 24, 2013 11:42AM - 11:54AM |
DB.00007: Waveform Simulation for Pulse Shape Analysis Validation Benjamin Shanks Background reduction techniques are critical for successful detection of rare events. To facilitate its search for neutrinoless double beta ($0\nu\beta\beta$) decay, the \textsc{Majorana Demonstrator} aims to achieve a background goal of $<3$ counts/tonne-year in the $4$-keV-wide region of interest. The p-type point contact germanium detectors used in the \textsc{Demonstrator} are sensitive to the distribution of interaction sites in the crystal bulk. The signal generated by single-site events, such as the {$0\nu\beta\beta$} decay signal, can be distinguished from multi-site background events using a pulse shape analysis (PSA) algorithm. The details of a simulation-based framework to validate PSA techniques are presented here. [Preview Abstract] |
Thursday, October 24, 2013 11:54AM - 12:06PM |
DB.00008: Results from EXO-200 Andrea Pocar The Enriched Xenon Observatory (EXO) is an experimental program searching for neutrinoless double beta decay using Xe-136. Observation of this lepton number violating decay would demonstrate that neutrinos are Majorana particles and allow determination of the absolute neutrino mass scale. The first stage of the experiment, EXO-200, consists of an extremely low background time projection chamber containing $\sim$150 kg of liquid xenon enriched to 80{\%} Xe-136. EXO-200 has been taking data continuously since May 2011 and has previously reported the first observation of two neutrino double beta decay (2vbb) in Xe-136 as well as stringent constraints on the neutrinoless mode. We will present recent results from EXO-200, including an improved measurement of the 2vbb half-life in Xe-136, which is the most precisely measured half-life for any 2vbb decay reported to date and give a status report on the 0vbb search. As time allows, we will discuss the status of nEXO, the planned multi-tonne scale successor to EXO-200. [Preview Abstract] |
Thursday, October 24, 2013 12:06PM - 12:18PM |
DB.00009: Ba-Tagging for EXO Daniel Fudenberg In order to perform a background-free measurement of neutrinoless double-beta decay in $^{136}$Xe, the EXO collaboration is developing techniques to recover and identify the decay daughter, $^{136}$Ba, from both liquid and gas phase detectors. For a gas phase TPC detector, an apparatus is under development to extract Ba ions using a radio-frequency funnel. The extraction of ions from high-pressure Xe to vacuum was demonstrated to be consistent with simulations. A next step is a charge-to-mass selective detection upgrade, ultimately to be replaced by optical spectroscopic identification. For use in a liquid phase TPC detector, Ba ion capture on a metallic probe and identification utilizing Resonance Ionization Spectroscopy has been demonstrated in vacuum. This achieves Ba identification through both optical and mass spectroscopy. In a next step, Ba ion capture will be implemented in liquid Xe. [Preview Abstract] |
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