Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session S4: Neutrinos - Low Energy II |
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Sponsoring Units: DNP DPF Chair: Christopher O’Shaughnessy, University of North Carolina Room: Holiday 3 |
Monday, April 13, 2015 1:30PM - 1:42PM |
S4.00001: Investigation of the backgrounds in the EXO-200 experiment Tamar Didberidze The Enriched Xenon Observatory EXO-200 experiment currently located at Waste Isolation Pilot Plant (WIPP) in New Mexico, which uses a 175 kg of isotopically enriched $^{136}$Xe, is designed to search for the neutrinoless double beta decay ($0\nu\beta\beta$) in $^{136}$Xe. The search for this type of decay requires a good understanding of background sources. I will present results of the background study done for the EXO-200 experiment. The study has been performed using a current EXO-200 low-background data and model to estimate the location and magnitude of background sources and compared to the radio assay results that were obtained before detector construction. [Preview Abstract] |
Monday, April 13, 2015 1:42PM - 1:54PM |
S4.00002: Validation of Pulse Shape Simulation for Ge detectors in the \textsc{Majorana Demonstrator} Benjamin Shanks The \textsc{Majorana Demonstrator} expects to begin searching for neutrinoless double beta decay using $^{76}$Ge-enriched detectors in 2015. The \textsc{Demonstrator} high purity germanium (HPGe) detectors are built in the p-type point contact (PPC) geometry. The electrode of a PPC detector is small and shallow, resulting in low intrinsic capacitance and bulk field strengths compared to the traditional coaxial HPGe configuration. These characteristics allow for discrimination of signal event candidates from background using pulse shape analysis (PSA). In order to fully understand the systematics and efficiencies of PSA cuts, the \textsc{Majorana} collaboration has developed a software package to simulate signal generation in PPC detectors. This code has been validated by comparing simulated pulses to the pulse shapes generated for given detectors using an external source. [Preview Abstract] |
Monday, April 13, 2015 1:54PM - 2:06PM |
S4.00003: Detector Characterization for the Majorana Demonstrator Thomas Gilliss The \textsc{Majorana Demonstrator} (MJD) is a neutrinoless double-beta decay ($0\nu\beta\beta$) search, in the isotope $^{76}\mathrm{Ge}$. Seeking measurement of the $0\nu\beta\beta$ lifetime, and exploration of additional physics, MJD employs high-purity Ge detectors possessing superior energy resolution down to a low threshold. Characterization of these p-type point contact detectors is essential to understanding the backgrounds and sensitivity of the experiment. Progress in characterizing MJD detectors will be presented. [Preview Abstract] |
Monday, April 13, 2015 2:06PM - 2:18PM |
S4.00004: Analysis of Cosmic Ray Backgrounds for Double-Beta Decay Experiments Mitchell Hughes In neutrinoless double-beta decay searches, such as EXO-200 and nEXO, cosmic ray muons constitute a significant background because they induce signals mimicking the rare decays under observation. Specifically, spallation neutrons produced by these muons may capture on detector and shielding components, producing long-lived unstable isotopes whose decays fall within the double-beta decay region of interest. Cosmogenic neutron backgrounds have been studied in EXO-200, which features an array of muon veto panels in addition to its primary detector, a time projection chamber enriched in 136-Xe. By selecting events occurring shortly after a muon panel trigger, a neutron-enriched data set may be composed and compared against Monte Carlo simulations of anticipated background contributions. Results and conclusions from this study will be discussed. [Preview Abstract] |
Monday, April 13, 2015 2:18PM - 2:30PM |
S4.00005: COHERENT First Steps for an Experimental Neutrino Program at the Spallation Neutron Source Grayson Rich The COHERENT Collaboration has been formed to make a first measurement of coherent neutral-current elastic neutrino-nucleus scattering (CENNS). Toward this, the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory has been identified as the premier facility for this measurement due to several factors, including: high neutrino flux, appropriate neutrino energies, SNS beam time structure for significant background reduction, and the ability to suitably place detector systems sufficiently near the neutrino source. An ongoing background measurement campaign at the SNS is identifying candidate locations and characterizing primary background signals for a CENNS detector system. The result of current efforts and their implications for a CENNS measurement at the SNS will be discussed. [Preview Abstract] |
Monday, April 13, 2015 2:30PM - 2:42PM |
S4.00006: Ion Studies Using Radon-222 in the EXO-200 Detector Erica Smith EXO-200 is a double beta decay experiment that uses liquid xenon enriched in xenon-136. While oscillation experiments have confirmed that neutrinos have mass, the nature of the neutrino remains elusive. The observation of neutrinoless double beta decay would confirm that the neutrino is Majorana, rather than Dirac. While studying double beta decay is the primary goal, EXO-200 can also perform many other robust analyses. Ion mobility and neutralization studies in liquid xenon detectors are particularly interesting, as the ability to extract barium ions from the detection medium and identify them would increase sensitivity to the double beta decay. We utilize the radon decay chain to perform these studies, which will be discussed in this talk. [Preview Abstract] |
Monday, April 13, 2015 2:42PM - 2:54PM |
S4.00007: Barium Tagging for nEXO in Liquid and Gas Xenon Scott Kravitz, Thomas Brunner, Dan Fudenberg nEXO is a next-generation multi-ton experiment currently under development to search for neutrinoless double-beta decay of Xe-136. A positive observation will determine the neutrino to be a Majorana particle. In order to greatly reduce backgrounds for this search, the nEXO collaboration is developing several techniques to recover and identify the decay daughter, Ba-136 (``barium tagging''). This technique may be available for a second phase of the nEXO detector and will improve the sensitivity to probe the neutrino mass scale beyond the inverted hierarchy. A setup to demonstrate Ba ion capture on a probe and subsequent identification through resonance ionization spectroscopy has been developed, and is being used to investigate possible probe substrates, including graphene. For a gas phase detector, appropriate for a later stage, a separate apparatus to extract Ba ions using an RF-only funnel has been constructed and demonstrates extraction of ions from high-pressure Xe to vacuum consistent with simulations. We will describe the status of these systems and the present results of this R\&D program. [Preview Abstract] |
Monday, April 13, 2015 2:54PM - 3:06PM |
S4.00008: Barium Tagging in Solid Xenon for nEXO Neutrinoless Double Beta Decay Tim Walton, Chris Chambers, Adam Craycraft, William Fairbank nEXO is a next-generation experiment designed to search for neutrinoless double beta decay of the isotope Xe136 in a liquid xenon time projection chamber. Positive observation of this decay would determine the nature of the neutrino to be a Majorana particle. Since the daughter of this decay is barium (Ba136), detecting the presence of Ba136 at a decay site (called ``barium tagging'') would provide strong rejection of backgrounds in the search for this decay. This would involve detecting a single barium ion from within a macroscopic volume of liquid xenon. This technique may be available for a second phase of the nEXO detector and sensitivity beyond the inverted hierarchy to neutrino oscillations. Several methods of barium tagging are being explored by the nEXO collaboration, but here we present a method of trapping the barium ion/atom (it may neutralize) in solid xenon (SXe) at the end of a cold probe, and then detecting the ion/atom by its fluorescence in the SXe. Our group at CSU has been studying the fluorescence of Ba in SXe by laser excitation, in order to ultimately detect a single Ba$+$/Ba in a SXe sample. We present studies of fluorescence signals, as well as recent results on imaging small numbers of Ba atoms in SXe, in a focused laser region. [Preview Abstract] |
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