Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session HC: Mini-Symposium: Neutrino Properties and Nuclear Physics V |
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Chair: William Louis, Los Alamos National Laboratory Room: Jewett Ballroom A-B |
Saturday, October 25, 2008 2:00PM - 2:12PM |
HC.00001: What's Needed, What's Available, Where to Find it, What's Not Available and How to Go About it? Werner Tornow I briefly summarize some of the nuclear data needed for background correction of existing and future data in neutrino physics studies, double-beta decay and dark-matter searches. The focus is on neutron induced background which can mimic the signal of interest. Here, reactions induced by low-energy neutrons ($<$30 MeV or so) are of major concern, while higher energy neutrons produce charged- particle events which can be more easily distinguished from the events of interest. Although experimental data for the differential elastic scattering cross section do not exist for all nuclei of interest, they can fairly accurately be calculated using existing models. Inelastic scattering differential cross-section data and (n,2n) reaction data are more of a problem because here both data and calculations are scarce or even completely missing for some of the nuclei of interest. Neutron induced reactions with charged-particles in the exit channel tend to be less of a problem for neutrino physics, double-beta decay and dark-matter studies due to their well defined signature. I will conclude by mentioning the existing facilities where some of the missing data can potentially be measured. [Preview Abstract] |
Saturday, October 25, 2008 2:12PM - 2:24PM |
HC.00002: Neutron-Induced Partial $\gamma$-ray Cross-Section Measurements on Cu, Ge and Pb E. Kwan, J.H. Esterline, B. Fallin, C.R. Howell, A. Hutcheson, M.F. Kidd, A. Tonchev, W. Tornow, H.J. Karwowski, J.H. Kelley, D.M. Mei In high-precision low-statistic measurements such as those carried out in deep underground low-background environments, naturally-occurring radiation can obscure the region of interest. For example, energetic neutrons produced from natural radioactivity or muon-induced reactions will interact with the experimental apparatus producing a continuous background. A survey of neutron-induced $\gamma$-ray transitions in $^{nat}$Cu, enriched $^{76}$Ge, and $^{nat}$Pb from 150-4000 keV was carried out at TUNL using pulsed mono-energetic neutron beams, with an emphasis on the region around 2039 keV where the $0\nu\beta\beta$ decay peak of $^{76}$Ge is expected to appear. Transitions at 2041, 2615, and 3062 keV in the shielding materials of Pb and Cu may either directly interfere with the $^{76}$Ge $0\nu\beta\beta$ peak at 2039 keV or may produce nearby escape peaks. The rates at which these background peaks occur are needed to determine whether events due to $0\nu\beta\beta$ decay are observed and whether neutrinos are indeed their own anti-particles. [Preview Abstract] |
Saturday, October 25, 2008 2:24PM - 2:36PM |
HC.00003: Radionuclide Production Cross Sections from 800-MeV Proton Interactions in Ge and Mo Targets B. Quiter, E.B. Norman, A.R. Smith, S.A. Wender, R.C. Haight, A.F. Barghouty Minimization of radioactive backgrounds is critical for experiments attempting to measure neutrinoless double beta decay (0$\nu \beta \beta)$. To estimate cosmic ray-induced radionuclide production in 0$\nu \beta \beta $ experiments, we have irradiated targets composed of natural isotopic composition molybdenum and germanium with 800 MeV protons at the Los Alamos Neutron Science Center (LANSCE). The targets were counted with high-purity germanium detectors at Lawrence Berkeley National Laboratory intermittently from 2 weeks to 1 year after irradiation to determine the cumulative cross sections for radionuclide production. In total, 30 radioactive products were observed in the Mo target and 20 in the Ge target. Our experimental results are compared with the predictions from the semi-empirical Silberberg and Tsao code as well as previously reported Mo experimental data. [Preview Abstract] |
Saturday, October 25, 2008 2:36PM - 2:48PM |
HC.00004: Cosmic ray contribution to the Cuoricino background Laura Kogler CUORE is a proposed next-generation bolometric experiment to search for neutrinoless double beta decay in 130Te. Cuoricino is the recently finished prototype experiment for CUORE. To reach its goal, CUORE must achieve a background level of less than 0.01 counts/kev/kg/year. One potential source of background comes from cosmic ray muons. The experiment is located at a depth of 3500 m.w.e. in the Gran Sasso National Laboratories in Italy, where there is an average muon flux of approximately 1 per square meter per hour. We have investigated the contribution of cosmic ray muons to the background of Cuoricino by installing plastic scintillator muon counters outside of the detector to directly measure the correlation between intercepted muons and recorded events in the detector. We will present the results of this analysis and the implications for Cuoricino and CUORE. [Preview Abstract] |
Saturday, October 25, 2008 2:48PM - 3:00PM |
HC.00005: A Model of Nuclear Recoil Scintillation Efficiency in Noble Liquids Dongming Mei, Zhongbao Yin, Laura Stonehill, Andrew Hime Scintillation efficiency of low-energy nuclear recoils in noble liquids plays a crucial role in interpreting results from some direct searches for Weakly Interacting Massive Particle (WIMP) dark matter. However, the cause of a reduced scintillation efficiency relative to electronic recoils in noble liquids remains unclear at the moment. We attribute such a reduction of scintillation efficiency to two major mechanisms: 1) energy loss and 2) scintillation quenching. The former is commonly described by Lindhard's theory and the latter by Birk's saturation law. We propose to combine these two to explain the observed reduction of scintillation yield for nuclear recoils in noble liquids. Birk's constants $kB$ for argon, neon and xenon determined from existing data are used to predict noble liquid scintillator's response to low-energy nuclear recoils and low-energy electrons. We find that energy loss due to nuclear stopping power that contributes little to ionization and excitation is the dominant reduction mechanism in scintillation efficiency for nuclear recoils, but that significant additional quenching results from the nonlinear response of scintillation to the ionization density. [Preview Abstract] |
Saturday, October 25, 2008 3:00PM - 3:12PM |
HC.00006: Nuclear Quenching in Gaseous Argon Kareem Kazkaz, Adam Bernstein, Michael Foxe, Christian Hagmann, Igor Jovanovic, Wolfgang Stoeffl, Celeste Winant In many media and with varying degrees of efficiency, nuclear recoils can induce ionization and/or scintillation. These nuclear recoil signatures can be used in dark matter searches and neutrino physics experiments, and to detect neutrons. To understand the behavior of the ionization process induced by nuclear recoils, nuclear quenching factors must be measured at various energies to properly reconstruct the recoil event. In this context, the quench factor is defined as the ratio of the number of electron-ion pairs produced by a nuclear recoil of a given energy to the number produced by an electron recoil of the same energy. Taking advantage of a unique 60 keV portable neutron source developed by LLNL, we will present latest results from our efforts to measure the nuclear quenching factor in gaseous argon at the lowest energy yet attempted. We also discuss using nuclear recoils in liquid argon to search for coherent neutrino scatters. [Preview Abstract] |
Saturday, October 25, 2008 3:12PM - 3:24PM |
HC.00007: Measurements of $F_2$ and $R=\sigma_L/\sigma_T$ on Deuterium and Nuclei in Nucleon Resonance Region Ya Li Jefferson Lab E02-109/E04-001 study the longitudinal-transverse (L-T) separated structure functions $F_1$, $F_2$, $F_L$, and the ratio of longitudinal and transverse cross sections $R=\sigma_L/ \sigma_T$ from deuterium and other nuclear targets (Carbon, Iron and Aluminum) in nucleon resonance region. The experiments will provide the first global survey of the L-T separated quantities of nuclei in resonance region. In addition, these data will be used as input vector form factors in a future analysis of neutrino data. After a brief presentation of the motivation of the experiments and associated analysis details, the preliminary results will be presented. [Preview Abstract] |
Saturday, October 25, 2008 3:24PM - 3:36PM |
HC.00008: A Measurement of $F_2$ and $R=\sigma_L/\sigma_T$ on Nuclear targets in the Nucleon Resonance Region Vahe Mamyan Jefferson Lab Experiment E04-001 used the Rosenbluth technique to measure $R=\sigma_L/\sigma_T$ and $F_2$ on deuterium and nuclear targets. This experiment was part of a multilab effort[1] to investigate quark-hadron duality and the electromagnetic and weak structure of the nuclei in the resonance region. In addition to the studies of quark-hadron duality in electron scattering on nuclear targets, these data will be used as input form factors in future analysis of neutrino data which investigate quark-hadron duality of the nucleon and nuclear axial structure functions. An important goal of this experiment is to provide precise data which to allow a reduction in uncertainties in neutrino oscillation parameters for neutrino oscillation experiments (K2K, MINOS). This inclusive experiment was completed in July 2007 at Jefferson Lab where the Hall C High Momentum Spectrometer detected the scattered electron. Measurements were done in the nuclear resonance region ($1 < W^2 < 4 GeV^2$) spanning the four-momentum transfer range $0.5 < Q^2 < 4.0 (GeV^2)$. Data was collected from four nuclear targets: C, Al, Fe and Cu. After a brief presentation of the motivation of the experiment and its experimental and analysis details, the preliminary results will be presented. [1] Fermilab Minerva Experiment[http://minerva.fnal.gov/] [Preview Abstract] |
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