Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session R15: Neutrino Physics |
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Sponsoring Units: DNP Chair: Andrew Hime, Los Alamos National Laboratory Room: Hyatt Regency Jacksonville Riverfront City Terrace 11 |
Monday, April 16, 2007 10:45AM - 10:57AM |
R15.00001: Measuring $^8B$ Solar Neutrino Elastic Scattering with KamLAND Lindley A. Winslow The precision measurement of $^{8}B$ solar neutrinos elastic scattering in Super KamiokaNDE is one of the key measurements supporting the LMA + MSW solution to the solar neutrino problem. Though much smaller than Super KamiokaNDE, KamLAND is sensitive to $^{8}$B elastic scattering events and would expect to detect $3.3\pm0.5$ events per kilo-ton day above 5.5 MeV in the case of no oscillations. Since KamLAND uses scintillation light instead of Cerenkov light to detect these events the backgrounds and experimental methodology is different. The main backgrounds are natural radioactivity in the liquid scintillator, external high energy gammas, and light radioactive nuclei from muon spallation. The radiogenic backgrounds from natural U and Th above 5.5 MeV are negligible. The background from high energy gamma rays from the stainless steel supporting KamLAND and the surrounding rocks can be shielded by choosing an appropriate fiducial volume. The most problematic background is from short lived light nuclei made by muon spallation mainly $^{11}Be$ which has a $\tau_{1/2}=13.6s$ and an endpoint of 11.5 MeV. The production rate of $^{11}Be$ is not well understood but preliminary analysis shows that the measurement of $^{8}B$ neutrinos elastic scattering is possible with KamLAND. I will describe how KamLAND can be used to measure the solar neutrino flux from the decay of $^{8}B$ [Preview Abstract] |
Monday, April 16, 2007 10:57AM - 11:09AM |
R15.00002: The Majorana Neutrinoless Double-beta Decay Experiment. Reyco Henning Neutrinoless double-beta decay is the only practical process that probes the Majorana nature of the neutrino. The half-life of the decay could also provide a measurement of the absolute neutrino mass-scale. The Majorana experiment proposes to search for the neutrinoless double-beta decay of $^{76}$Ge using an array of 86{\%} enriched HPGe detectors. Majorana proposes to field 57 1.1 kg. detectors during its first phase. This talk will discuss the radio-pure materials, pulse-shape discrimination, crystal segmentation, time-correlation, a deep underground location and other techniques employed to reduce backgrounds in Majorana. This talk will cover the Majorana detector design and anticipated physics reach as well. [Preview Abstract] |
Monday, April 16, 2007 11:09AM - 11:21AM |
R15.00003: Multiple-Isotope Comparison for Determining 0$\nu\beta\beta$ Mechanisms Victor M. Gehman, Steven Elliott We present a technique for estimating the number of future 0$\nu\beta\beta$ results using several distinct nuclei to optimize the physics reach of upcoming experiments. We use presently available matrix element calculations and simulated sets of predicted 0$\nu\beta\beta$ measured rates in multiple isotopes to estimate the required precision and number of experiments to discern the underlying physics governing the mechanism of the process. Our results indicate that 3 (4) experimental results with total uncertainty (statistical, systematic, theoretical) of less than $\sim 20\%$ ($\sim 40\%$) can elucidate the underlying physics. If the theoretical ({\it i.e.} matrix element) uncertainty contribution is below $\sim 18\%$, then 3-4 experimental results of $\sim 20\%$ precision (statistical and systematic) are required. These uncertainty goals can be taken as guidance for the upcoming theoretical and experimental programs. [Preview Abstract] |
Monday, April 16, 2007 11:21AM - 11:33AM |
R15.00004: Neutron-Induced Background for Double-Beta Decay Experiments V.E. Guiseppe, S.R. Elliott, A. Hime, R.O. Nelson, N. Fotiadis, M.J. Devlin, R.C. Haight, D.-M. Mei, C. Keller, W. Tornow, A.P. Tonchev, A. Chyzh, J.H. Esterline, B. Fallin, C.R. Howell, A. Hutcheson, H.J. Karwowski, J.H. Kelley, M. Kidd Measurements of neutron excitation in lead, copper, and germanium at TUNL and LANSCE in search of specific excited state decays are important in understanding neutron-induced background in some double-beta decay experiments. The nucleus, in a highly excited state, decays via a $\gamma$ cascade to the ground state and produces background that may contribute to the next generation of double-beta decay experiments designed to reach the sensitivity of the atmospheric neutrino mass scale (45 meV). Measuring and understanding the high-energy neutron excitations of the shielding and detector materials for neutrinoless double-beta decay experiments are crucial for interpreting results and establishing shielding requirements. Determination of partial $\gamma$-ray cross sections provides useful data for benchmarking Monte Carlo simulation of background events. Some specific excited state transitions, such as the $\frac{5}{2}^+$ to $\frac{5}{2}^-$ decay in $^{207}$Pb and the 1$^-$ to 1$^+$ decay in $^{206}$Pb, are potentially troublesome for Ge-based double-beta decay experiments. [Preview Abstract] |
Monday, April 16, 2007 11:33AM - 11:45AM |
R15.00005: The KATRIN Neutrino Mass Experiment Joseph Formaggio Over the past decade, experiments studying neutrinos from atmospheric, solar, and reactor sources have shown conclusively that neutrinos change flavor and, as a consequence, have a small but finite mass. Yet, the scale of neutrino masses remains an open question that is of great importance for many areas of physics. The Karlsruhe Tritium Neutrino (KATRIN) experiment is the next generation tritium beta decay experiment with sub-eV sensitivity to make a direct, model independent measurement of the electron neutrino mass. The principle of the experiment is to look for a distortion at the endpoint of the electron energy spectrum from tritium beta decay. KATRIN will reach a final sensitivity of 200 meV at 90\% C.L. on the absolute neutrino mass scale. This talk will provide an overview of the experiment as well as highlight some of the year's achievements in its construction. [Preview Abstract] |
Monday, April 16, 2007 11:45AM - 11:57AM |
R15.00006: Commissioning Studies with the KATRIN Pre-Spectrometer Michelle Leber The \underline {Ka}rlsruhe \underline {Tri}tium \underline {N}eutrino experiment (KATRIN) plans to precisely measure the beta-decay electron energy spectrum near the tritium decay endpoint in order to directly probe the mass of neutrinos in the degenerate region. The highest energy beta-decay electrons from gaseous molecular tritum will be energy analyzed using a 10 m diameter Magnetic Adiabatic Collimation and Electrostatic (MAC-E) spectrometer. This main spectrometer is preceded by a similar but smaller pre-spectrometer that serves as a pre-filter to reduce the number of electrons that enter the main spectrometer. We will briefly discuss the design requirements for the spectrometers including vacuum requirements, energy resolution, and transmission properties. The spectrometers also include inner electrodes to further reduce backgrounds. Construction of the pre-spectrometer was recently completed and we will report on the preliminary studies of this system. [Preview Abstract] |
Monday, April 16, 2007 11:57AM - 12:09PM |
R15.00007: Calibrating the KATRIN tritium beta-decay experiment Benjamin Monreal The Karlsruhe Tritium Neutrino experiment (KATRIN) is a large tritium beta-decay experiment which will determine the mass of the electron neutrino with a sensitivity of $m({\nu_e}) < 0.2$ eV (90\% CL). This measurement requires a high level of stability in all spectrometer systems, including the source, the electromagnetic filter, and the detector, as well as a detailed measurement of the scattering cross sections of electrons on molecular tritium. We will give an overview of the experiment, then discuss several sources of systematic error and the calibrations which are planned to reduce them. These include Am-Co detector stability monitors and spectrometer testing with 83Kr. In particular, we will discuss the pulsed electron gun that both calibrates the spectrometer transmission and measures the electron-T$_2$ scattering cross sections. [Preview Abstract] |
Monday, April 16, 2007 12:09PM - 12:21PM |
R15.00008: Creating Unbinned, Nonparametric PDFs using the Kernel Estimation Method Stanley Seibert Data from the first two operational phases of the Sudbury Neutrino Observatory are currently being reanalyzed at an energy threshold of 3.5 MeV. Both integral $^8$B neutrino fluxes and differential fluxes as a function of energy will be obtained through a joint maximum likelihood fit of both data sets. Overall uncertainties will be reduced through increased event statistics, as well as the inclusion of systematics which are correlated between the two phases as free parameters in the fit. Floating systematic parameters during fitting can present a variety of technical challenges when working with binned PDFs. This talk describes the kernel estimation technique for generating analytic, unbinned, multidimensional PDFs from Monte Carlo event data sets, as it has been applied to the SNO analysis. Several optimizations are presented which make kernel estimation practical for use with large data sets, and the method is compared to traditional binned PDF techniques. [Preview Abstract] |
Monday, April 16, 2007 12:21PM - 12:33PM |
R15.00009: External Beta-Gamma Background Tails Analysis in SNO Christopher Tunnell The SNO collaboration is working on lowering its analysis energy threshold. To do this one must fully understand the background physics at these energies. At our anticipated threshold, MeV-order decay products from the Uranium and Thorium chain become increasingly important due to misreconstruction of these events, which allows them to pass our energy and fiducial volume cuts. Accordingly, one must study sources of beta-gamma radioactivity outside of our analysis region by expanding the fiducial volume. Using a newly developed energy fitter, position fitter, Monte Carlo simulations and new analysis techniques, the external backgrounds will be fit and the anticipated number of $\beta$-$\gamma$ external backgrounds in our signal box extrapolated. [Preview Abstract] |
Monday, April 16, 2007 12:33PM - 12:45PM |
R15.00010: Pulse Shape Simulation for the NCD Phase of the Sudbury Neutrino Observatory Noah Oblath In the third phase of the Sudbury Neutrino Observatory (SNO) experiment an array of $^3$He proportional counters has been used to make a measurement of the total solar neutrino flux. This Neutral-Current Detection (NCD) Array detected the neutrons from the neutral-current interaction of neutrinos with deuterium. Before we can determine the neutrino flux we must separate the neutron-capture pulses from the background pulses due to alpha particles. We have created a unique, detailed simulation of the current pulses from the proportional counters that includes energy straggling, ion drift, electron diffusion, space charge, and electronics effects. We intend to use the simulation to fit the data pulses to separate neutron-capture and alpha pulses. With this method the differences between pulse characteristics can be associated directly with the physical mechanisms of track formation and motion in the counter gas. The detailed pulse simulations will also be used as reference data sets for other methods of signal extraction. This work is conducted under DOE grant DE-FG02-97ER41020. [Preview Abstract] |
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