Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session R6: Fundamental Symmetries III |
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Chair: Michael Huber, National Institute of Standards and Technology Room: Key 2 |
Monday, April 13, 2015 10:45AM - 10:57AM |
R6.00001: Measuring the antineutrino-beta Correlation in the Nab Experiment Aaron Sprow The Nab experiment will be performed at the Spallation Neutron Source to measure the electron-neutrino correlation parameter a and the Fierz interference term b for unpolarized neutron beta decays. We instrumented a segmented silicon detector with fast preamplifier channels and are developing a data acquisition system with digital pulse processing for this experiment. In collaboration with UCNB, we tested the system performance with neutron beta decay events and calibration sources. We will present an overview of the Nab experiment and results of these tests. [Preview Abstract] |
Monday, April 13, 2015 10:57AM - 11:09AM |
R6.00002: Measuring the beta-neutrino angular correlation in the $^6$He decay Yelena Bagdasarova, Alejandro Garicia, Ran Hong, Matthew Sternberg, Derek Storm, Erik Swanson, Frederik Wauters, David Zumwalt, Arnaud Leredde, Kevin Bailey, Peter Mueller, Thomas P. O'Connor, Xavier Flechard, Etienne Lienard, Oscar Naviliat-Cuncic We have set up an experiment to determine the electron-antineutrino correlation from $^6$He decay with the aim of searching for tensor currents in the electroweak interaction, which would constitute physics beyond the Standard Model. Our setup consists of a $^6$He production target connected to a laser cooling and magneto-optical trapping system which confines the atoms in a small region surrounded by detectors. The detection system entails a combination of a multiwire proportional chamber and scintillator (for the beta) plus an electric field guide and a microchannel plate detector (for the Li recoil ions). I will give an overview of the setup, a summary of expected systematic uncertainties, and the current status of the experiment. [Preview Abstract] |
Monday, April 13, 2015 11:09AM - 11:21AM |
R6.00003: Neutron Spin Rotation Measurements Murad Sarsour The neutron spin rotation (NSR) collaboration used parity-violating spin rotation of transversely polarized neutrons transmitted through a 0.5 m liquid helium target to constrain weak coupling constants between nucleons. While consistent with theoretical expectation, the upper limit set by this measurement on the rotation angle, d$\phi$/dz = [+1.7 $\pm$ 9.1(stat.) $\pm$1.4(sys.)]$\times 10^{-7}$ rad/m~\footnote{W. M. Snow et al., PRC \textbf{83}, 022501(R) (2011).}, was limited by statistical uncertainties. The NSR collaboration is preparing a new measurement to improve this statistically-limited result by about an order of magnitude. We are designing the new apparatus to operate on the new high flux NGC beam with increased phase-space at the National Institute of Standards and Technology (NIST) Center for Neutron Research. The upgraded apparatus with a room-temperature target will be tested at LANSCE in a measurement that will search for parity-conserving rotations from possible exotic neutron interactions. The design and readiness of the upgraded apparatus will be discussed in relation to its application in both measurements, and the current theoretical and experimental status of d$\phi$/dz in n-$^{4}$He will be reviewed. [Preview Abstract] |
Monday, April 13, 2015 11:21AM - 11:33AM |
R6.00004: Measurement of parity violation in $n+^{3}$He$\rightarrow p+t$ Christopher Coppola The hadronic weak interaction remains the least well-understood of the weak interactions. (There are several models with effective degrees of freedom characterizing its spin and isospin dependence.) Measuring the strength of this interaction is difficult due to the much larger strong interaction between nucleons. However, parity violation in few-body reactions allows isolation of weak contributions on the order of $10^{-7}$ from the strong background. The parity violating asymmetry in the reaction $n+^{3}$He is measured with a 3He target in the polarized pulsed neutron beam at the Spallation Neutron Source at Oak Ridge National Laboratory. It is necessary to calculate the proper geometry factors for this target chamber in order to extract the physics asymmetry from individual ion chamber signals. These factors are determined using a Monte Carlo simulation of the target chamber which includes effects due to correlations between different elements. [Preview Abstract] |
Monday, April 13, 2015 11:33AM - 11:45AM |
R6.00005: aCORN on the new NIST cold neutron beam line Md Hassan The aCORN experiment is measuring the electron-antineutrino angular correlation $a$ in neutron beta decay. Precision measurement of $a$ will improve the determination of the nucleon axial vector coupling constant $G_A$, and along with other decay parameters can be used to test the validity and self-consistency of the Standard Model and to explore the physics beyond it. The goal of the aCORN experiment is to determine $a$ to a relative accuracy of $1\%$. After two years on the NG-6 beam line at NIST, aCORN has now moved to a new higher flux NG-C beam line with some apparatus upgrades. The characterization of the new beam line and the upgrades to the apparatus will be presented. [Preview Abstract] |
Monday, April 13, 2015 11:45AM - 11:57AM |
R6.00006: GEANT4 Monte Carlo Modeling of the Nab Segmented Silicon Detectors Emil Frlez The Nab Collaboration has proposed to measure the correlation parameters $a$ and $b$ in neutron $\beta$-decay at Oak Ridge National Laboratory using a novel detector design. Two large area 2-mm thick hexagonal silicon detectors segmented into 127 pixels per detector will be used to detect the proton and electron from cold neutron decay. We present the GEANT4 simulation of the Si detector energy and timing responses both to the final state protons and electrons as well as the expected photon, cold neutron, and fast neutron backgrounds. The methods for an individual pixel energy gain calibrations and timing offset adjustments are presented. The expectations are compared to data acquired with a prototype detector at Los Alamos National Laboratory. [Preview Abstract] |
Monday, April 13, 2015 11:57AM - 12:09PM |
R6.00007: A precision measurement of the isospin dependence in the 2N and 3N short range correlation regions from the mirror nuclei $3H$ and $3He$ Dien Nguyen Short Range Correlations (SRCs) have been recognized as responsible for the high momentum tail of the nucleon momentum distribution. Several experiments at Jefferson Lab have exploited inclusive scattering to study these SRCs. In an upcoming tritium experiment (E12-11-112) at Jefferson Lab, we will perform a precision test of the isospin dependence of two- nucleon short range correlations using mirror nuclei: $3He$ and $3H$. The data taken at $x>2$ will also be used to study three-nucleon short range correlations. In this talk we will briefly present the motivation for this experiment as well as some of the experimental details and the expected results. In addition, we will discuss a method to check the absolute target thickness of both targets through elastic scattering. [Preview Abstract] |
Monday, April 13, 2015 12:09PM - 12:21PM |
R6.00008: Neutron interferometry in a temperature controlled vacuum environment for the search of dark energy and other precision experiments Parminder Saggu, D. Cory, D. Pushin, J. Nsofini, D. Sarenac, M. Huber, M. Arif, C. Shahi, R. Haun, M. Snow, K. Li, V. Skavysh, B. Heacock, A. Young The neutron interferometer is a sensitive tool to study neutron interactions in materials. Vibrations, acoustic waves, and temperature gradients can introduce phase shifts and reduce the SNR. Low neutron flux and an interest in measuring increasingly smaller phases makes it necessary for experiments to run over long periods of time. Hence, the interferometer needs to have excellent phase stability. It has been shown that by using Quantum Information Algorithms, one can make the interferometer insensitive to vibrations. In this work, we are trying to remove phase instability due to T variations. At the NCNR, the interferometer has been placed inside a vacuum chamber to decouple it from the environment and increase overall temperature stability. An Al vacuum chamber was machined and assembled to test the concept of an interferometer in vacuum and measure phase stability with the ultimate goal of using an interferometer in vacuum in an experiment searching for dark energy. [Preview Abstract] |
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