Bulletin of the American Physical Society
84th Annual Meeting of the APS Southeastern Section
Volume 62, Number 13
Thursday–Saturday, November 16–18, 2017; Milledgeville, Georgia
Session A3: Nuclear Physics I |
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Chair: T. Black, University of North Carolina Wilmington Room: MSU Building Donohoo Lounge |
Thursday, November 16, 2017 8:30AM - 8:42AM |
A3.00001: Recent Results from EXO-200 Timothy Daniels EXO-200 is a low-background time-projection chamber employing about 150kg of enriched liquid $^{\mathrm{136}}$Xe and located underground at the WIPP site outside Carlsbad NM. In its first phase of data-taking between 2011 and 2014, the experiment made the first observation of two-neutrino double-beta decay of $^{\mathrm{136}}$Xe, provided the most precise measurement of any two-neutrino half-life to date, and provided one of the most sensitive searches for neutrinoless double-beta decay. While the first phase ended with the 2014 fire and radiation events at WIPP, a second phase of data collection with upgrades including improved energy resolution began in 2016. Results including the first year of data with the upgraded detector will be shown. [Preview Abstract] |
Thursday, November 16, 2017 8:42AM - 8:54AM |
A3.00002: The measurement of neutron beta decay observables with the Nab spectrometer Stefan Baessler Nab, an experiment that allows studying unpolarized neutron beta decay at the Spallation Neutron Source at Oak Ridge National Lab, aims to determine a, the neutrino-electron correlation coefficient, and b, the Fierz interference term, with high precision. Such measurements provide opportunities to search for evidence of extensions to the Standard Model. Nab is presently being constructed, with beam readiness planned for mid 2018. I will discuss the experiment’s motivation and design, the planned modes of operation, and the performance of its components. [Preview Abstract] |
Thursday, November 16, 2017 8:54AM - 9:06AM |
A3.00003: The Electric Field in the Neutron Decay Region of the Nab. Huangxing Li The Nab collaboration will determine two parameters in free neutron beta decay: (a) the electron-antineutrino correlation coefficient $a$ to $|\delta a /a| \le 10^{-3}$ and (b) the Fierz interference term $b$ to $|\delta b| \le 3\times10^{-3}$. Part (a) will be done with a measurement of the two-dimensional electron energy and proton time-of-flight spectrum in the neutron beta decay. We will discuss the requirements for the electric field in the neutron decay region to achieve the desired experimental uncertainty. We will present our solution: an electrode system made from materials with low work function variations, and its characterization with a Kelvin probe. [Preview Abstract] |
Thursday, November 16, 2017 9:06AM - 9:18AM |
A3.00004: Fitting Methods in the Nab Experiment Wenjiang Fan The Nab collaboration aims to measure the electron-neutrino correlation parameter $a$ with a relative uncertainty of about $10^{-3}$, and the Fierz interference term $b$ with absolute uncertainty of $3\times 10^{-3}$ at the Spallation Neutron Source (SNS). In Nab, $a$ is determined by combined precise determinations of the electron energy and the proton time-of-flight. In this talk, we will present a fitting method to analyze $a$ and its uncertainties, as well as specific techniques developed to increase the fitting performance based on experimental scenario. [Preview Abstract] |
Thursday, November 16, 2017 9:18AM - 9:30AM |
A3.00005: Approximate approaches for nuclear weak interaction rates for astrophysics B.M. Anderson, G.W. Hitt, S.S. Gupta Nuclear weak interactions, like beta decay and electron capture, are important inputs for modeling explosive astrophysical events. In the allowed approximation, nuclear weak interactions proceed as either Fermi or Gamow Teller (GT) processes where the spins of the electron and neutrino are either anti-parallel or parallel, respectively. In the GT case, transition probability is spread over many final states in the daughter nucleus, with each probability determination requiring numerical integration of the available phase space. Developing a fast and accurate method for calculating each contribution to the total decay rate would provide reliable weak rate libraries for astrophysical modelers. The integrand for the phase space includes the classical statistical factor, a coulomb correction, and the Fermi Dirac distribution of continuum electrons in the stellar material. In this talk, we specifically examine the phase space integration and discuss various approximations to the Coulomb correction, comparing computational speed and numerical accuracy. [Preview Abstract] |
Thursday, November 16, 2017 9:30AM - 9:42AM |
A3.00006: Measurement of the MUSE Scattered-Particle-Scintillators Time Resolution Lin Li The proton-radius puzzle, which arises from the discrepancy between measurements of the proton charge radius using muonic and electronic probes, has led to theoretical and experimental investigations. The MUon Scattering Experiment (MUSE) at the Paul Scherrer Institute (PSI) will address the puzzle by determining the proton charge radius with electron- and muon-scattering measurements off the proton with high precision. The MUSE scattered-particle scintillators, built at University of South Carolina, are part of the readout trigger and serve as time-of-flight detectors for particle identification. The system is comprised of 18 120-cm long detectors in a front wall and 28 220-cm long detectors in a rear wall. In this talk I will discuss a testing procedure for the TOF system using cosmic rays and six detector elements to determine their time resolutions. With this procedure, an average time resolution of better than 60 ps over the full length of a long detector bar (6 cm $\times$ 6 cm $\times$ 220 cm) and better than 50 ps for a short bar (6 cm $\times$ 3 cm $\times$ 120 cm) was demonstrated. The time resolutions are well within the requirements of the experiment. [Preview Abstract] |
Thursday, November 16, 2017 9:42AM - 9:54AM |
A3.00007: The MUSE Experiment and Proton Radius Puzzle: Design and Status of LH$_2$ Cryotarget Priyashree Roy, Noah Steinberg, Luc LePottier, Richard Raymond, Wolfgang Lorenzon A fundamental challenge faced by the scientific community is to resolve the proton radius puzzle: the $7\sigma$ discrepancy observed between muon spectroscopy and atomic measurements of the proton radius. The discrepancy, if real, could point to interesting new physics. The MUon Scattering Experiment (MUSE), which will take place at the Paul Scherrer Institute in Switzerland, will play an instrumental role towards resolving this puzzle since it will be the first muon elastic scattering experiment at low $Q^{2}$ of about $0.0016-0.08$~GeV$^{2}$ and the first to perform simultaneous elastic scattering measurements using both muons and electrons. This will allow a direct comparison of the proton radius from the two leptonic probes to a sub-percent level. An essential and arguably the most complex part of MUSE is the liquid hydrogen (LH$_{2}$) cryotarget system. Dictated by physics needs, the cryotarget system needs to satisfy many requirements, including a vertically movable target ladder consisting of three more targets in addition to the LH$_{2}$ target housed inside a vacuum chamber and large vacuum windows on both sides of the beamline. Here we report on the design and status of the MUSE cryotarget system, and our technique to fabricate the LH$_{2}$ target cell. [Preview Abstract] |
Thursday, November 16, 2017 9:54AM - 10:06AM |
A3.00008: Studies of new GaInP based Geiger-mode APD arrays Grace Cummings, Robert Hirosky Devices composed of wide band gap semiconductors such as GaInP have the theoretical potential to withstand many orders of magnitude larger radiation exposures compared to silicon. The demonstration of functional devices with new semiconductor materials and epitaxies is a prerequisite to evaluating this potential. We will discuss results from measurements of performance properties and radiation damage studies of two recent generations of prototype devices and discuss plans for future work. [Preview Abstract] |
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