Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session JH: Electroweak Interactions and Fundamental Symmetries |
Hide Abstracts |
Chair: Nadia Fomin, University of Tennessee Room: Pavilion Ballroom C |
Saturday, October 15, 2016 10:30AM - 10:42AM |
JH.00001: Production and trapping efficiency improvements for the He-6 experiment Yelena Bagdasarova, Alejandro Garcia, Joben Pedersen, Eric Smith, Derek Storm, Erik Swanson, Kevin Bailey, Ran Hong, Arnaud Leredde, Peter Mueller, Tom P. O'Connor, Xavier Flechard, Andreas Knecht, Oscar Naviliat-Cuncic, Frederik Wauters The He-6 experiment at the University of Washington aims to precisely measure the beta-neutrino angular correlation ($a_{\beta\nu}$) in the beta decay of He-6, a parameter that is particularly sensitive to tensor-like currents in the electroweak interaction. The experiment is based on a coincidence detection of the beta and recoil ion emitted from laser trapped He-6 and seeks to ultimately measure $a_{\beta\nu}$ to the $0.1\%$ level. In the last year, major efforts have been put into increasing the data acquisition rate in order to obtain statistics for a $1\%$ measurement of $a_{\beta\nu}$ . The focus was on improving the the stability of the He-6 production target and increasing trapping efficiency with upgrades to the laser system. These improvements and the current status of the experiment, along with resulting data and calibration improvements, will be discussed. [Preview Abstract] |
Saturday, October 15, 2016 10:42AM - 10:54AM |
JH.00002: UCNB: Precise Measurement of the Neutrino Asymmetry from Polarized $\beta$-decay Aaron Sprow The UCNB experiment aims to measure the neutrino asymmetry, $B$, from free neutron decay using the ultracold neutron source at the Los Alamos Neutron Science Center. A precise measurement of $B$ yields insight into physics such as right-handed currents, and provides a sensitive channel to probe for exotic scalar and tensor couplings. By instrumenting the existing UCNA spectrometer with thick, highly-segmented silicon detectors, coincident electron and proton pairs from UCN decays have been directly measured, allowing for a determination of $B$. Presented here will be an analysis of the 2015-2016 data and a study of the potential sources of systematic error for a measurement of the $B$ coefficient. The goal of the UCNB experiment is to determine the neutrino asymmetry to a precision of $\delta B/B \approx 10^{-3}$. [Preview Abstract] |
Saturday, October 15, 2016 10:54AM - 11:06AM |
JH.00003: Magnetometry and Systematic Effects in the Nab Experiment Jason Fry The Nab experiment will determine the electron-neutrino correlation parameter $a$ with a precision of $\delta a / a = 10^{-3}$ and the Fierz interference term $b$ to $\delta b = 3\times10^{-3}$ in unpolarized neutron $\beta$ decay. These results are expected to lead to a new, precise, independent determination of the ratio $\lambda = G_A / G_V$ that will sensitively test CKM unitarity. A long asymmetric spectrometer is optimized to achieve fast proton momentum longitudinalization and the required narrow proton momentum response function. In the Nab spectrometer, a reliable relation of the measured proton TOF to $a$ requires detailed knowledge of the effective proton pathlength, which in turn imposes further requirements on the precision of the magnetic fields in the Nab spectrometer. The Nab magnetometry goals, procedures, and associated systematics will be discussed. [Preview Abstract] |
Saturday, October 15, 2016 11:06AM - 11:18AM |
JH.00004: The Nab/UCNB detection system for electron-proton coincidences in neutron decay Leah Broussard Angular correlations in neutron decay can be used in precise tests of the Standard Model and the search for new physics Beyond the Standard Model. The Nab experiment at the Spallation Neutron Source will determine the electron-neutrino correlation $a$ and the Fierz interference term $b$. The UCNB experiment at the Los Alamos Neutron Science Center will measure the neutrino asymmetry $B$. Thin deadlayer, thick, highly segmented silicon detectors are used to detect the electrons and protons in coincidence in both experiments. A 24 channel prototype detection system based on these silicon detectors has been developed which meets experimental requirements of $\sim$3~keV FWHM energy resolution, rise times of $\sim$50~ns, and energy thresholds below 10~keV. An overview of the requirements on the detection system for precision correlation measurements, results from characterization of the prototype system, and an update on development of the fully instrumented detection system will be presented. [Preview Abstract] |
Saturday, October 15, 2016 11:18AM - 11:30AM |
JH.00005: Update on PEN: A Precise Measurement of the $\pi^+\to e^+\nu(\gamma)$ Decay Emil Frlez The PEN experiment acquired an ensemble of $2.1\cdot 10^7$ $\pi^+$ and $2.8\cdot 10^8$ $\mu^+$ decays at rest during 2008--2010 data collection at the Paul Scherrer Institute, Switzerland. The PEN detector comprises a non-magnetic $3\pi$ solid-angle pure 240-module CsI calorimeter, supplemented with mini-TPC beam particle tracking, beam degrader and active target counters, 20-stave segmented plastic hodoscope and two concentric MWPCs for charged particle tracking and discrimination. We present an update of the status of the PEN data analysis, and of the associated systematic effects. [Preview Abstract] |
Saturday, October 15, 2016 11:30AM - 11:42AM |
JH.00006: Evaluation of Systematic Effects and Data Acquisition System for CALIOPE, an Experimental Search for CP Violation in ortho-Positronium Decays Chelsea Bartram, Reyco Henning, Gulden Othman, Jake Murphy CALIOPE, or CP Aberrant Leptons in o-Ps Experiment, will search for $CP$-violating angular correlations between gamma rays in the decay of positronium. CALIOPE uses a tagged source inserted between two disks of aerogel centered in an annular array of 24 sodium iodide bars. We present an in-depth study of the systematics as well as developments on the DAQ. Specifically, we will discuss the implications of the results from our detailed Monte Carlo simulation as well as the outcomes of several toy Monte Carlo models. We will also present the DAQ design and results from early tests to characterize the position and energy reconstruction of the array. [Preview Abstract] |
Saturday, October 15, 2016 11:42AM - 11:54AM |
JH.00007: Precise Measurement of the Positron Asymmetry in the Decay of Spin-polarized $^{37}$K Benjamin Fenker, Dan Melconian, Spencer Behling, Michael Mehlman, John Behr, Ioana Craiciu, Alexandre Gorelov, James McNeil, Scott Smale, Claire Warner, Melissa Anholm, Gerald Gwinner, Daniel Ashery, Iuliana Cohen Precise low-energy measurements in nuclear $\beta$-decay provide constraints on possible physics beyond the standard model complementary to high-energy collider experiments. We report the most precise measurement of the positron asymmetry from a polarized nucleus to-date. At the TRIUMF Neutral Atom Trap, atoms of the positron emitter $^{37}$K are confined in an alternating-current magneto-optical trap and spin-polarized to $99.13\pm0.09\%$ via optical pumping. The use of atom-trapping techniques allows for an exceptionally open geometry with the decay products escaping the trapping region unperturbed by the trapping potential. We detect the emitted positrons in a pair of symmetric detectors placed along the polarization axis to measure the asymmetry \emph{in situ}. The analysis was performed blind and considers $\beta$-scattering and other systematic effects. The results place limits on the mass of a hypothetical $W$ boson coupling to right-handed neutrinos as well as contribute to an independent determination of the $V_{ud}$ element of the CKM matrix. [Preview Abstract] |
Saturday, October 15, 2016 11:54AM - 12:06PM |
JH.00008: Search for New Physics with Experiment E36 at J-PARC Dongwi H Dongwi We are potentially standing at the precipice in searching for New Physics (NP) beyond the Standard Model (SM) by performing a precision test of lepton universality - a basic assumption of the SM that assigns an identical coupling constant to $e$, $\mu$ and $\tau$. Experiment E36 conducted at J-PARC in Japan will test lepton universality in the $R_{K} = \Gamma(K_{e2})/\Gamma(K_{\mu2})$ ratio. The SM prediction of leptonic $K^{+}$ decays is highly precise with an uncertainty of $\bigtriangleup R_{K} /R_{K} = 4\cdot10^{-4}$. Any observed deviation from the SM prediction would break the universality of the lepton couplings and provide clear indication of NP beyond the SM. Although a successful description of the basic building blocks of matter, the SM is incomplete, falling short to describe dark matter, baryogenesis, neutrino masses and much more. The E36 detector apparatus allows sensitivity to search for light $U(1)$ gauge bosons and sterile neutrinos, which could be associated with dark matter or explain established muon-related anomalies such as the muon g-2 value, and perhaps the proton radius puzzle. A scintillating fiber target was used to stop $K^+$ beam. The $K^+$ products were detected with large-acceptance toroidal spectrometer. Status of data analysis will be presented. [Preview Abstract] |
Saturday, October 15, 2016 12:06PM - 12:18PM |
JH.00009: Measuring branching fractions for $\Lambda \rightarrow p \ell^- \bar{\nu}$ using CLAS at Jefferson Lab Michael McCracken, Reinhard Schumacher Semi-leptonic decays (SLD) of hadrons such as those of the hyperons $Y \rightarrow p \ell^- \bar{\nu}$, provide a testing ground for deviations from Standard Model (SM) predictions in which lepton flavor universality (LFU) is presumed. Such decays have been studied since the late 1960s, yet some channels are poorly constrained; {\em e.g.}, the world dataset for $\Lambda \rightarrow p \mu^- \bar{\nu}$ comprises only 28 events. We present the status of a measurement of the branching fractions for the muonic and electronic decays of the $\Lambda$ using the CLAS detector at Jefferson Laboratory. The dataset contains $1.861\times 10^6$ fully reconstructed $\gamma p \rightarrow K^+ \Lambda$ events in which the $\Lambda$ decays via the dominant hadronic mode ($\Lambda \rightarrow p \pi^-$). Identification of SLD events is complicated by two factors: by the missing momentum carried by the neutrino, and by hadronic decay events in which the pion decays via $\pi^- \rightarrow \mu^- \bar{nu}$ near the $\Lambda$ decay vertex. We demonstrate that a boosted decision tree analysis based on kinematic and vertexing information is sufficient to separate the SLD events from the dominant backgrounds, and thus decrease experimental uncertainties on the branching fraction for the muonic decay. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700