Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session SG: Mini-Symposium: Precision Beta Decay V |
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Chair: Christopher Swank, Caltech |
Sunday, November 1, 2020 10:30AM - 11:06AM |
SG.00001: Next generation neutron beta decay correlation experiments Invited Speaker: Steven Clayton Neutron beta decay, in which a neutron decays into a proton, electron, and antineutrino, presents a number of observables which can be used to test the Standard Model. The correlations between decay product momenta with neutron spin or each other are sensitive to a small number of Standard Model parameters, and measurement of these correlations determine the underlying parameters. This talk presents an overview of upcoming experiments to measure neutron beta decay angular correlation parameters, chiefly $A$ and $a$, the correlations between electron momentum and neutron spin, and between the electron and anti-neutron momenta, respectively, each sensitive to the nucleon’s weak-axial charge. Potential sources of systematic errors vary for these experiments, which will provide a check for underestimated systematic uncertainty. The precision goals of these experiments, if achieved, will enable stringent tests for Beyond Standard Model physics at the $\sim$10~TeV level. [Preview Abstract] |
Sunday, November 1, 2020 11:06AM - 11:18AM |
SG.00002: Recent results from the aCORN experiment Md T Hassan Free neutron decay into a proton, electron, and antineutrino is one of the simplest examples of nuclear beta decay. The electron-antineutrino~correlation ($a$-coefficient) is one important experimental observable of neutron decay. Along with other observables such as the neutron lifetime and beta asymmetry, the $a$-coefficient can be used~to determine the charged weak couplings of neutrons and protons, measure the CKM matrix element Vud, and conduct precision low~energy tests of physics beyond the Standard Model. The aCORN experiment uses a novel ``wishbone asymmetry'' method~that does not require detailed proton spectroscopy to measure the neutron~$a$-coefficient. We will present results from the second aCORN run on the high-flux~beamline NG-C at the NIST Center for Neutron Research. [Preview Abstract] |
Sunday, November 1, 2020 11:18AM - 11:30AM |
SG.00003: Systematic Effects in the aCORN Experiment Fred Wietfeldt The aCORN experiment measures the neutron decay $a$-coefficient. Important systematic effects from the aCORN NG-C run will be discussed. These include transverse magnetic and electric fields, electron backscatter, proton scattering and focusing, collimator alignment, residual gas interactions, and neutron polarization. [Preview Abstract] |
Sunday, November 1, 2020 11:30AM - 11:42AM |
SG.00004: An Overview of the Nab Experiment and the Results from Magnetic Field Mapping Elizabeth Scott The Nab experiment aims to measure the neutron beta decay electron-neutrino correlation coefficient "a" and the Fierz interference term "b". Measurement of "a" to a relative uncertainty of $10^{-3}$ provides a determination of $ \lambda$, the ratio of axial to vector coupling constant, at roughly the same precision level as the vector coupling determined from the superallowed decays. A measurement of "b" with an uncertainty of $3 \times 10^{-3}$ would provide a sensitive test of physics beyond the Standard Model. In Nab, the parameter "a" is extracted from the electron energy and proton time of flight (TOF) using an asymmetric magnetic spectrometer and two large-area highly pixelated Si detectors. To reach the goal of $10^{-3}$ relative uncertainty in "a", Nab requires understanding of its possible systematic effects via a detailed mapping and analytic expansion of the magnetic field. My talk focuses on the results of the initial mapping and the suggested path forward. [Preview Abstract] |
Sunday, November 1, 2020 11:42AM - 11:54AM |
SG.00005: Preliminary Characterization of Silicon Detectors for the Neutron Beta Decay Experiment (Nab) using the Manitoba II 30 keV Proton Source Nicholas Macsai Neutron beta decay is a fundamental nuclear process that provides a means to perform precision measurements that test the limits of our present understanding of the weak interaction described by the Standard Model of particle physics and puts constraints on physics beyond the Standard Model. The Nab experiment will measure $a$, the electron-neutrino angular correlation parameter and $b$, the Fierz interference term. The Nab experiment implements large area segmented silicon detectors to detect proton momentum and electron energy to determine $a$ to a precision of $\delta a / a \sim 10^{-3}$ and $b$ to a precision of $\delta b = 3 \cdot 10^{-3}$. The Nab silicon detectors are being characterized by protons prior the execution of Nab experiment. This talk will present preliminary measurements on the electronic response of detector pixels. [Preview Abstract] |
Sunday, November 1, 2020 11:54AM - 12:06PM |
SG.00006: An Overview of the Nab Data Acquisition and Real Time Waveform Analysis System David Mathews The Nab neutron decay correlation experiment will measure the electron-neutrino correlation coefficient “a” and by extension unitarity of the CKM matrix. This coefficient will be determined through a measurement of the 2D energy spectrum of coincident protons and electrons on a pair of 127 pixel silicon detectors. The signals created by particles interacting with each pixel will be processed in FPGA on National Instrument digitizers using newly developed filtering techniques that allow for real-time fitting of pulse-shape parameters for extraction of both energy and timing. After initial processing on the FPGAs, relevant signals will be sent to Nvidia GPUs for higher precision energy and timing with lossless compression for long-term storage. An overview of the DAQ system design and algorithms will be presented. [Preview Abstract] |
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