Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session D07: Neutron Physics |
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Sponsoring Units: DNP Chair: Maninder Singh, Los Alamos National Lab Room: MG Salon G - 3rd Floor |
Saturday, April 15, 2023 3:45PM - 3:57PM |
D07.00001: Measurement of Compensated Ferrimagnetism in Terbium Iron Garnet using Neutron Spin Echo Spectroscopy Caleb D Hughes, David Baxter, Matthew Frost, Lilian M Lommel, Joshua C Long, Thomas Mulkey, Mary Odom, William M Snow, Piotr A Zolnierczuk Rare-earth iron garnets constitute a model system for Néel ferrimagnetism. These materials exhibit temperature-dependent orbital cancellation of the magnetism associated with the electron spins, leaving a dense ensemble of polarized electrons which are of interest as a source for exotic spin-dependent fifth-force searches. We have conducted the first neutron spin echo investigation of the ferrimagnetic state of a terbium iron garnet (Tb3Fe5O12) sample. In contrast to measurements of external fields, neutrons can probe the internal state of the ferrimagnet and determine if the cancellation of moments occurs at the unit cell level or is an emergent property as a result of compensation among inhomogeneously-distributed domains. We describe the sample characterization, the apparatus used, as well as preliminary results. |
Saturday, April 15, 2023 3:57PM - 4:09PM |
D07.00002: Measurement for Spin-Dependent Fifth Force in Terbium Iron Garnet using Neutron Spin Echo Spectroscopy Thomas Mulkey, David Baxter, Matthew Frost, Caleb D Hughes, Lilian M Lommel, Joshua C Long, Mary Odom, William M Snow, Piotr A Zolnierczuk It is well known that some rare-earth iron garnets exhibit temperature dependent orbital cancellation of the magnetism associated with the electron spins while possessing non-zero net electron spin. This provides an opportunity to search for exotic spin-dependent interactions in beyond-the-Standard Model physics via spin-polarized samples with minimal magnetic background. We will discuss the results of a novel neutron-electron interaction search in the rare earth iron garnet Tb3Fe5O12 conducted at the Spallation Neutron Source using the Neutron Spin Echo beamline at Oak Ridge National Laboratory. |
Saturday, April 15, 2023 4:09PM - 4:21PM |
D07.00003: Performing an accurate measurement of Δb_i of 3He using Neutron Spin Echo Earl Babcock, William M Snow, Boyd M Goodson, Hao Lu, Sepehr Samiei
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Saturday, April 15, 2023 4:21PM - 4:33PM |
D07.00004: Progress on Precision Cross Section Measurements with the NIST Alpha-Gamma Device Hans P Mumm, Evan R Adamek, Jimmy Caylor, Maynard Dewey, Richard Essex, Elisa Pirovano, Elizabeth M Scott, Mark Tyra The Alpha-Gamma device at the National Institute of Standards and Technology utilizes the interaction of neutrons with a totally absorbing $^{10}$B target to precisely measure the flux of a monochromatic neutron beam. This measurement provides a calibration of the $^{6}$Li(n,$alpha$)$^{3}$H based flux monitor used in the NIST neutron lifetime experiment to better than 0.1,\% and is also being utilized in novel, 0.2,\% level, measurements of the $^{235}$U neutron-induced fission and $^6$Li neutron capture cross sections in an effort to provide systematically independent determinations of these important quantities. Each of these measurements requires ancillary efforts to characterize, for example, device solid angles, target characteristics, and alpha counting efficiencies. The results of recent and ongoing characterization measurements will be presented. |
Saturday, April 15, 2023 4:33PM - 4:45PM |
D07.00005: Updates of the Nab Experiment: A Precise Measurement of Unpolarized Neutron Beta Decay Jason A Fry Neutron beta decay provides sensitive means to uncover the details of the weak interaction by evaluating the ratio of axial-vector to vector coupling constants in the standard model, λ = GA / GV, through multiple decay correlations. The Nab experiment at the SNS in ORNL will make precise measurements of the electron-neutrino correlation parameter a and the Fierz interference term b in unpolarized free neutron beta decay. These results aim to deliver an independent determination of λ that will sensitively test CKM unitarity, as well as probe exotic electroweak scalar and tensor currents. Nab utilizes the world's largest cryogen-free superconducting magnet spectrometer to guide the decay products to two large area silicon detectors in order to precisely determine the electron energy and proton momentum. The Nab apparatus is being commissioned with more data to be taken soon. We will present an overview and updates of the Nab experiment, including a discussion of some systematic studies and effects. |
Saturday, April 15, 2023 4:45PM - 4:57PM |
D07.00006: The TUCAN EDM Experiment Jeffery W Martin The TUCAN (TRIUMF Ultra-Cold Advanced Neutron) collaboration aims to measure the neutron electric dipole moment (EDM) with improved precision. The experiment will use a new high-intensity ultracold neutron (UCN) source currently being constructed at TRIUMF (Canada's Particle Accelerator Centre, Vancouver, BC). Our UCN production scheme is based on spallation neutron production and super-thermal UCN conversion with superfluid helium (He-II), and has been successfully demonstrated by a prototype UCN source operated from 2017-2019 at TRIUMF. With our newly upgraded source, a statistical EDM sensitivity of 10−27 e⋅cm would be achieved in 400 days of data taking. Core components of the new UCN source, such as optimized neutron moderators, a high-performance helium cryostat, and a nickel-plated UCN production vessel have been built and tested, and are being assembled at TRIUMF. The development of components of the neutron EDM spectrometer, such as a magnetically shielded room, atomic magnetometers, UCN polarization analyzers and a UCN precession chamber are advancing in parallel. In this presentation, an overview of the recent progress by the TUCAN collaboration will be presented, and prospects for the new neutron EDM measurement will be discussed. |
Saturday, April 15, 2023 4:57PM - 5:09PM |
D07.00007: Update on the Neutron Decays to Dark Matter via the n→X+γ Branch Jin Ha Choi There is a 4 σ discrepancy between the free neutron lifetime measured via the "beam" method, which probes the p+e+$ar{ν}$ branch, and the "bottle" method, which probes the total decay rate. Theory by Fornal and Grinstein attempted to resolve such discrepancy by hypothesizing a Dark Matter + γ-ray decay branch for a free neutron, where an additional 1% decay branch could explain the discrepancy between two methods. At the Los Alamos UCN Source, during the 2018 beam cycle, a High-Purity Germanium (HPGe) detector was installed next to an ultracold neutron (UCN) buffer volume in the UCNτ beamline to search for a monoenergetic gamma peak associated with the Dark Matter decay mode. The statistical significance of this measurement is influenced by the knowledge of the number of UCN in the buffer volume, since this sets the upper bound on the expected intensity of the monoenergetic gamma peak. In addition to the previously measured UCN density, we have developed a detailed model of UCN transport to place additional constraints on the UCN density distribution in the buffer volume. In this talk, we will present the result of this search incorporating these new simulations to improve on previous null results that have been published and presented. |
Saturday, April 15, 2023 5:09PM - 5:21PM |
D07.00008: Systematic Effects and Detection Efficiencies in the BL2 In-Beam Neutron Lifetime Experiment Shannon F Hoogerheide Neutron beta decay is the simplest example of nuclear beta decay and is important to our understanding of weak processes, the unitarity of the CKM matrix in the Standard Model, Big Bang Nucleosynthesis models, solar physics, and the detection of reactor antineutrinos. The BL2 In-beam neutron lifetime experiment seeks to address a current discrepancy between previous beam-based neutron lifetime experiments and recent ultra-cold neutron bottle neutron lifetime experiments through careful study of possible systematic effects made possible by apparatus upgrades, proton and neutron detection improvements and new analysis techniques. This talk will discuss key systematic effects, including the results of new systematic studies regarding the detection efficiencies of protons and molecular hydrogen. An update on the status and outlook of the BL2 experiment will also be presented. |
Saturday, April 15, 2023 5:21PM - 5:33PM |
D07.00009: Sensitive study of cosmic ray muon flux variations with Earth's atmosphere, solar activity and geomagnetic disturbances Arfa Mubashir, Xiaochun He Driven by the advancements in particle detection technologies, in recent years, there has been a growing interest in using cosmic rays, particularly muon particles, for many practical applications – ranging from tomography to space and earth weather monitoring. The challenge in space and earth weather monitoring on a global scale using cosmic rays is to deploy many efficient and affordable detectors that can provide accurate correlations between cosmic ray flux variations and the weather conditions. |
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