Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session T11: Neutron PhysicsLive
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Sponsoring Units: DNP Chair: Francisco Gonzalez, Indiana University |
Monday, April 19, 2021 3:45PM - 3:57PM Live |
T11.00001: Pendell\"{o}sung Interferometry Measures the Neutron Charge Radius and Constrains New Physics Benjamin Heacock, Takuhiro Fujiie, Robert Haun, Albert Henins, Katsuya Hirota, Takuya Hosobata, Michael Huber, Masaaki Kitaguchi, Dmitry Pushin, Hirohiko Shimizu, Masahiro Takeda, Robert Valdillez, Yutaka Yamagata, Albert Young We use neutron pendell\”{o}sung interferometry to measure the thermally-averaged, single-atom coherent elastic scattering amplitudes for the (111), (220), and (400) Bragg reflections in silicon. The data is used to make the first competitive neutron scattering determination of the neutron mean-square charge radius in over twenty years with experimental systematics which are notably different from prior measurements. Additionally, the tabulated scattering amplitudes are used to constrain a Yukawa-modification to gravity over the 20 pm to 10 nm length scale range. [Preview Abstract] |
Monday, April 19, 2021 3:57PM - 4:09PM Live |
T11.00002: Universal Decoherence Calculation for Neutron-Antineutron Mirror Reflection Shufan Lu, Kylie Aurora Dickerson, William Michael Snow Recent calculations of the mirror reflection of an oscillating neutron-antineutron system [1] uncovered a regime of high reflectivity in the limit of small reflection angles. We present an analysis of the effect of neutron decoherence in mirror reflection in the presence of both absorption and scattering for mirrors composed of stable nuclei. We use Kerbikov's Lindblad-based formalism [2] along with the residence time of the neutrons and antineutrons in the mirror as derived from neutron optics [3] and confirmed in the recent measurement of the neutron Goos-Hänchen effect [4] and a recent analysis of antineutron-nucleus scattering lengths [5]. //// [1] V. V. Nesvizhevsky, V. Gudkov, K. V. Protasov, W. M. Snow, and A. Yu. Voronin, Phys. Rev. Lett. 122, 221802 (2019). arXiv: 1810.04988. [2] B. O. Kerbikov, Phys. Lett. B 795 (2019) 362. arXiv:1810.02153. [3] A I Frank, J. Phys.: Conf. Ser. 528 012029 (2014). [4] V. -O. de Haan, J. Plomp, T. M. Rekveldt, et al., Phys. Rev. Lett. 104 010401 (2010). [5] K. V. Protasov, V. Gudkov, E. A. Kupriyanova, V. V. Nesvizhevsky, W. M. Snow, and A. Yu. Voronin, Phys. Rev. D 102, 075025 (2020). arXiv: 2009.11467. [Preview Abstract] |
Monday, April 19, 2021 4:09PM - 4:21PM Live |
T11.00003: A Uniform Magnetic Coil for Sterile Neutron Oscillation Searches Zach Mistelske A possible solution to the mystery of dark matter, the neutron lifetime anomaly, and the baryon asymmetry of universe could be neutrons oscillating into sterile ‘mirror’ neutrons through a dark sector, only interacting with particles of our ordinary (Standard Model) sector through gravity and some potentially exotic interactions. Such oscillations would only occur under specific conditions, such as within a magnetic field, thus compensating the energy level suppression, and thus allowing both neutrons and mirror neutrons achieve identical energy states. These oscillations could be observed by detecting beam losses as neutrons pass through a thick absorber within particular magnetic field configurations. I will describe a magnetic coil made to create the required uniform ~|10|G field in any direction for the neutron oscillation, and compact enough to fit within the 1 m long sections of upstream collimators of the ORNL HFIR GP-SANS instrument General Purpose-Small Angle Neutron Scattering beamline at Oak Ridge National Laboratory, where a search is planned. The coil consists of two double-cos(theta) coils and a solenoid covered by a sheet of mu-metal which keeps the inner uniform magnetic fields shielded from any external magnetic fields. [Preview Abstract] |
Monday, April 19, 2021 4:21PM - 4:33PM Live |
T11.00004: A Tunable Sheared Elliptical Solenoid for Precision Neutron Beam Experiments David Bowles Because of~?the~neutron's neutrality, many fundamental symmetries experiments instead exploit its magnetic moment and use~precise magnetic fields to manipulate neutron beams. One implementation requirement of experimental searches for beyond Standard Model sterile (mirror) neutron oscillations is a \textasciitilde \textbar 10\textbar G magnetic field, tunable to arbitrary directions, and maintaining a uniformity to \textasciitilde \textbar 2\textbar mG.~ I will present a symmetric design involving a series of three sheared elliptical solenoids layered and rotated by 2$\pi $/3 with respect to each other, which can produce both uniform solenoidal and transverse magnetic fields.~ The three coils can be tuned not only to produce an arbitrary field in any direction, but also to~actively compensate for small variations in background fields along the beam axis. These nonstandard wire geometries have been fully realized using 3D printing technology. [Preview Abstract] |
Monday, April 19, 2021 4:33PM - 4:45PM Live |
T11.00005: Pulse Shape Discrimination for the Nab Experiment David Mathews, Leah Broussard The Nab neutron beta decay correlation experiment will measure the parameter “a”, the electron-neutrino correlation coefficient, and “b”, the Fierz interference term. “a” can be directly mapped to the unitarity of the CKM matrix while “b” places limits on the presence of new physics via scalar or tensor couplings in the weak interaction. These coefficients will be determined through measurements of coincident protons and electrons with a pair of pixelated silicon detectors. The signals created by the incident particles vary in shape depending on multiple parameters such as energy and hit location. To reach the precision goals of the experiment, the mean timing bias must be <1ns with an energy resolution better than 3keV. A new signal analysis methodology has been developed that utilizes Nvidia GPUs to fit template waveform shapes. This technique is capable of pulse shape discrimination in real-time and can be used to address sources of bias originating from variations in charge deposition. [Preview Abstract] |
Monday, April 19, 2021 4:45PM - 4:57PM Live |
T11.00006: Revisiting the measurement of neutron lifetime using storage bottles Prajwal MohanMurthy Neutron lifetime is a critical parameter in the Standard Model. Its measurements using various techniques reveals serious tension. When ultracold neutrons are stored in material bottles, they can be lost to various processes: $\beta-$decay, absorption, and most important up-scattering on material walls. In the past, lifetime extraction by performing a disappearance measurement in material storage bottles, isolated the wall scattering losses, by comparing the decay curves from at least two storage chambers, with varying volume to surface-area ratios. This technique has been superseded by measurements performed with magneto-gravitational traps which avoids the wall scattering losses altogether. However, here we revisit the lifetime measurement in material storage bottle dominated by losses from wall scattering. Information about the neutron energy spectra, coupled with well characterized scattering loss coefficient of the wall materials, can be used to analyze neutron decay curve measured in a single storage chamber to extract neutron lifetime. Sensitivity of such an analysis, using the best available estimates of the energy spectra and scattering loss coefficients, upon the neutron lifetime will be discussed. [Preview Abstract] |
Monday, April 19, 2021 4:57PM - 5:09PM Live |
T11.00007: Novel Cross Section Measurements through Absolute High-Precision Cold Neutron Fluence Determination Hans Mumm, E. Adamek, J. Caylor, M. Dewey, C. Haddock, D. Gilliam, E. Pirovano, E. Scott The National Institute of Standards and Technology has developed an instrument (Alpha-Gamma) that utilizes the interaction of neutrons with a totally absorbing 10B target to precisely measure the flux of a well-collimated monochromatic neutron beam. This measurement provides a calibration of the 6Li (n,alpha) 3H based flux monitor used in the NIST beam-based neutron lifetime experiment to better than 0.1 {\%} and is now being utilized in novel, 0.2 {\%} level, measurements of the 235U neutron-induced fission and 6Li cross sections.~ These ancillary measurements will provide systematically independent determinations of these important quantities. The results of recent and ongoing measurements will be presented, and planned operations will be discussed. [Preview Abstract] |
Monday, April 19, 2021 5:09PM - 5:21PM Live |
T11.00008: BL3: Next generation beam experiment to measure the neutron lifetime Nadia Fomin Neutron beta decay is an archetype for all semi-leptonic charged-current weak processes. A precise value for the neutron lifetime is required for consistency tests of the Standard Model and is needed to predict the primordial 4He abundance from the theory of Big Bang Nucleosynthesis. An effort is under way for an in-beam measurement of the neutron lifetime that is able to evaluate the systematic uncertainties at the 0.3 s level. This effort is part of a phased campaign of neutron lifetime measurements based at the NIST Center for Neutron Research, using the Sussex-ILL-NIST technique. Recent advances in neutron fluence measurement techniques as well as new large area silicon detector technology address the two largest sources of uncertainty for in-beam measurements, paving the way for a new measurement. The experimental design, schedule, and projected uncertainties for the main subsystems will be discussed. [Preview Abstract] |
Monday, April 19, 2021 5:21PM - 5:33PM Live |
T11.00009: Geometric Optimization of a Symmetric System of Neutron Flux Detectors for BL3 Austin Nelsen, Emily Ballantyne, Rebecca Calvert, Sarah Vickers, Chris Crawford The recent measurement of the lifetime of the free neutron using the beam method has an 8.7 s (4$\sigma$) discrepancy with UCN measurements. The goal of the BL3 experiment is to improve the statistical error of this measurement and explore systematic uncertainties as an explanation for the discrepancy. A well-characterized neutron flux detector with flat response is important since the neutron flux enters linearly into the neutron lifetime. I will present a group theoretic formalism for the geometric optimization of $n$ neutron detectors for uniform acceptance as a function of the neutron position and describe how to use this symmetry to extract other parameters from the detector rates such as the beam centroid, ellipticity, and RMS width. [Preview Abstract] |
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