Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session LL: BSM Searches in Fundamental Symmetries VII: Neutrons |
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Chair: Christopher Haddock, NIST Room: Georgian |
Wednesday, October 13, 2021 2:00PM - 2:36PM |
LL.00001: Searching for New Physics and Determining the Neutron Charge Radius with Precision Pendellösung Interference Measurements Invited Speaker: Benjamin Heacock The Bragg-diffracted intensity of a neutron beam incident on a nearly-perfect crystal slab exhibits pendellösung oscillations, the absolute phase of which depends on the neutron wavelength, crystal thickness, and neutron-crystalline potential. Pendellösung interference studies were used to determine the thermally-averaged coherent scattering amplitudes for the (111), (220), and (400) symmetry planes in silicon with relative precision of 5 x 10-5. Fitting the scattering amplitudes to a known functional form results in sensitive measures of silicon’s mean square atomic thermal displacement and the neutron charge radius. When combined with prior determinations of these parameters, constraints on a BSM Yukawa modification to gravity are improved over the 10 nm to 20 pm length scale range. |
Wednesday, October 13, 2021 2:36PM - 2:48PM |
LL.00002: Measuring Higher-Order Neutron-Silicon Structure Factors with Pendellösung Interferometry Robert Valdillez, Takuhiro FUJIIE, Robert W Haun, Benjamin Heacock, Colin A Heikes, Albert Henins, Katsuya Hirota, Shannon M Hoogerheide, Takuya Hosobata, Michael G Huber, Masaaki Kitaguchi, Dmitry Pushin, Hirohiko Shimizu, Masahiro Takeda, Yutaka Yamagata, Albert Young Dynamical diffraction gives rise to multiple waves inside perfect crystals when the incident wave nearly satisfies a Bragg scattering condition. The interference of these waves, called Pendellosung, is observed by "fringe-like" modulation of the intensity of the transmitted or diffracted beams exiting the crystal. Pendellösung interferometry can be used to precisely determine the neutron-silicon structure factor. Structure factors for several different Bragg conditions provide strong constraints for interactions Beyond the Standard Model of particle physics, measure the internal structure of the neutron via the neutron charge radius, and provide information on thermal motion of the atoms in a lattice; aka the Debye-Waller factor. Measuring higher-order structure factors allows for the study of anharmonic contributions, increases the precision of the determined neutron charge radius, and can provide further constraints on an atomic length scale "fifth" force. |
Wednesday, October 13, 2021 2:48PM - 3:00PM |
LL.00003: Improving Neutron Pendell\"{o}sung Interferometry for the Fifth Force Constraints with Germanium Takuhiro FUJIIE, Robert W Haun, Benjamin Heacock, Albert Henins, Katsuya Hirota, Takuya Hosobata, Michael G Huber, Masaaki Kitaguchi, Dmitry Pushin, Hirohiko Shimizu, Masahiro Takeda, Robert Valdillez, Yutaka Yamagata, Albert Young The standard model of particles physics cannot explain the origin of the accelerating expansion of the universe or the hierarchy problem of gravity. Theories beyond standard model of physics created to solve these problems often also predict the existence of a fifth fundamental force. We search for the existence of a fifth force using neutron pendell\"{o}sung interference, where the neutron intensity diffracted from a nearly-perfect crystal oscillates as a function of neutron wavelength, crystal thickness, and neutron material structure factors. Recent experiments have produced precise measurements of the neutron structure factors for the (111), (220), and (400) Bragg reflections in silicon. These data update the limits on the strength of a fifth force on the atomic length scale and include new measurements of the neutron mean square charge radius and silicon Debye-Waller factor. Extension of this experiment to germanium or other crystals will measure the material-specific Debye-Waller factors and increase our sensitivity to the neutron charge radius and fifth forces. In this talk, I report the current status of the neutron structure factor measurements using germanium. |
Wednesday, October 13, 2021 3:00PM - 3:12PM |
LL.00004: A Search for Lorentz-Violating Spin-Gravity Couplings Using Polarized Neutron Interferometry Kyle E Steffen In 1975 Collela, Overhauser, and Werner demonstrated the accessibility of gravitationally-induced phase shifts in quantum systems using perfect silicon crystal neutron interferometry [1]. Measurement of this effect has been made using the OffSpec instrument (ISIS-RAL) in spin-echo mode to act as a polarized neutron interferometer [2] and has recently resulted in the publication of constraints on exotic Z' boson couplings [3]. New theoretical work describing Lorentz-symmetry violation in the spin-dependent matter-gravity sector of the Standard Model Extension (SME) [4] provides the opportunity to search for new interactions through time-series analysis of previously collected data. An overview of the experimental technique will be presented within the context of the SME.
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Wednesday, October 13, 2021 3:12PM - 3:24PM |
LL.00005: A Search for Light Z′ Boson Exchange Using Neutron Spin Rotation Krystyna Lopez An exotic axial vector interaction mediated via exchange of a light Z′ boson can appear in some extensions of the Standard Model [1]. A neutron spin rotation experiment searching for an exotic interaction from this exchange of the form V5 = (gA2/4πm)(e-m0r/r)(1/r + 1/λc)σ→ · (v→ × r→) in the mm-μm range was performed at the LANSCE FP-12 beamline using polarized slow neutrons passing through a target of parallel slotted glass and copper plates [2,3]. We describe the status of an upgraded experiment which can improve on the sensitivity of φ′ = [2.8 ± 4.6(stat.) ± 4.0(sys.)] × 10−5 rad/m achieved in [3] by at least two orders of magnitude at the NIST NG-C beamline. We will also compare our existing and projected sensitivity to the recent claim of an observation of Z′ boson exchange using polarized electrons in NV centers in diamond [4]. |
Wednesday, October 13, 2021 3:24PM - 3:36PM |
LL.00006: New Limits on Mirror Neutron Oscillations Michael Kline, Leah J Broussard It was proposed that the oscillation of neutrons into mirror neutrons, a theoretical dark, sterile counterpart to neutrons, could account for the anomalous discrepancy in beam and bottle measurements of the neutron lifetime. The oscillation is amplified when resonance occurs from the compensation of the magnetic field with the mass difference between neutrons and mirror neutrons resulting in a Landau-Zener transition. A new search at the Oak Ridge National Laboratory was performed to indirectly detect mirror neutrons via the disappearance and regeneration of neutrons in a cold neutron beam with a large, spatially varying magnetic field. Simulations were performed to determine the probability of detecting regenerated neutrons for a wide parameter space of interest and were compared with experimentally determined neutron detection rates. We will present the results of the recent experiment with new detection limits and parameter exclusions and implications for neutron lifetime measurements. |
Wednesday, October 13, 2021 3:36PM - 3:48PM |
LL.00007: Decoherence Calculation for Neutron-Antineutron Bilayer Mirror Reflection Shufan Lu, Kylie A Dickerson, William M Snow A sensitive search for free neutron-antineutron oscillations [1] could either discover a \delta B=2 interaction or constrain post-sphaeleron baryogenesis. Neutron mirror reflection from a uniform medium can preserve the oscillations [2]. Using a recent theory [3] for antineutron-nucleus scattering lengths along with a Lindblad-based formalism [4], we present an estimation of decoherence effect in bilayer mirror reflection for neutron-antineutron two state systems. |
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