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 1WB: Frontiers in Neutron Physics I |
Hide Abstracts |
Chair: H. Pieter Mumm, NIST |
Thursday, October 29, 2020 9:00AM - 9:36AM |
1WB.00001: Precision neutron scattering lengths using~neutron interferometry Invited Speaker: Michael Huber Historically, neutron interferometry (NI) has been the preferred method for measuring neutron scattering lengths due to its incredible phase sensitivity and negligible systematic effects. Although scattering lengths are widely used in neutron science and nuclear engineering, the scattering lengths of many isotopes are known only to a few percent relative uncertainty. Since 2001, the NI facility at NIST has been engaged in sub 0.1 {\%} measurements of light nuclei that include hydrogen, deuterium, helium-3 and helium-4. A significant motivation for more precise measurements of neutron scattering lengths is to provide high-quality ``set-point'' data for effective range expansions that can be used to assist construction of improved phenomenological nuclear models. Further, they help constrain low-energy constants used in high order nuclear chiral effective field theory calculations. In either case it is hoped that such new models will bring few nucleon theory and experiment into better agreement. A NI spatially separates the wavefunction of a single neutron, via Bragg diffraction, into two spatially separated coherent paths. The relative phase shift between the two paths causes a modulation in the neutron intensity measured after the interferometer. For gaseous samples, an aluminum cell filled with a target gas was placed in one path of the interferometer. The phase shift due to the neutron-gas interaction is proportional to the gas density and scattering length. The gas density was determined from the known temperature and pressure of the sample gas. Our most recent result [Haun et al., PRL \textbf{124} (2020)] for n-$^{\mathrm{4}}$He represented a factor of 10 improvement over previous efforts and a 2 {\%} shift in the world average. Further, the measurement of helium-4 provided insight into systematics not previously considered in weakly scattering gas targets. [Preview Abstract] |
Thursday, October 29, 2020 9:36AM - 10:12AM |
1WB.00002: Hadronic Parity Violation with Cold Neutrons: New Experimental Results and their Implications. Invited Speaker: Michael Gericke The hadronic weak interaction between nucleons remains one of the least well-understood aspects of electro-weak theory. The interaction is generally described in terms of 6 weak meson-nucleon coupling constants or the corresponding low energy constants in modern effective field theories. To make interpretable connections between the measured and calculated observables and constraint the coupling constants one needs a complete set of few-body experiments. To date, there is no complete set of experiments for any of the various theory models, which is mostly a result of the high degree of experimental difficulty. Nor have all of the measured or measurable observables been calculated in each model. The two most recent hadronic weak interaction measurement results from the NPDGamma and n3He parity-violating cold neutron capture experiments have achieved the smallest errors in this field yet and place significant new constraints on the theory. I will discuss the current experimental status and the implications with respect to theory, and briefly list some examples of upcoming and future experimental work. [Preview Abstract] |
Thursday, October 29, 2020 10:12AM - 10:48AM |
1WB.00003: Neutron electric dipole moment searches Invited Speaker: Beatrice Franke Observations show us that our Universe is matter dominated. Key to improving the understanding of this asymmetry between matter and antimatter (also referred to as the Baryon Asymmetry of the Universe BAU) are processes that involve CP-violation -- that is the violation of the combined symmetries of charge conjugation (C) and parity transformation (P). The Standard Model (SM) of Particle Physics fails to explain the observed ratio between matter and antimatter by several orders of magnitude due to a lack of CP-violating processes. Thus, searches for those are very powerful beyond SM physics probes. A permanent non-zero electric dipole moment (EDM) of the free neutron violates P and time reversal (T) symmetry. T-violation is equivalent to the CP-violation, taking the CPT theorem for granted. This constitutes a strong link between the neutron EDM and one of the most pressing questions of contemporary fundamental physics research -- solving the riddle of the BAU. In this presentation I will motivate why searches for a measurable neutron EDM are so impactful and yet so difficult. Subsequently, I will give an overview of the several different efforts around the globe to improve the sensitivity towards this elusive quantity and how the different collaborations tackle the intricacies of this high precision search. [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