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 FE: Mini-Symposium: BSM Searches in Fundamental Symmetries III: EDMs |
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Chair: Alexander Saunders, ORNL Room: Park & Scollay |
Tuesday, October 12, 2021 2:00PM - 2:12PM |
FE.00001: Overview of the neutron electric dipole moment experiment at Los Alamos National Laboratory Steven Clayton The standard model of particle physics predicts an exceedingly small value for the electric dipole moment of the neutron (nEDM). However, beyond standard model theories tend to predict larger values of the nEDM, possibly within the reach of upcoming experiments. This talk will present an overview and status of the nEDM experiment under development at the Los Alamos National Laboratory (LANL) ultracold neutron source and targeting a measurement uncertainty of $3\times 10^{-27}$~$e$-cm. The experiment features a double-cell geometry, 199Hg co-magnetometry, external optical magnetometers, precision holding field coil and gradient coils, and a large, state-of-the-art magnetically shielded enclosure. Some of these features will be covered in more detail in other talks or posters at this conference, with this talk providing a broader view of the experiment. |
Tuesday, October 12, 2021 2:12PM - 2:24PM |
FE.00002: LANL nEDM half scale B0 prototype design and test of the field gradient inside a MSR at LANL Piya A Palamure The measurement of the electric dipole moment of the neutron (nEDM) plays a significant role in finding sources of beyond standard model CP violating physics. The goal of the LANL nEDM experiment is to push the upper limit of the nEDM < 3×10-27 e·cm (68 % CL). A highly uniform magnetic field is key to achieving this substantially high sensitivity for the nEDM measurement by reducing the systematic uncertainties associated with the magnetic field non uniformity. The B0 coil provides the required field uniformity of < 0.3 nT·m-1 at a nominal holding field of 1 µT. This talk will discuss a novel technique employed in the construction of the half scale B0 prototype and the resulting field maps obtained with a half-scale prototype coil housed in a magnetically shielded room (MSR). |
Tuesday, October 12, 2021 2:24PM - 2:36PM Not Participating |
FE.00003: Construction and Performance of the Magnetically Shielded Room for the Neutron Electric Dipole Moment Experiment at Los Alamos National Laboratory Joshua F Burdine A non-zero neutron electric dipole moment (nEDM) demonstrates a CP violation, which is needed to explain the Baryon Asymmetry of the Universe (BAU). Room-temperature nEDM searches using Nuclear Magnetic Resonance (NMR) are leading the forefront of such methodology, as they can get running faster than their cryogenic sister experiments and provide a R&D platform for developing techniques to improve sensitivities. The nEDM search at Los Alamos National Laboratory (LANL) plans to achieve an improved nEDM sensitivity of 3×10-27 e·cm. The experiment requires sophisticated Magnetically Shielded Rooms (MSRs) to shield the experiment apparatus from fluctuations of ambient magnetic fields from DC to high frequency excitations. To achieve the desired sensitivity, we require an ambient gradient smaller than 0.3 nT·m-1. In this talk, I will describe why such experiments require low ambient magnetic fields, how the design characteristics of an MSR affect its shielding factor, the construction of the LANL nEDM MSR (to be completed October 2021), and present results of performance measurement. |
Tuesday, October 12, 2021 2:36PM - 2:48PM |
FE.00004: Magnetic Gradient Coil Design and Validation for the LANL nEDM Experiment Austin R Reid A permanent neutron Electric Dipole Moment (nEDM) presents an experimentally accessible probe for physics beyond the Standard Model. The nEDM@LANL collaboration is constructing a double-cell room-temperature nEDM experiment that aims to use the improved ultracold neutron source, Hg co-magnetometry, magnetic shielding, and magnetic field generation to yield a five-fold improvement in uncertainty to 3×1027 e·cm. |
Tuesday, October 12, 2021 2:48PM - 3:00PM |
FE.00005: Design of the Holding Field and Spin-Transport Coil System for the LANL nEDM Experiment Jared Brewington Permanent electric dipole moments present a promising avenue for the discovery of beyond standard model physics. The advent of experimental techniques using stored ultracold neutrons (UCNs) has placed the neutron electric dipole moment (nEDM) at the forefront of permanent electric dipole moment searches. The current experimental upper limit for the nEDM is $d_n < 1.8\times10^{-26}$ e-cm (90\% CL). The neutron EDM search to be conducted at Los Alamos National Laboratory (LANL) aims to advance the experimental measurement of the nEDM to an uncertainty of $3\times10^{-27} $ e-cm (68\% CL). Reaching the proposed uncertainty requires precise magnetic field control, specifically a highly uniform $B_0$ holding field. In the LANL-nEDM experiment, the holding field is provided by a gapped solenoid with an octagonal cross section. Efficient transport of UCN polarization from the polarizing magnet into the storage volume is also essential to accomplish the goal uncertainty. A series of modified, self-shielding cos $\theta$ coils have been designed to meet the specification for polarization transport. The two coil systems interface in a pseudo-continuous manner such that the fringe fields do not depolarize the UCNs during transport or generate non-uniformities in the cell volumes. This talk will discuss the techniques employed in the design of the $B_0$ and spin-transport coils for the LANL-nEDM experiment. |
Tuesday, October 12, 2021 3:00PM - 3:12PM |
FE.00006: Magnetic Field Approximation with Radial Basis Function Interpolation for the LANL nEDM Experiment Felicity Hills, Timothy E Chupp The Los Alamos neutron EDM experiment aims to measure the neutron’s electric dipole moment with a uncertainty of 3 × 10−27 e·m in a double ultracold neutron storage cell apparatus. To reach this target, we require magnetic effective field stability of < 150 fT over 500 s, accomplished with a combination of magnetic shielding and magnetometry. The experiment will use an array of external scalar magnetometers with optically pumped magnetometers (OPMs) as well as potential 199Hg comagnetometers. Since scalar magnetometers and the neutron spins measure only the field magnitude, we can approximate the magnitude of the field averaged over the storage cells using interpolation techniques. Radial Basis Function (RBF) interpolation is well-suited for interpolation problems with sparse, irregularly spaced (meshless) measurement nodes. An RBF φ(r) must be positive definite and depends only on the radial distance from each measurement node. The interpolation algorithm optimizes over a linear combination of the RBFs from each node. In simulations of a magnetic field with 10 pT variations across the two cells, the RBF interpolation with stable magnetometers at 35 measurement nodes recovered the change of the field to ∼10 fT. Ongoing work has the goal to reach the sensitivity goal or better with a reduced number of magnetometers. |
Tuesday, October 12, 2021 3:12PM - 3:24PM |
FE.00007: Search for Lorentz violation using experiments measuring neutron electric dipole moment Prajwal T MohanMurthy, Jeff A Winger Lorentz symmetry is a cornerstone of both general relativity (GR) and the standard model (SM). It ensures that the physical laws are invariant under rotations and boosts. Both GR and the SM are considered to be low energy limits of a more fundamental theory at the Plank scale. Many such theories at the Plank scale spontaneously violate the Lorentz symmetry, even though no such violation has ever been experimentally verified. However, violations of Lorentz symmetry have already been incorporated into an effective field theory known as the standard model extension. Measurement of a statistically significant cosmic anisotropic field such as a: magnetic field, $\tilde{b}$, magnetic moment, $\mu_{ij}$, or an electric dipole moment, $d_{ij}$, are all indications for the violation of Lorentz symmetry. |
Tuesday, October 12, 2021 3:24PM - 3:36PM |
FE.00008: Study of the Behavior of Ions on Plastic Surfaces in Cryogenic Liquids. Ashok Timsina, Mark A Broering, Wolfgang Korsch In the nEDM@SNS experiment, a cryogenic apparatus will be used to improve the present limit on the neutron electric dipole moment(nEDM) by about two orders of magnitude with an ultimate sensitivity of ∼3x10-28e-cm. In this apparatus, two PMMA cells will be filled with superfluid He-4 which can support strong electric fields. High voltage electrodes are placed outside of the measurement cells to generate a strong and stable electric field (∼75 kV/cm). During the experiment, however, ambient ionization radiation can ionize helium. These ionized charges (He ions and electrons) are bound on the cell’s walls. As a result, an opposing static electric field is generated, which will impact the stability of the electric field. This change in E-fields directly influences the desired sensitivity measurement in the measurement of the nEDM. Therefore, a compact test setup has been devised to study the behavior of ions inside cryogenic liquids using a scaled-down version of the nEDM cell and the electrodes. In our setup, ions are generated by ionizing the helium(nitrogen) with a 137Cs source and the electric field is monitored via the electro-optical Kerr effect. We plan to develop a new method to measure the minimum energy required to remove the ions from the surface of the measuring cells and study the effect of fringe fields. Dependent on the results, we might neutralize the charge preferably by reversing the electric field direction to guarantee the required stability of the E-fields. This talk will present the experimental design and first results of measuring the binding energy of nitrogen ions on the PMMA surface inside the liquid nitrogen. |
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