Measurement of the Positive Muon Anomalous Magnetic Moment to 0.20 ppm.

We present a new measurement of the positive muon magnetic anomaly, a_{μ}≡(g_{μ}-2)/2, from the Fermilab Muon g-2 Experiment using data collected in 2019 and 2020. We have analyzed more than 4 times the number of positrons from muon decay than in our previous result from 2018 data. The systematic error is reduced by more than a factor of 2 due to better running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, ω[over ˜]_{p}^{'}, and of the anomalous precession frequency corrected for beam dynamics effects, ω_{a}.

Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm.

We present the first results of the Fermilab National Accelerator Laboratory (FNAL) Muon g-2 Experiment for the positive muon magnetic anomaly a_{μ}≡(g_{μ}-2)/2. The anomaly is determined from the precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency ω_{a} between the spin-precession and cyclotron frequencies for polarized muons in a magnetic storage ring.

New Limit on the Permanent Electric Dipole Moment of ^{129}Xe Using ^{3}He Comagnetometry and SQUID Detection.

We report results of a new technique to measure the electric dipole moment of ^{129}Xe with ^{3}He comagnetometry. Both species are polarized using spin-exchange optical pumping, transferred to a measurement cell, and transported into a magnetically shielded room, where SQUID magnetometers detect free precession in applied electric and magnetic fields. The result from a one week measurement campaign in 2017 and a 2.

First Observation of P-odd γ Asymmetry in Polarized Neutron Capture on Hydrogen.

We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=[-3.

Precision Measurement of the Radiative β Decay of the Free Neutron.

The standard model predicts that, in addition to a proton, an electron, and an antineutrino, a continuous spectrum of photons is emitted in the β decay of the free neutron. We report on the RDK II experiment which measured the photon spectrum using two different detector arrays. An annular array of bismuth germanium oxide scintillators detected photons from 14 to 782 keV.

(19)F(α,n) thick target yield from 3.5 to 10.0 MeV.

Using a target of PbF2, the thick-target yield from the (19)F(α,n) reaction was measured from E(α)=3.5-10 MeV. From these results, we infer the thick-target neutron yields from targets of F2 and UF6 over this same alpha-particle energy range.

New limit on time-reversal violation in beta decay.

We report the results of an improved determination of the triple correlation DP·(p(e)×p(v)) that can be used to limit possible time-reversal invariance in the beta decay of polarized neutrons and constrain extensions to the standard model. Our result is D=[-0.96±1.

A microfabricated phantom for quantitative MR perfusion measurements: validation of singular value decomposition deconvolution method.

A perfusion phantom with unique features and a wide variety of applications in MR and other imaging modalities is presented. Using microfabrication technique, a network of microchannels, in the scale of actual microvasculature, was created. The geometry of the network was determined based on Murrays minimum work law to simulate the hemodynamic in actual capillary networks.

Neutron beam effects on spin-exchange-polarized 3He.

We have observed depolarization effects when high intensity cold neutron beams are incident on alkali-metal spin-exchange-polarized 3He cells used as neutron spin filters. This was first observed as a reduction of the maximum attainable 3He polarization and was attributed to a decrease of alkali-metal polarization, which led us to directly measure alkali-metal polarization and spin relaxation over a range of neutron fluxes at Los Alamos Neutron Science Center and Institute Laue-Langevin. The data reveal a new alkali-metal spin-relaxation mechanism that approximately scales as sqrt[phi_{n}], where phi_{n} is the neutron capture-flux density incident on the cell.

Observation of the radiative decay mode of the free neutron.

The theory of quantum electrodynamics (QED) predicts that beta decay of the neutron into a proton, electron and antineutrino should be accompanied by a continuous spectrum of soft photons. While this inner bremsstrahlung branch has been previously measured in nuclear beta and electron capture decay, it has never been observed in free neutron decay. Recently, the photon energy spectrum and branching ratio for neutron radiative decay have been calculated using two approaches: a standard QED framework and heavy baryon chiral perturbation theory (an effective theory of hadrons based on the symmetries of quantum chromodynamics).

Measurement of Neutron Decay Parameters-The abBA Experiment.

We are developing an experiment to measure the correlations a, A, and B, and the Fierz interference term b in neutron decay, with a precision of approximately 10(-4). The experiment uses an electromagnetic spectrometer in combination with two large-area segmented silicon detectors to detect the proton and electron from the decay in coincidence, with 4π acceptance for both particles. For the neutron-polarization-dependent observables A and B, precision neutron polarimetry is achieved through the combination of a pulsed neutron beam, under construction at the SNS, and a polarized (3)He neutron polarizer.

Commissioning of the NPDGamma Detector Array: Counting Statistics in Current Mode Operation and Parity Violation in the Capture of Cold Neutrons on B 4 C and (27) Al.

The NPDGamma γ-ray detector has been built to measure, with high accuracy, the size of the small parity-violating asymmetry in the angular distribution of gamma rays from the capture of polarized cold neutrons by protons. The high cold neutron flux at the Los Alamos Neutron Scattering Center (LANSCE) spallation neutron source and control of systematic errors require the use of current mode detection with vacuum photodiodes and low-noise solid-state preamplifiers. We show that the detector array operates at counting statistics and that the asymmetries due to B4C and (27)Al are zero to with- in 2 × 10(-6) and 7 × 10(-7), respectively.

Measurement of Parity Violation in np Capture: the NPDGamma Experiment.

The NPDGamma experiment will measure the parity-violating directional gamma ray asymmetry A γ in the reaction [Formula: see text]. Ultimately, this will constitute the first measurement in the neutron-proton system that is sensitive enough to challenge modern theories of nuclear parity violation, providing a theoretically clean determination of the weak pion-nucleon coupling. A new beam-line at the Los Alamos Neutron Science Center (LANSCE) delivers pulsed cold neutrons to the apparatus, where they are polarized by transmission through a large volume polarized (3)He spin filter and captured in a liquid para-hydrogen target.

Atomic Electric Dipole Moment Measurement Using Spin Exchange Pumped Masers of 129Xe and 3He.

We have measured the T-odd permanent electric dipole moment of 129Xe with spin exchange pumped masers and a 3He comagnetometer. The comagnetometer provides a direct measure of several systematic effects that may limit electric dipole moment sensitivity, and we have directly measured the effects of changes in leakage current that result when the applied electric field is changed. Our result, d(129Xe) = 0.

Distribution and dynamics of laser-polarized (129)Xe magnetization in vivo.

The first magnetic resonance imaging studies of laser-polarized (129)Xe, dissolved in the blood and tissue of the lungs and the heart of Sprague-Dawley rats, are described. (129)Xe resonances at 0, 192, 199, and 210 ppm were observed and assigned to xenon in gas, fat, tissue, and blood, respectively. One-dimensional chemical-shift imaging (CSI) reveals xenon magnetization in the brain, kidney, and lungs.

Brain MRI with laser-polarized 129Xe.

The feasibility of brain MRI with laser-polarized 129Xe in a small animal model is demonstrated. Naturally abundant 129Xe is polarized and introduced into the lungs of Sprague-Dawley rats. Polarized xenon gas dissolves in the blood and is transported to the brain where it accumulates in brain tissue.