Kevin Patrick Coulter

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

The first magnetic resonance imaging studies of laser‐polarized 129Xe, dissolved in the blood and tissue of the lungs and the heart of Sprague‐Dawley rats, are described. 129Xe 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. Coronal and axial two‐dimensional CSI show 129Xe dissolved in blood and tissue in the thorax. Images of the blood resonance show xenon in the lungs and the heart ventricle. Images of the tissue resonance reveal xenon in lung parenchyma and myocardium. The 129Xe spectrum from a voxel located in the heart ventricle shows a single blood resonance. Time‐resolved spectroscopy shows that the dynamics of the blood resonance match the dynamics of the gas resonance and demonstrates efficient diffusion of xenon gas to the lung parenchyma and then to pulmonary blood. These observations demonstrate the utility of laser‐polarized 129Xe to detect exchange across the gas‐blood barrier in the lungs and perfusion into myocardial tissue. Applications to measurement of lung function, kidney perfusion, myocardial perfusion, and regional cerebral blood flow are discussed. Magn Reson Med 42:1137–1145, 1999.

Polarized 129Xe optical pumping/spin exchange and delivery system for magnetic resonance spectroscopy and imaging studies

We describe the design and construction of a laser-polarized 129Xe production and delivery system that is used in our in vitro and in vivo magnetic resonance imaging (MRI) experiments. The entire apparatus including lasers and optics, rapidly actuated valves, heating and cooling, and transport tubing lies in the high magnetic field environment of a 2 T MRI magnet. With approximately 7.5% 129Xe polarization, 157 cc atm of xenon gas is produced and stored as xenon ice every 5 min. Large quantities of polarized 129Xe can be obtained by cycling this process. The xenon is subsequently delivered in a controlled fashion to a sample or subject. With this device we have established the feasibility of using laser-polarized 129Xe as a magnetic tracer in MRI. This reliable, effective, and relatively simple production method for large volumes of 129Xe can be applied to other areas of research involving the use of laser-polarized noble gases.

New limit on the D coefficient in polarized neutron decay

We describe an experiment that has set new limits on the time reversal invariance violating D coefficient in neutron beta-decay. The emiT experiment measured the angular correlation J . p_e x p_p using an octagonal symmetry that optimizes electron-proton coincidence rates. The result is D=[-0.6+/-1.2(stat)+/-0.5(syst)]x10^(-3). This improves constraints on the phase of g_A/g_V and limits contributions to T violation due to leptoquarks. This paper presents details of the experiment, data analysis, and the investigation of systematic effects.

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±1.89(stat)±1.01(sys)]×10(-4). The corresponding phase between gA and gV is ϕAV=180.013°±0.028° (68% confidence level). This result represents the most sensitive measurement of D in nuclear β decay.

Polarization of 129Xe with high power external-cavity laser diode arrays

We demonstrate narrowing of a 2 W, broad area laser diode array and present calculations of the resulting improvement of 129Xe polarization by spin exchange with laser optically pumped Rb vapor. This improvement significantly impacts both medical imaging with laser polarized noble gas and spin-exchange pumped noble gas maser research.

Measurement of the parity violating asymmetry Aγ in n→+p→d+γ

The weak pion-nucleon coupling constant H{sub {pi}}{sup 1} remains poorly determined, despite many years of effort. The recent measurement of the {sup 133}Cs anapole moment has been interpreted to give a value of H{sub {pi}}{sup 1} almost an order of magnitude larger than the limit established in the {sup 18}F parity doublet experiments. A measurement of the gamma ray directional asymmetry A{sub {gamma}} for the capture of polarized neutrons by hydrogen has been proposed at Los Alamos National Laboratory. This experiment will determine H{sub {pi}}{sup 1} independent of nuclear structure effects. However, since the predicted asymmetry is small, A{sub {gamma}} {approximately} 5 x 10{sup {minus}8}, systematic effects must be reduced to < 5 x 10{sup {minus}9}. The design of the experiment will is presented, with an emphasis on the techniques used for controlling systematic errors.

Search for a T-odd, P-even Triple Correlation in Neutron Decay

Search for a T-odd, P-even Triple Correlation in Neutron Decay T.E. Chupp, 1 R.L. Cooper, 1 K.P. Coulter, 1 S.J. Freedman, 2 B.K. Fujikawa, 2 A. Garc´ia, 3, 4 G.L. Jones, 5 H.P. Mumm, 6 J.S. Nico, 6 A.K. Thompson, 6 C.A. Trull, 7 F.E. Wietfeldt, 7 and J.F. Wilkerson 3, 8, 9 University of Michigan, Ann Arbor, Michigan 48104, USA Physics Department, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA CENPA and Physics Department, University of Washington, Seattle, WA 98195 USA Department of Physics, University of Notre Dame, Notre Dame, IN 46556 USA Physics Department, Hamilton College, Clinton, NY 13323, USA National Institute of Standards and Technology, Gaithersburg, MD 20899, USA Physics Department, Tulane University, New Orleans, LA 70118, USA Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599, USA Oak Ridge National Lab, Oak Ridge, TN, 37831 USA Background: Time-reversal-invariance violation, or equivalently CP violation, may explain the observed cosmological baryon asymmetry as well as signal physics beyond the Standard Model. In the decay of polarized neutrons, the triple correlation D J n ·(p e ×p ν ) is a parity-even, time-reversal- odd observable that is uniquely sensitive to the relative phase of the axial-vector amplitude with respect to the vector amplitude. The triple correlation is also sensitive to possible contributions from scalar and tensor amplitudes. Final-state effects also contribute to D at the level of 10 −5 and can be calculated with a precision of 1% or better. Purpose: We have improved the sensitivity to T-odd, P-even interactions in nuclear beta decay. Methods: We measured proton-electron coincidences from decays of longitudinally polarized neutrons with a highly symmetric detector array designed to cancel the time-reversal-even, parity-odd Standard-Model contributions to polarized neutron decay. Over 300 million proton-electron coincidence events were used to extract D and study systematic effects in a blind analysis. Results: We find D = [−0.94 ± 1.89(stat) ± 0.97(sys)] × 10 −4 . Conclusions: This is the most sensitive measurement of D in nuclear beta decay. Our result can be interpreted as a measurement of the phase of the ratio of the axial-vector and vector coupling constants (C A /C V = |λ|e iφ AV ) with φ AV = 180.012 ◦ ±0.028 ◦ (68% confidence level) or to constrain time-reversal violating scalar and tensor interactions that arise in certain extensions to the Standard Model such as leptoquarks. This paper presents details of the experiment, analysis, and systematic- error corrections. PACS numbers: 24.80.+y, 11.30.Er, 12.15.Ji, 13.30.Ce DISCLAIMER: This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of Cal- ifornia, nor any of their employees, makes any warranty, express or implied, or assumes any le- gal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, prod- uct, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommen- dation, or favoring by the United States Govern- ment or any agency thereof, or the Regents of the University of California. The views and opin- ions of authors expressed herein do not necessar- ily state or reflect those of the United States Gov- ernment or any agency thereof or the Regents of the University of California. I. INTRODUCTION The symmetries of physical processes under the trans- formations of charge conjugation (C), parity (P), and time reversal (T) have played a central role in the de- velopment of the Standard Model of elementary-particle interactions [1]. Time-reversal-symmetry violation (or T violation), which is equivalent to CP violation assum- ing CPT symmetry, has been of particular interest be- cause it is sensitive to many kinds of new physics. The CP-violating parameters of the Standard Model are the Cabibbo-Kobayashi-Maskawa (CKM) phase, which en- ters in the mixing of three generations of quarks, and the parameter θ QCD . The effect of the CKM phase is strongly suppressed in the permanent electric dipole mo- ments (EDMs) of the neutron [2] and heavy atoms [3, 4], and recent EDM results combine to set upper limits on θ QCD . All laboratory measurements to date are consis- tent with a single source of CP violation, i.e. the phase in the CKM matrix. An exception may be the 3.2 sigma deviation observed recently as an asymmetry in the pro- duction of pairs of like-sign muons reported by the D0

Magnetic resonance imaging with laser-polarized 129Xe

Abstract To investigate the feasibility of magnetic resonance imaging with laser-polarized 129 Xe we have undertaken the study of time dependences of the 129 Xe magnetization in the whole body and its build-up in the brain. We conclude that by increasing the production and absolute polarization of the 129 Xe, it will be possible to apply this technique to human brain activation studies based on quantitative measurement of regional cerebral blood flow.

A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La

Abstract An apparatus for measuring parity-violating asymmetries in gamma-ray emission following polarized cold neutron capture was constructed as a 1/10th scale test of the design for the forthcoming n → + p → d + γ experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3 He neutron spin filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl) detectors and photodiode current mode readout, measurements were made of asymmetries in gamma-ray emission following neutron capture on 35 Cl , 113 Cd , and 139 La targets. Upper limits on the parity-allowed asymmetry s n ·( k γ × k n ) were set at the level of 7×10 −6 for all three targets. Parity-violating asymmetries s n · k γ were observed in 35 Cl , A γ =(−29.1±6.7)×10 −6 , and 139 La , A γ =(−15.5±7.1)×10 −6 , values consistent with previous measurements.

Recent advances in spin-exchange pumped polarized 3He target technology

Abstract We have produced long lifetime 3 He spin-exchange cells from Corning 7056 glass. The lifetimes of single cells have approached the 3 He 3 He bulk-limited lifetime (250 h at a density of 8 × 10 19 cm −3 , (3 amagats)). Corning 7056 glass has the advantage of being a much easier glass for the glassblower to work, allowing for more complex cell designs. In our experiments at Michigan and at SLAC, we have implemented laser diode arrays for spin-exchange optical pumping. In particular, for experiment E154 at SLAC, we achieved high polarizations in high-density 3 He targets using laser diode arrays.