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Search Results: 1 - 10 of 521230 matches for " M. T. W. Gericke "
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The NPDGamma Experiment at LANSCE
M. T. Gericke,for the NPDGamma Collaboration
Physics , 2005,
Abstract: The NPDGamma collaboration has constructed and commissioned an apparatus to determine the size of the pion-nucleon coupling constant in the parity non conserving pion exchange weak potential for N-N interactions. This coupling constant is directly proportional to the parity violating up-down asymmetry in the angular distribution of gamma rays with respect to the neutron spin direction in the capture of polarized cold neutrons on protons. The measurement of the weak pNN coupling will provide a test for the effective theory, describing the nucleon-nucleon interaction as mediated by the exchange of mesons, and provide results against which to compare models describing QCD at low energy. NPDGamma is located at the Los Alamos Neutron Science Center (LANSCE) and utilizes the special features of cold spallation neutrons to make it possible to measure very small gamma ray asymmetries. In this paper, we present the motivation for the experiment and report on experimental setup as well as the current status of the project and the results obtained during the 2004 commissioning run including parity violation asymmetry measurements on Al, CCL4, In, Boron-Carbide, and Cu.
A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La
G. S. Mitchell,C. S. Blessinger,J. D. Bowman,T. E. Chupp,K. P. Coulter,M. T. W. Gericke,G. L. Jones,M. B. Leuschner,H. Nann,S. A. Page,S. I. Penttila,T. B. Smith,W. M. Snow,W. S. Wilburn
Physics , 2004, DOI: 10.1016/j.nima.2003.11.192
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+gamma experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3He 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 35Cl, 113Cd, and 139La targets. Upper limits on the parity-allowed asymmetry $s_n \cdot (k_{\gamma} \times k_n)$ were set at the level of 7 x 10^-6 for all three targets. Parity-violating asymmetries $s_n \cdot k_{\gamma}$ were observed in 35Cl, A_gamma = (-29.1 +- 6.7) x 10^-6, and 139La, A_gamma = (-15.5 +- 7.1) x 10^-6, values consistent with previous measurements.
A Current Mode Detector Array for Gamma-Ray Asymmetry Measurements
M. T. Gericke,C. Blessinger,J. D. Bowman,R. C. Gillis,J. Hartfield,T. Ino,M. Leuschner,Y. Masuda,G. S. Mitchell,S. Muto,H. Nann,S. A. Page,S. I. Penttil{?}},W. D. Ramsay,P. -N. Seo,W. M. Snow,J. Tasson,W. S. Wilburn
Physics , 2004, DOI: 10.1016/j.nima.2004.11.043
Abstract: We have built a CsI(Tl) gamma-ray detector array for the NPDGamma experiment to search for a small parity-violating directional asymmetry in the angular distribution of 2.2 MeV gamma-rays from the capture of polarized cold neutrons by protons with a sensitivity of several ppb. The weak pion-nucleon coupling constant can be determined from this asymmetry. The small size of the asymmetry requires a high cold neutron flux, control of systematic errors at the ppb level, and the use of current mode gamma-ray detection with vacuum photo diodes and low-noise solid-state preamplifiers. The average detector photoelectron yield was determined to be 1300 photoelectrons per MeV. The RMS width seen in the measurement is therefore dominated by the fluctuations in the number of gamma rays absorbed in the detector (counting statistics) rather than the intrinsic detector noise. The detectors were tested for noise performance, sensitivity to magnetic fields, pedestal stability and cosmic background. False asymmetries due to gain changes and electronic pickup in the detector system were measured to be consistent with zero to an accuracy of $10^{-9}$ in a few hours. We report on the design, operating criteria, and the results of measurements performed to test the detector array.
Ultracold Atoms as a Target: Absolute Scattering Cross-Section Measurements
P. Würtz,T. Gericke,A. Vogler,H. Ott
Physics , 2010, DOI: 10.1088/1367-2630/12/6/065033
Abstract: We report on a new experimental platform for the measurement of absolute scattering cross-sections. The target atoms are trapped in an optical dipole trap and are exposed to an incident particle beam. The exponential decay of the atom number directly yields the absolute total scattering cross-section. The technique can be applied to any atomic or molecular species that can be prepared in an optical dipole trap and provides a large variety of possible scattering scenarios.
Upper Bounds on Parity Violating Gamma-Ray Asymmetries in Compound Nuclei from Polarized Cold Neutron Capture
M. T. Gericke,J. D. Bowman,R. D. Carlini,T. E. Chupp,K. P. Coulter,M. Dabaghyan,M. Dawkins,D. Desai,S. J. Freedman,T. R. Gentile,R. C. Gillis,G. L. Greene,F. W. Hersman,T. Ino,G. L. Jones,M. Kandes,B. Lauss,M. Leuschner,W. R. Lozowski,R. Mahurin,M. Mason,Y. Masuda,G. S. Mitchell,S. Muto,H. Nann,S. A. Page,S. I. Penttila,W. D. Ramsay,S. Santra,P. -N. Seo,E. I. Sharapov,T. B. Smith,W. M. Snow,W. S. Wilburn,V. Yuan,H. Zhu
Physics , 2006, DOI: 10.1103/PhysRevC.74.065503
Abstract: Parity-odd asymmetries in the electromagnetic decays of compound nuclei can sometimes be amplified above values expected from simple dimensional estimates by the complexity of compound nuclear states. In this work we use a statistical approach to estimate the root mean square (RMS) of the distribution of expected parity-odd correlations $\vec{s_{n}} \cdot \vec{k_{\gamma}}$, where $\vec {s_{n}}$ is the neutron spin and $\vec{k_{\gamma}}$ is the momentum of the gamma, in the integrated gamma spectrum from the capture of cold polarized neutrons on Al, Cu, and In and we present measurements of the asymmetries in these and other nuclei. Based on our calculations, large enhancements of asymmetries were not predicted for the studied nuclei and the statistical estimates are consistent with our measured upper bounds on the asymmetries.
High-Efficiency Resonant RF Spin Rotator with Broad Phase Space Acceptance for Pulsed Polarized Cold Neutron Beams
P. -N. Seo,L. Barron-Palos,J. D. Bowman,T. E. Chupp,C. Crawford,M. Dabaghyan,M. Dawkins,S. J. Freedman,T. Gentile,M. T. Gericke,R. C. Gillis,G. L. Greene,F. W. Hersman,G. L. Jones,M. Kandes,S. Lamoreaux,B. Lauss,M. B. Leuschner,R. Mahurin,M. Mason,J. Mei,G. S. Mitchell,H. Nann,S. A. Page,S. I. Penttila,W. D. Ramsay,A. Salas Bacci,S. Santra,M. Sharma,T. B. Smith,W. M. Snow,W. S. Wilburn,H. Zhu
Physics , 2007, DOI: 10.1103/PhysRevSTAB.11.084701
Abstract: We have developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5 cm x 9.5 cm pulsed cold neutron beam with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to RF neutron spin flippers based on adiabatic fast passage. The spin rotator does not change the kinetic energy of the neutrons and leaves the neutron beam phase space unchanged to high precision. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically-polarized 3He neutron spin filters. The efficiency of the spin rotator was measured to be 98.0+/-0.8% on resonance for neutron energies from 3.3 to 18.4 meV over the full phase space of the beam. As an example of the application of this device to an experiment we describe the integration of the RF spin rotator into an apparatus to search for the small parity-violating asymmetry A_gamma in polarized cold neutron capture on para-hydrogen by the NPDGamma collaboration at LANSCE.
Nab: Measurement Principles, Apparatus and Uncertainties
Pocanic, D.;Alarcon, R.;Alonzi, L. P.;Baessler, S.;Balascuta, S.;Bowman, J. D.;Bychkov, M. A.;Byrne, J.;Calarco, J. R.;Cianciolo, V.;Crawford, C.;Frlez, E.;Gericke, M. T.;Greene, G. L.;Grzywacz, R. K.;Gudkov, V.;Hersman, F. W.;Klein, A.;Martin, J.;Page, S. A.;Palladino, A.;Penttila, S. I.;Rykaczewski, K. P.;Wilburn, W. S.;Young, A. R.;Young, G. R.
High Energy Physics - Phenomenology , 2008,
Abstract: The Nab collaboration will perform a precise measurement of 'a', the electron-neutrino correlation parameter, and 'b', the Fierz interference term in neutron beta decay, in the Fundamental Neutron Physics Beamline at the SNS, using a novel electric/magnetic field spectrometer and detector design. The experiment is aiming at the 10^{-3} accuracy level in (Delta a)/a, and will provide an independent measurement of lambda = G_A/G_V, the ratio of axial-vector to vector coupling constants of the nucleon. Nab also plans to perform the first ever measurement of 'b' in neutron decay, which will provide an independent limit on the tensor weak coupling.
Nab: Measurement Principles, Apparatus and Uncertainties
D. Pocanic,R. Alarcon,L. P. Alonzi,S. Baessler,S. Balascuta,J. D. Bowman,M. A. Bychkov,J. Byrne,J. R. Calarco,V. Cianciolo,C. Crawford,E. Frlez,M. T. Gericke,G. L. Greene,R. K. Grzywacz,V. Gudkov,F. W. Hersman,A. Klein,J. Martin,S. A. Page,A. Palladino,S. I. Penttila,K. P. Rykaczewski,W. S. Wilburn,A. R. Young,G. R. Young
Physics , 2008, DOI: 10.1016/j.nima.2009.07.065
Abstract: The Nab collaboration will perform a precise measurement of 'a', the electron-neutrino correlation parameter, and 'b', the Fierz interference term in neutron beta decay, in the Fundamental Neutron Physics Beamline at the SNS, using a novel electric/magnetic field spectrometer and detector design. The experiment is aiming at the 10^{-3} accuracy level in (Delta a)/a, and will provide an independent measurement of lambda = G_A/G_V, the ratio of axial-vector to vector coupling constants of the nucleon. Nab also plans to perform the first ever measurement of 'b' in neutron decay, which will provide an independent limit on the tensor weak coupling.
AC-Stark shift and photoionization of Rydberg atoms in an optical dipole trap
F. Markert,P. Würtz,A. Koglbauer,T. Gericke,A. Vogler,H. Ott
Physics , 2010, DOI: 10.1088/1367-2630/12/11/113003
Abstract: We have measured the AC-Stark shift of the $14D_{5/2}$ Rydberg state of rubidium 87 in an optical dipole trap formed by a focussed CO$_2$-laser. We find good quantitative agreement with the model of a free electron experiencing a ponderomotive potential in the light field. In order to reproduce the observed spectra we take into account the broadening of the Rydberg state due to photoionization. The extracted cross-section is compatible with previous measurements on neighboring Rydberg states.
Neutron Beta Decay Studies with Nab
S. Bae?ler,R. Alarcon,L. P. Alonzi,S. Balascuta,L. Barrón-Palos,J. D. Bowman,M. A. Bychkov,J. Byrne,J. R. Calarco,T. Chupp,T. V. Vianciolo,C. Crawford,E. Frle?,M. T. Gericke,F. Glück,G. L. Greene,R. K. Grzywacz,V. Gudkov,D. Harrison,F. W. Hersman,T. Ito,M. Makela,J. Martin,P. L. McGaughey,S. McGovern,S. Page,S. I. Penttil?,D. Po?ani?,K. P. Rykaczewski,A. Salas-Bacci,Z. Tompkins,D. Wagner,W. S. Wilburn,A. R. Young
Physics , 2012, DOI: 10.1063/1.4826731
Abstract: Precision measurements in neutron beta decay serve to determine the coupling constants of beta decay and allow for several stringent tests of the standard model. This paper discusses the design and the expected performance of the Nab spectrometer.
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