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(Beta)-decay experiments and the unitarity of the CKM matrix

Description: The goal of this project was to perform very precise measurements of super-allowed Fermi {beta} decay in order to investigate a possible non-unitarity in the CKM matrix of the Standard Model of particle physics. Current data from 9 precisely measured {beta} decays indicated that the sum-of-squares of the first row of the CKM matrix differs from 1.0 at the 2.2{sigma} (or 98% confidence) level. If true, it would be the first firm indication of physics beyond the Standard Model--the model that has… more
Date: December 1, 2005
Creator: Garrett, P. E.
Partner: UNT Libraries Government Documents Department
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Quadrupole-octupole coupled states in 112Cd

Description: Negative-parity excitations in the 2.5 MeV region in {sup 112}Cd have been investigated with the (n,n`{gamma}) reaction. Several of these states exhibit enhanced B(E2) values for L decay to the 3{sub 1}{sup -} octupole state, indicative of quadrupole-octupole coupled (2{sup +} {circle_times} 3{sup -}) structures. The B(E1) values observed are typically in the range of 1-5 x 1O{sup -4} W u , irrespective of the final state.
Date: May 5, 1998
Creator: Garrett, P. E.
Partner: UNT Libraries Government Documents Department
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Low-Spin Collective Excitations in Deformed Nuclei: When is a B a B Vibration?

Description: The 0{sub 2}{sup +} level in deformed nuclei has historically been given the label {beta}, even though its properties vary drastically from one nucleus to another. By reviewing models from where the original term {beta} vibration arose, and appealing to microscopic calculations, guidelines are proposed for the properties of a true {beta} vibration. An examination of available data, including B(E2) values, {rho}{sup 2}(E0) values, and single- and two-nucleon-transfer populations, shows that very… more
Date: February 24, 2000
Creator: Garrett, P.E.
Partner: UNT Libraries Government Documents Department
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Nuclear structure of the Cd and Te nuclei: Akin to tin or a breed apart?

Description: Many of the {sub 48}Cd nuclei are good examples of U(5) or vibrational nuclei. Like the {sub 50}Sn nuclei and others in the region, states exist which are interpreted in terms of the excitation of a pair of protons across the shell gap (intruders). The features of the comparatively well-understood Cd nuclei will be considered and compared with the{sub 52}Te nuclei where intruders have not been identified experimentally and problems exist with the U(5) interpretation.
Date: December 20, 1999
Creator: Garrett, P E; Warr, N & Hicks, S F
Partner: UNT Libraries Government Documents Department
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Building a LLNL Capability in Radioactive Ion Beam Experiments

Description: The purpose of this LDRD was to establish a program at LLNL in radioactive ion beam (RIB) experiments that would use these experiments to address a wide range physics issues in both stellar nucleosynthesis and stockpile stewardship radiochemistry. The LDRD was funded for a total of two years (fiscal years 2000 and 2001) and transferred to the Physical Data Research Program in fiscal year 2002. Reactions on unstable nuclei and isomeric states play a central role in the formation of elements in b… more
Date: January 31, 2002
Creator: Bernstein, L. A.; Becker, J. A.; Garrett, P. E.; Younes, W. & Schiller, A.
Partner: UNT Libraries Government Documents Department
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Nuclear structure studies with the inelastic neutron scattering rection and gamma-ray detection

Description: The (<i>n</i>, <i>n</i>´(gamma)) reaction has been used at the University of Kentucky accelerator facility to examine the detailed structure of a number of nuclei. The advantages of this method are reviewed, and recent developments are described. Examples of unique nuclear structure studies that have been carried out with this method are presented.
Date: December 10, 1998
Creator: Garrett, P. E.; Warr, N. & Yates, S. W.
Partner: UNT Libraries Government Documents Department
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Determination of Partial (N,Xngamma) Cross-Sections in 193-Ir

Description: The {sup 193}Ir(n,n'){sup 193m}Ir cross section for the production of the 80-keV isomer in {sup 193}Ir is evaluated using a combination of experimental data and nuclear reaction modeling, from threshold to about 20 MeV. Four discrete {gamma} lines feeding the isomer were recently observed with the GEANIE {gamma}-ray detector at LANSCE. Theoretical calculations of the nuclear reaction mechanisms in play are then carried out to evaluate the contributions not accounted for in the experimental setu… more
Date: October 15, 2003
Creator: Talou, P.; Chadwick, M. B.; Nelson, R.; Fotiades, N.; Devlin, M.; Garrett, P. E. et al.
Partner: UNT Libraries Government Documents Department
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Uncertainty Budget and Efficiency Analysis for the 239Pu (n,2ny) Partial Reaction Cross-Section Measurements

Description: The {sup 239}Pu(n,2n{gamma}){sup 238}Pu partial reaction cross-section, {sigma}{sub (n,2n{gamma})}, has been measured as a function of neutron energy for several transitions in {sup 238}Pu. Partial {gamma}-ray cross sections for yrast, ''collector'' transitions, can provide especially valuable constraints on the magnitude and shape of the total (n,2n) reaction cross-section. In essence, nuclear reaction models will be used to infer the shape and magnitude of the total (n,2n) reaction cross-sect… more
Date: May 1, 2000
Creator: McNabb, D. P.; Archer, D. E.; Becker, J. A.; Bernstein, L. A. & Garrett, P. E.
Partner: UNT Libraries Government Documents Department
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Cross Sections for (Gamma)-Ray Production in the 191ir (N,Xn(Gamma)) Reactions

Description: Discrete {gamma}-ray spectra have been measured for nuclei populated in {sup 191}Ir(n{sub 4}xn{gamma}) with x{&lt;=}11, as a function of incident neutron energy using neutrons from the 'white' neutron source at the Los Alamos Neutron Science Center's WNR facility. The energy of the neutrons was determined using the time-of-flight technique. The data were taken using the GEANIE spectrometer. The cross sections for emission of 202 {gamma} rays of {sup 181-191}Ir were determined for neutron energi… more
Date: January 11, 2005
Creator: Fotiades, N.; Nelson, R. O.; Devlin, M.; Chadwick, M. B.; Talou, P.; Becker, J. A. et al.
Partner: UNT Libraries Government Documents Department
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Nuclear Structure Studies with GEANIE at the LANSCE/WNR Facility

Description: Recent results pertaining to nuclear structure from neutron-induced reactions on {sup 90}Zr, {sup 193}Ir, {sup 196}Pt and {sup 238}U are presented. The data were taken using the GEANIE spectrometer comprised of 26 high-purity Ge detectors with 20 BGO escape-suppression shields. The broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's WNR facility provided neutrons in the energy range from 0.6 to 200 MeV. The time-of-flight technique was used to determine the incident … more
Date: August 1, 2003
Creator: Fotiades, N.; Nelson, R. O.; Devlin, M.; Becker, J. A.; Garrett, P. E.; Younes, W. et al.
Partner: UNT Libraries Government Documents Department
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Cross Sections for n+89Y for En< 20 MeV

Description: Nuclear data collected in an experiment performed at LANSCE/WNR with the GEANIE spectrometer to measure the cross sections for n + {sup 89}Y for E{sub n} &lt; 20 MeV are reported. The estimated (n,2n) cross sections to the ground and isomeric states of {sup 88}Y differ significantly from those listed in the RADCHEM data base. Folded with a fast neutron spectrum, these results lead to integral differences of +15%, +2%, and -70% vs. the RADCHEM evaluation.
Date: April 18, 2003
Creator: Garrett, P. E.; Ormand, W. E.; Younes, W.; Becker, J. A.; Bernstein, L. A.; Nelson, R. O. et al.
Partner: UNT Libraries Government Documents Department
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E2 Transition Probabilities in 114Te: a Conundrum

Description: Lifetimes in {sup 114}Te were determined using the recoil distance Doppler-shift technique with a plunger device coupled to five HP Ge detectors enhanced by one Euroball Cluster detector. The experiment was carried out at the Cologne FN Tandem facility using the {sup 93}Nb({sup 24}Mg,p2n) reaction at 90 MeV. The differential decay curve method in coincidence mode was employed to derive lifetimes for seven excited states, while the lifetime of an isomeric state was obtained in singles mode. The … more
Date: May 13, 2005
Creator: Moller, O.; Warr, N.; Jolie, J.; Dewald, A.; Fitzler, A.; Linnemann, A. et al.
Partner: UNT Libraries Government Documents Department
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The 75As(n,2n) Cross Sections into the 74As Isomer and Ground State

Description: The {sup 75}As(n, 2n) cross section for the population of the T{sub 1/2} = 26.8-ns isomer at E{sub x} = 259.3 keV in {sup 74}As has been measured as a function of incident neutron energy, from threshold to E{sub n} = 20 MeV. The cross section was measured using the GEANIE spectrometer at LANSCE/WNR. For convenience, the {sup 75}As(n, 2n) population cross section for the {sup 74}As ground state has been deduced as the difference between the previously-known (n, 2n) reaction cross section and the… more
Date: June 30, 2003
Creator: Younes, W.; Garrett, P. E.; Becker, J. A.; Bernstein, L. A.; Ormand, W. E.; Dietrich, F. S. et al.
Partner: UNT Libraries Government Documents Department
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Establishment of M1 multipolarity of a 6.5 (micro)2n resonance in 172Yb at E(gamma) = 3.3 MeV

Description: Two-step-cascade spectra in {sup 172}Yb have been measured after thermal neutron capture. they are compared to calculations based on experimental values of the level density and radiative strength function (RSF) obtained from the {sup 173}Yb(3{sup 3}He,{alpha}{gamma}){sup 172}Yb reaction. The multipolarity of a 6.5(15) {mu}{sub N}{sup 2} resonance at E{sub {gamma}} = 3.3(1) MeV in the RSF is determined to be M1 by this comparison.
Date: February 4, 2004
Creator: Schiller, A.; Voinov, A.; Algin, E.; Becker, J. A.; Bernstein, L. A.; Garrett, P. E. et al.
Partner: UNT Libraries Government Documents Department
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Average Nuclear Level Densities and Radiative Strength Functions in {sup 56,57}FE from Primary (Gamma)-Ray Spectra

Description: An experimental primary {gamma}-ray spectrum vs. excitation-energy bin (P(E{sub x}, E{sub {gamma}}) matrix) in a light-ion reaction is obtained for {sup 56,57}Fe isotopes using a subtraction method. By factorizing the P(E{sub x}, E{sub {gamma}}) matrix according to the Axel-Brink hypothesis the nuclear level density and the radiative strength function (RSF) in {sup 56,57}Fe are extracted simultaneously. A step structure is observed in the level density for both isotopes, and is interpreted as t… more
Date: September 26, 2002
Creator: Tavukcu, E.; Becker, J. A.; Bernstein, L. A.; Garrett, P. E.; Guttormsen, M.; Mitchell, G. E. et al.
Partner: UNT Libraries Government Documents Department
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Thermodynamical Properties of 56Fe

Description: Average nuclear level densities close to the nuclear binding energy in {sup 56}Fe and {sup 57}Fe are extracted from primary {gamma}-ray spectra. Thermal properties of {sup 56}Fe are studied within the statistical canonical ensemble. The experimental heat capacity is compared with the theoretical heat capacity calculated within the shell model Monte Carlo approach.
Date: August 30, 2002
Creator: Tavukcu, E.; Becker, J. A.; Bernstein, L. A.; Garrett, P. E.; Guttormsen, M.; Mitchell, G. E. et al.
Partner: UNT Libraries Government Documents Department
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48Ti(n,xnypz ag) reactions for neutron energies up to 250 MeV

Description: Cross section measurements were made of prompt {gamma}-ray production as a function of incident neutron energy on a {sup 48}Ti sample. Partial {gamma}-ray cross sections for transitions in {sup 45--48}Ti, {sup 44--48}Sc, {sup 42--45}Ca, {sup 41--44}K, and {sup 41--42}Ar have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction {gamma} rays were detected with the large-scale Comp… more
Date: October 11, 2004
Creator: Dashdorj, D.; Garrett, P. E.; Becker, J. A.; Bernstein, L. A.; Cooper, J. R.; Devlin, M. et al.
Partner: UNT Libraries Government Documents Department
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Preliminary Report on the Population of the 235U T1/2=25-Minute Isomer by the (Nu,Nu'Gamma)Reaction

Description: The population cross section of the T{sub 1/2} = 25-minute, E{sub x} = 76.8-keV isomer in {sup 235}U via the {sup 235}U(n,n{prime}{gamma}) reaction has been estimated in the E{sub n} = 2.1-20-MeV range. Gamma rays populating both isomer and ground states were detected using the GEANIE spectrometer at the LANSCE/WNR ''white-source'' neutron facility. Partial {gamma}-ray cross sections were obtained as a function of incident neutron energy, using {gamma}-ray spectroscopy and the time-of-flight te… more
Date: October 9, 2002
Creator: Younes, W.; Britt, H. C.; Becker, J. A.; Bernstein, L. A.; Garrett, P. E.; McGrath, C. A. et al.
Partner: UNT Libraries Government Documents Department
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Nuclear modeling of (n, x, [gamma]) reactions and determination of partial cross sections

Description: This talk would describe nuclear reaction modeling work in collaboration with experimental measurements at Los Alamos' GEANIE array. The GEANIE array is able to measure discrete gamma-rays in the deexcitation of residual nuclei produced following neutron-induced reactions, using time-of-flight with a white neutron spectrum. We have studied reactions on a range of target nuclides including actinides (eg 239Pu, 235,8U) as well as dosimetry materials (eg Y89, 193Ir). Since GEANIE is unable to meas… more
Date: January 1, 2002
Creator: Chadwick, M. B. (Mark B.); Talou, P. (Patrick); Young, P. G. (Phillip Gaffney),; Blann, M. (Marshall); Nelson, R. O. (Ronald O.); Garrett, P. E. (Paul E.) et al.
Partner: UNT Libraries Government Documents Department
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Radiative Strength Functions in 172yb Below 8 Me V

Description: We have measured prompt {gamma} rays after thermal and resonant neutron capture in {sup 171}Yb. The {gamma} rays were measured with three high resolution ({approx}3 keV) and high efficiency (two {approx}80% Ge(HP) and one {approx}200% segmented Clover) detectors. We have obtained singles and two-fold coincidence spectra as function of neutron energy using the time-of-flight technique. Two-fold coincidences where the summed energy adds up to the neutron binding energy B{sub n} or to B{sub n} min… more
Date: February 6, 2002
Creator: Schiller, A.; Becker, J. A.; Bernstein, L. A.; Garrett, P. E.; Hill, T. S.; McNabb, D. P. et al.
Partner: UNT Libraries Government Documents Department
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Transition from Asymmetric to Symmetric Fission in the 235U(n,f) Reaction

Description: Prompt {gamma} rays from the neutron-induced fission of {sup 235}U have been studied using the GEANIE spectrometer situated at the LANSCE/WNR ''white'' neutron facility. Gamma-ray production cross sections for 29 ground-state-band transitions in 18 even-even fission fragments were obtained as a function of incident neutron energy, using the time-of-flight technique. Independent yields were deduced from these cross sections and fitted with standard formulations of the fragment charge and mass di… more
Date: July 19, 2001
Creator: Younes, W.; Becker, J. A.; Bernstein, L. A.; Garrett, P. E.; McGrath, C. A.; McNabb, D. P. et al.
Partner: UNT Libraries Government Documents Department
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Nuclear Science at GEANIE

Description: GEANIE at LANSCE/WNR combines the precision energy resolution of germanium detectors with the advantages of a white source providing neutrons with energies 1 &lt; E{sub n}(MeV) &lt; 250 to address a variety of topics in nuclear physics. The authors present the analysis of two data sets, n+{sup 235}U and n+{sup 92}Mo, acquired at GEANIE during the 1998 beam cycle. These data showcase the breadth of subjects under study at this facility, including the spectroscopy of stable and near-stable nuclei… more
Date: December 17, 1999
Creator: Younes, W.; Becker, J. A.; Bernstein, L. A.; Garrett, P. E.; McNabb, D. P.; McGrath, C. A. et al.
Partner: UNT Libraries Government Documents Department
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