7,464 Matching Results

Search Results

Advanced search parameters have been applied.

The Thickness Distortion of Fe 57 Backscatter Mossbauer Spectra

Description: The thickness distortion of a backscatter 14.41 keV {gamma}-ray Mossbauer spectrum is calculated for the case of isotropic {gamma}-ray re-emission in the absorber, and a method of extracting the true absorber material resonant scattering cross section from experimental data is suggested and demonstrated. Some other features of backscatter and transmission Fe{sup 57} Mossbauer spectra are compared.
Date: August 1, 1980
Creator: Fultz, B. & Morris, J. W., Jr.
Partner: UNT Libraries Government Documents Department

Nuclear spectroscopy with direct relations [Part] 2. Proceedings

Description: The Symposium on Nuclear Spectroscopy with Direct Reactions, sponsored and organized by Argonne National Laboratory under the auspices of the U. S. Atomic Energy Commission, was held on 9-11 March 1964 at the Center for Continuing Education, University of Chicago. The present volume contains the invited papers along with abstracts or summaries of the few short papers selected for their special relevance to the topics of the invited lecturers . Edited versions of the discussions are also included.
Date: March 1, 1964
Creator: Throw, F. E.
Partner: UNT Libraries Government Documents Department

Measurement of single-target spin asymmetries in the electroproduction of negative pions in the semi-inclusive deep inelastic reaction n{up_arrow}(e,e'{pi}{sup -})X on a transversely polarized {sup 3}He target

Description: The experiment E06010 measured the target single spin asymmetry (SSA) in the semiinclusive deep inelastic (SIDIS) n{up_arrow}(e, e'{pi}{sup -})X reaction with a transversely polarized {sup 3}He target as an e#11;ective neutron target. This is the very #12;rst independent measurement of the neutron SSA, following the measurements at HERMES and COMPASS on the proton and the deuteron. The experiment acquired data in Hall A at Je#11;erson Laboratory with a continuous electron beam of energy 5.9 GeV, probing the valence quark region, with x = 0.13 {rt_arrow} 0.41, at Q{sup 2} = 1.31 {rt_arrow} 3.1 GeV{sup 2}. The two contributing mechanisms to the measured asymmetry, viz, the Collins effect and the Sivers effect can be realized through the variation of the asymmetry as a function of the Collins and Sivers angles. The neutron Collins and Sivers moments, associated with the azimuthal angular modulations, are extracted from the measured asymmetry for the very #12;first time and are presented in this thesis. The kinematics of this experiment is comparable to the HERMES proton measurement. However, the COMPASS measurements on deuteron and proton are in the low-x region. The results of this experiment are crucial as the first step toward the extraction of quark transversity and Sivers distribution functions in SIDIS. With the existing results on proton and deuteron, these new results on neutron will provide powerful constraints on the transversity and Sivers distributions of both the u and d-quarks in the valence region.
Date: June 1, 2010
Creator: Dutta, Chiranjib
Partner: UNT Libraries Government Documents Department

Photodisintegration of Light Nuclei with CLAS

Description: We report preliminary results of photodisintegration of deuteron and {sup 3}He measured with CLAS at Jefferson Lab. We have extracted the beam-spin asymmetry for the {vector {gamma}}d {yields} pn reaction at photon energies from 1.1 GeV to 2.3 GeV and proton center-of-mass (c.m.) angles between 35{degrees}#14; and 135{degrees}#14;. Our data show interesting evolution of the angular dependence of the observable as the photon energy increases. The energy dependence of the beam-spin asymmetry at 90#14; shows a change of slope at photon energy of 1.6 GeV. A comparison of our data with model calculations suggests that a fully non-perturbative treatment of the underlying dynamics may be able to describe the data better than a model based on hard scattering. We have observed onset of dimensional scaling in the cross section of two-body photodisintegration of {sup 3}He at remarkably low energy and momentum transfer, which suggests that partonic degrees of freedom may be relevant for the description of nuclei at energies lower than previously considered.
Date: August 1, 2013
Creator: Ilieva, Yordanka Yordanova & Zachariou, Nicholas
Partner: UNT Libraries Government Documents Department

Nuclear electromagnetic charge and current operators in Chiral EFT

Description: We describe our method for deriving the nuclear electromagnetic charge and current operators in chiral perturbation theory, based on time-ordered perturbation theory. We then discuss possible strategies for fixing the relevant low-energy constants, from the magnetic moments of the deuteron and of the trinucleons, and from the radiative np capture cross sections, and identify a scheme which, partly relying on {Delta} resonance saturation, leads to a reasonable pattern of convergence of the chiral expansion.
Date: August 1, 2013
Creator: Girlanda, Luca; Marcucci, Laura Elisa; Pastore, Saori; Piarulli, Maria; Schiavilla, Rocco & Viviani, Michele
Partner: UNT Libraries Government Documents Department

Meausrement of the Neutron Radius of {sup 208}Pb Through Parity Violation in Electron Scattering

Description: In contrast to the nuclear charge densities, which have been accurately measured with electron scattering, the knowledge of neutron densities still lack precision. Previous model-dependent hadron experiments suggest the difference between the neutron radius, R{sub n}, of a heavy nucleus and the proton radius, R{sub p}, to be in the order of several percent. To accurately obtain the difference, R{sub n}-R{sub p}, which is essentially a neutron skin, the Jefferson Lab Lead ({sup 208}Pb) Radius Experiment (PREX) measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from {sup 208}Pb at an energy of 1.06 GeV and a scattering angle of 5{degrees}#14;. Since Z{sup 0} boson couples mainly to neutrons, this asymmetry provides a clean measurement of R{sub n} with respect to R{sub p}. PREX was conducted at the Jefferson lab experimental Hall A, from March to June 2010. The experiment collected a final data sample of 2x#2;10{sup 7} helicity-window quadruplets. The measured parity-violating electroweak asymmetry A{sub PV} = 0.656 {+-}#6; 0.060 (stat) {+-}#6; 0.014 (syst) ppm corresponds to a difference between the radii of the neutron and proton distributions, R{sub n}-R{sub p} = 0.33{sup +0.16}{sub -0.18} fm and provides the #12;first electroweak observation of the neutron skin as expected in a heavy, neutron-rich nucleus. The value of the neutron radius of {sup 208}Pb has important implications for models of nuclear structure and their application in atomic physics and astrophysics such as atomic parity non-conservation (PNC) and neutron stars.
Date: May 31, 2013
Creator: Saenboonruang, Kiadtisak
Partner: UNT Libraries Government Documents Department

Study of the (e,e'p) quasi-elastic reaction in complex nuclei: theory and experiment

Description: Experimental coincidence cross section and transverse-longitudinal asymmetry A{sub TL} have been obtained for the quasielastic (e,e'p) reaction in {sup 16}O, {sup 12}C, and {sup 208}Pb in constant q-ω kinematics in the missing momentum range -350 < p{sub miss} < 350 MeV/c. In these experiments, performed in experimental Hall A of the Thomas Jefferson National Accelerator Facility (JLAB), the beam energy and the momentum and angle of the scattered electrons were kept fixed, while the angle between the proton momentum and the momentum transfer q was varied in order to map out the missing momentum distribution. The experimental cross section and A{sub TL} asymmetry have been compared with Monte Carlo simulations based on Distorted Wave Impulse Approximation (DWIA) calculations with both relativistic and non-relativistic spinor structure. The spectroscopic factors obtained for both models are in agreement with previous experimental values, while A{sub TL} measurements favor the relativistic DWIA calculation. This thesis describes the details of the experimental setup, the calibration of the spectrometers, the techniques used in the data analysis to derive the final cross sections and the A{sub TL}, the ingredients of the theoretical calculations employed and the comparison of the results with the simulations based on these theoretical models.
Date: March 1, 2010
Creator: Herraiz, Joaquin Lopez
Partner: UNT Libraries Government Documents Department

GFMC calculations of electromagnetic moments and M1 transitions in A {<=} 9 nuclei

Description: We present recent Green’s function Monte Carlo calculations of magnetic moments and M1 transitions in A{<=}#20;9 nuclei, which include corrections arising from two-body meson-exchange electromagnetic currents. Two-body effects provide significant corrections to the calculated observables, bringing them in excellent agreement with the experimental data. In particular, we find that two body corrections are especially large in the A = 9, T = 3/2 systems, in which they account for up to ~#24; 20% (~#24; 40%) of the total predicted value for the {sup 9}Li ({sup 9}C) magnetic moment.
Date: August 1, 2013
Creator: Pastore, Saori; Pieper, Steven C.; Schiavilla, Rocco & Wiringa, Robert Bruce
Partner: UNT Libraries Government Documents Department

Measurement of the Electric and Magnetic Elastic Structure Functions of the Deuteron at Large Momentum Transfers

Description: The deuteron elastic structure functions, A(Q{sup 2}) and B(Q{sup 2}), have been extracted from cross section measurements of elastic electron-deuteron scattering in coincidence using the Continuous Electron Beam Accelerator and Hall A Facilities of Jefferson Laboratory. Incident electrons were scattered off a high-power cryogenic deuterium target. Scattered electrons and recoil deuterons were detected in the two High Resolution Spectrometers of Hall A. A(Q{sup 2}) was extracted from forward angle cross section measurements in the squared four-momentum transfer range 0.684 ≤ Q{sup 2} ≤ 5.90 (GeV/c){sup 2}. B(Q{sup 2}) was determined by means of a Rosenbluth separation in the range 0.684 ≤ Q{sup 2} ≤ 1.325 (GeV/c){sup 2}. The data are compared to theoretical models based on the impulse approximation with the inclusion of meson-exchange currents and to predictions of quark dimensional scaling and perturbative quantum chromodynamics. The results are expected to provide insights into the transition from meson-nucleon to quark-gluon descriptions of the nuclear two-body system.
Date: October 1, 1999
Creator: Suleiman, Riad
Partner: UNT Libraries Government Documents Department

Measurement of the deuteron elastic structure functions at large momentum transfers

Description: The cross section for elastic electron-deuteron scattering has been measured using the Hall A Facility of Jefferson Laboratory. Scattered electrons and recoiling deuterons were detected in coincidence in the two 4 GeV/c High Resolution Spectrometers (HRS) of Hall A. The deuteron elastic structure functions A(Q{sup 2}) and B(Q{sup 2}) have been extracted from these data. Results for the measurement of A(Q{sup 2}) in the range of 0.7 ≤ Q{sup 2} ≤ 6.0 (GeV/c){sup 2} are reported. Results for the magnetic structure function, B(Q{sup 2}), are presented in the range of 0.7 ≤ Q{sup 2} ≤ 1.35 (GeV/c){sup 2}. The results for both structure functions are compared to predictions of meson-nucleon based models, both with and without the inclusion of meson-exchange currents. The A(Q{sup 2}) results are compared to predictions of the dimensional scaling quark model and perturbative quantum chromodynamics. The results can provide insights into the transition from meson-nucleon to quark-gluon descriptions of the nuclear two-body system.
Date: August 1, 1999
Creator: McCormick, Kathy
Partner: UNT Libraries Government Documents Department

A study of the {sup 16}O (e, e'p) reaction at deep missing energies

Description: The {sup 16}O(e,e'p)#8; reaction was studied in the #6;first physics experiment performed at Jefferson lab Hall A. In the quasielastic region cross sections were measured for both quasi#11;parallel and perpendicular kinematics at q = 1000 MeV and #2;{omega} = 445#14;#14;#15; MeV. From the data acquired in quasi#11;parallel kinematics#4; longitudinal and transverse response functions#4; R{sub L} and R{sub T} were separated for E{sub miss} < 60 MeV. The perpendicular kinematics data were used to extract R{sub LT}, #4; R{sub T},#4; and R{sub L#16;} + V{sub TT}/V{sub L}R{sub TT} response functions for the same E{sub miss} range and for P{sub miss} < 310 MeV#18;c. The {sub 16}O(#7;e,#4;e'p)#8; cross section was measured in the dip region at q = 1026 MeV and #2; {omega} = 586#12;#15;#19;#2; MeV for 10 MeV <#3; E{sub miss} < 320 MeV. This thesis presents the results for the missing energy continuum (#7;E{sub miss}>25#4; #3;#15; MeV)#8; from this experiment.
Date: February 1, 1999
Creator: Liyanage, Nilanga
Partner: UNT Libraries Government Documents Department

ANGULAR MOMENTUM MISALIGNMENT IN DEEP INELASTIC PROCESSES AND ANGULAR DISTRIBUTION OF SEQUENTIALLY EMITTED PARTICLES AND GAMMA RAYS

Description: The angular momentum misalignment for fragments produced in deep inelastic scattering is discussed in terms of the thermal excitation of angular-momentum-bearing modes in the intermediate complex. Analytical expressions for the in- and out-of-plane angular distributions are obtained for sequentially emitted particles and fission fragments. The angular momentum dependence of the ratio between particle and neutron decay width is explicitly treated and found to be quite important. Similarly angular distributions are obtained both for dipole and quadrupole gamma decay. The theoretical results are compared with experimental angular distributions of sequential fission fragments, sequential alphas and gamma rays and a good agreement is found.
Date: December 1, 1980
Creator: Moretto, L.G.; Blau, S. & Pacheco, A.
Partner: UNT Libraries Government Documents Department

SEARCH FOR QUARK EFFECTS IN THE d+{sup 4}He SYSTEM

Description: It has been suggested that bags containing more than three interacting quarks may be formed in high energy collisions; these states would appear as narrow reasonances in the inelastic channels. We have measured the inclusive cross section d+ {sup 4}He{yields}p+X at E{sub cm} =6.25 to 7.91 GeV in steps of 50 to 100 MeV to search for a eighteen quark bag resonance. Upper limits on the production cross section are presented.
Date: March 1, 1980
Creator: McClelland, J.B.; Carroll, J.B.; Igo, G.J.; Oostens, J.; Brochard, F.; Perez-Mendez, V. et al.
Partner: UNT Libraries Government Documents Department

UPPER LIMITS FOR BOUND STATES AND RESONANCE BEHAVIOR IN THE TRINEUTRON SYSTEM

Description: The trineutron mass spectrum was observed in the stopped pion radiative capture reaction {sup 3}H({pi}{sup -},{gamma})3n by measuring the photon energy with a high resolution spectrometer. The present experiment improves upon an earlier experiment by a factor of 27 in statistics and 2.2 in resolution. An improved upper limit (95% confidence level) on the branching ratio (bound state)/(total radiative capture rate) is found to be 4 X 10{sup -3}. No resonant structure is observed beyond that predicted by the pairwise interaction of the outgoing nucleons. The upper limit on the branching ratio to resonances with {Gamma} {&lt;=} 5 MeV is 2 X 10{sup -2}. 1
Date: March 1, 1980
Creator: Miller, J.P.
Partner: UNT Libraries Government Documents Department

Polarized {sup 3}He(e,e'n) Asymmetries in Three Orthogonal Measurements

Description: Asymmetry measurements were conducted in Jefferson Lab's experimental Hall A through electron scattering from a polarized {sup 3}He target in the quasi-elastic polarized-{sup 3}He(e,e'n) reaction. Measurements were made with the target polarized in the longitudinal direction with respect to the incoming electrons A_L, in a transverse direction that was orthogonal to the beam-line and parallel to the q-vector A_T, and in a vertical direction that was orthogonal to both the beam-line and the q-vector (A_y^0). The experiment measured $A_y^0$ at four-momentum transfer squared Q^2 of 0.127 (GeV/c)^2, 0.456 (GeV/c)^2, and 0.953 (GeV/c)^2. The A_T and A_L asymmetries were both measured at Q^2 of 0.505 (GeV/c)^2 and 0.953 (GeV/c)^2. This is the first time that three orthogonal asymmetries have been measured simultaneously. Results from this experiment are compared with the plane wave impulse approximation (PWIA) and Faddeev calculations. These results provide important tests of models that use 3He as an effective neutron target and show that the PWIA holds above Q^2 of 0.953 (GeV/c)^2.
Date: September 1, 2012
Creator: Long, Elena
Partner: UNT Libraries Government Documents Department

Improvements to Nuclear Data and Its Uncertainties by Theoretical Modeling

Description: This project addresses three important gaps in existing evaluated nuclear data libraries that represent a significant hindrance against highly advanced modeling and simulation capabilities for the Advanced Fuel Cycle Initiative (AFCI). This project will: Develop advanced theoretical tools to compute prompt fission neutrons and gamma-ray characteristics well beyond average spectra and multiplicity, and produce new evaluated files of U and Pu isotopes, along with some minor actinides; Perform state-of-the-art fission cross-section modeling and calculations using global and microscopic model input parameters, leading to truly predictive fission cross-sections capabilities. Consistent calculations for a suite of Pu isotopes will be performed; Implement innovative data assimilation tools, which will reflect the nuclear data evaluation process much more accurately, and lead to a new generation of uncertainty quantification files. New covariance matrices will be obtained for Pu isotopes and compared to existing ones. The deployment of a fleet of safe and efficient advanced reactors that minimize radiotoxic waste and are proliferation-resistant is a clear and ambitious goal of AFCI. While in the past the design, construction and operation of a reactor were supported through empirical trials, this new phase in nuclear energy production is expected to rely heavily on advanced modeling and simulation capabilities. To be truly successful, a program for advanced simulations of innovative reactors will have to develop advanced multi-physics capabilities, to be run on massively parallel super- computers, and to incorporate adequate and precise underlying physics. And all these areas have to be developed simultaneously to achieve those ambitious goals. Of particular interest are reliable fission cross-section uncertainty estimates (including important correlations) and evaluations of prompt fission neutrons and gamma-ray spectra and uncertainties.
Date: February 18, 2013
Creator: Danon, Yaron; Nazarewicz, Witold & Talou, Patrick
Partner: UNT Libraries Government Documents Department

Building A Universal Nuclear Energy Density Functional (UNEDF)

Description: During the period of Dec. 1 2006 – Jun. 30, 2012, the UNEDF collaboration carried out a comprehensive study of all nuclei, based on the most accurate knowledge of the strong nuclear interaction, the most reliable theoretical approaches, the most advanced algorithms, and extensive computational resources, with a view towards scaling to the petaflop platforms and beyond. The long-term vision initiated with UNEDF is to arrive at a comprehensive, quantitative, and unified description of nuclei and their reactions, grounded in the fundamental interactions between the constituent nucleons. We seek to replace current phenomenological models of nuclear structure and reactions with a well-founded microscopic theory that delivers maximum predictive power with well-quantified uncertainties. Specifically, the mission of this project has been three-fold: first, to find an optimal energy density functional (EDF) using all our knowledge of the nucleonic Hamiltonian and basic nuclear properties; second, to apply the EDF theory and its extensions to validate the functional using all the available relevant nuclear structure and reaction data; third, to apply the validated theory to properties of interest that cannot be measured, in particular the properties needed for reaction theory. The main physics areas of UNEDF, defined at the beginning of the project, were: ab initio structure; ab initio functionals; DFT applications; DFT extensions; reactions.
Date: September 30, 2012
Creator: Carlson, Joe, Los Alamos National Laboratory, Los Alamos, NM; Furnstahl, Dick, Ohio State University, Columbus, OH; Horoi, Mihai, Central Michigan University, Mount Pleasant, MI; Lusk, Rusty, Argonne National Laboratory, Argonne, IL; Nazarewicz, Witek, University of Tennessee, Knoxville, TN; Ng, Esmond, Berkeley National Laboratory, Berkeley, CA et al.
Partner: UNT Libraries Government Documents Department

BUILDING A UNIVERSAL NUCLEAR ENERGY DENSITY FUNCTIONAL (UNEDF)

Description: The long-term vision initiated with UNEDF is to arrive at a comprehensive, quantitative, and unified description of nuclei and their reactions, grounded in the fundamental interactions between the constituent nucleons. We seek to replace current phenomenological models of nuclear structure and reactions with a well-founded microscopic theory that delivers maximum predictive power with well-quantified uncertainties. Specifically, the mission of this project has been three-fold: First, to find an optimal energy density functional (EDF) using all our knowledge of the nucleonic Hamiltonian and basic nuclear properties. Second, to apply the EDF theory and its extensions to validate the functional using all the available relevant nuclear structure and reaction data. Third, to apply the validated theory to properties of interest that cannot be measured, in particular the properties needed for reaction theory.
Date: July 1, 2012
Creator: Nazarewicz, Witold
Partner: UNT Libraries Government Documents Department

Energy Transfer by Neutrons to Certain Materials

Description: What is attempted here is to compute the energy absorbed in several elements from interactions with neutrons in the energy range of 0 to 14 Mev. In these calculations the results have been normalized to one neutron per square centimeter incident per gram of target material, thus making it a simpler matter to calculate energy absorbed in compounds containing these elements. In these calculations the single-collision approximation is assumed in that each neutron is considered to undergo only one collision in the sample, that scattered neutron escaping from the sample. The results are presented graphically for the elements hydrogen, carbon, nitrogen; oxygen: ·aluminum, ·silicon, germanium, tantalum, and bismuth. Plotted in these figures is the energy transferred per gram of target material per single neutron per square centimeter incident as a function of the-incident neutron energy.
Date: July 1, 1965
Creator: Buckalew, W. H.
Partner: UNT Libraries Government Documents Department

The Suppression of Energy Discretization Errors in Multigroup Transport Calculations

Description: The Objective of this project is to develop, implement, and test new deterministric methods to solve, as efficiently as possible, multigroup neutron transport problems having an extremely large number of groups. Our approach was to (i) use the standard CMFD method to "coarsen" the space-angle grid, yielding a multigroup diffusion equation, and (ii) use a new multigrid-in-space-and-energy technique to efficiently solve the multigroup diffusion problem. The overall strategy of (i) how to coarsen the spatial and energy grids, and (ii) how to navigate through the various grids, has the goal of minimizing the overall computational effort. This approach yields not only the fine-grid solution, but also coarse-group flux-weighted cross sections that can be used for other related problems.
Date: June 17, 2013
Creator: Larsen, Edward
Partner: UNT Libraries Government Documents Department

CONCERNING TESTS OF TIME REVERSAL INVARIANCE VIA THE POLARIZATION-ANALYZING POWER EQUALITY

Description: It is shown that one of the more recent tests of time reversal invariance, via measurements of the polarization and the analyzing power in p + {sup 13}C elastic scattering, does not, in fact, provide a significant test of time reversal invariance. This follows from the fact that the polarization-analyzing power equality depends on the equality of the two possible spin~flip probabilities. A possible non-zero difference between the spin-flip was beyond the precision of the experiment because the individual spin-flip probabilities are so small. It is immediately clear that tests of time reversal invariance should be made through measurements of the polarization and analyzing power in a reaction (and its inverse) where the spin-flip probability is expected or known to be large.
Date: June 1, 1980
Creator: Conzett, Homer E.
Partner: UNT Libraries Government Documents Department