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Electroproduction of Photons and of Pawns on the Proton in Quadrimoment of Transfer Q2=1.0GeV2. Measure Cross Sections and Extraction of Polarizabilities Generalities; Electroproduction de Photons et de Pions sur le Proton au Quadrimoment de Transfert Q2=1.0GeV2. Mesure des Sections Efficaces et Extraction des Polarisabilites Generalisees

Description: In hadronic physics, the nucleon structure and the quarks confinement are still topical issues. The neutral pion electroproduction and virtual Compton scattering (VCS) reactions allow us to access new observables that describe this structure. This work is focused on the VCS experiment performed at Jefferson Lab in 1998.
Date: November 6, 2001
Creator: Laveissiere, Geraud
Partner: UNT Libraries Government Documents Department

Static hybrid quarkonium potential with improved staggered quarks

Description: The authors are studying the effects of light dynamical quarks on the excitation energies of a flux tube between a static quark and antiquark. They report preliminary results of an analysis of the ground state potential and the {Sigma}{prime}{sub g}{sup +} and II{sub u} potentials. They have measured these potentials on closely matched ensembles of gauge configurations, generated in the quenched approximation and with 2+1 flavors of Asqtad improved staggered quarks.
Date: January 6, 2004
Creator: al., C. Bernard et
Partner: UNT Libraries Government Documents Department

Confinement Studies of Auxiliary Heated NSTX Plasmas

Description: The confinement of auxiliary heated NSTX discharges is discussed. The energy confinement time in plasmas with either L-mode or H-mode edges is enhanced over the values given by the ITER97L and ITER98Pby(2) scalings, being up to 2-3 times L-mode and 1.5 times H-mode. TRANSP calculations based on the kinetic profile measurements reproduce the magnetics-based determination of stored energy and the measured neutron production rate. Power balance calculations reveal that, in a high power neutral beam heated H-mode discharge, the ion thermal transport is near neoclassical levels, and well below the electron thermal transport, which is the main loss channel. Perturbative impurity injection techniques indicate the particle diffusivity to be slightly above the neoclassical level in discharges with L-mode edge. High-harmonic fast-wave (HHFW) bulk electron heating is described and thermal transport is discussed. Thermal ion transport is found to be above neoclassical level, but thermal electron transport remains the main loss mechanism. Evidences of an electron thermal internal transport barrier obtained with HHFW heating are presented. A description of H-mode discharges obtained during HHFW heating is presented.
Date: May 6, 2003
Creator: LeBlanc, B.P.; Bell, M.G.; Bell, R.E.; Bitter, M.L.; Bourdelle, C.; Gates, D.A. et al.
Partner: UNT Libraries Government Documents Department

Recent results using all point quark propagators

Description: Pseudofermion methods for extracting all-point quark propagators are reviewed, with special emphasis on techniques for reducing or eliminating autocorrelations induced by low eigenmodes of the quark Dirac operator. Recent applications, including high statistics evaluations of hadronic current correlators and the pion form factor, are also described.
Date: January 6, 2004
Creator: Duncan, A. & Yoo, E. Eichten and J.
Partner: UNT Libraries Government Documents Department

Monsanto Chemical Company, Unit 3 abstracts of progress reports, August 16--31, 1945: Summary of work to date on volatile neutron source

Description: It was proposed to prepare a volatile polonium compound which could be used alone or with another gaseous compound as a neutron source. The objective was to obtain a neutron source which would give off few neutrons in the expanded state, but when condensed would act substantially as a thick target and emit perhaps ten times as many neutrons. Originally, polonium hexafluoride was suggested; with such compound the fluorine atoms would constitute the target. the predicted boiling point of polonium hexafluoride is about -40 {degrees}C. There was reason to believe, however, that lower relatively non-volatile fluorides would be formed rather than the hexafluoride. Polonium alkyls were therefore proposed as alternatives. The predicted boiling point of Po(CH{sub 3}){sub 2} is about 110 {degrees}C. This compound in itself would probably not be suitable as a target material but it could be mixed with other gases such as carbon tetrafluoride, boron trifluoride, etc., as targets. As a longer range possibility, Po(CF{sub 3}){sub 2} was also suggested. This compound would act as its own target and would moreover have the same F/Po ratio as PoF{sub 6}; its boiling point could be expected to be 30{degrees} - 60 {degrees} lower than that of polonium dimethyl. Calculations were made with showed that the desired effect could be obtained either with Po F{sub 6} or with a mixture of Po(CH{sub 3}){sub 2} with a suitable target gas. Investigation of the preparation of these two compounds was therefore undertaken, and later some preliminary attempts to prepare polonium carbonyl were made.
Date: September 6, 1945
Creator: Rollinson, C.L.
Partner: UNT Libraries Government Documents Department

Preliminary results for two pion resonances in D{sup +} and D{sup +}{sub s} {r_arrow} {pi}{sup {minus}}{pi}{sup +}{pi}{sup +} from Fermilab experiment E-791

Description: In this paper the authors present preliminary results of a coherent amplitude analysis of three-pion decays of charm mesons. The analysis includes a greater number of possible resonant states than in previous analyses, and produces masses and Breit-Wigner widths of the isoscalar resonances f{sub 0} (980) and f{sub 0} (1370) with better precision than previous measurements. They also present preliminary results for the mass and width of the low lying f{sub o} (400), sometimes called the {sigma} meson.
Date: July 6, 2000
Creator: Stefanski, Raymond J.
Partner: UNT Libraries Government Documents Department

Vacancy Clusters at Nanoparticle Surfaces

Description: The authors detect vacancy clusters at Au nanoparticle surfaces using a combination of positron lifetime spectroscopy, 1- detector, and 2-detector measurements of Doppler broadening of annihilation radiation. Gold nanoparticles are formed by MeV implantation of gold ions into MgO (100) followed by annealing. Clusters of two Mg and two O vacancies (v{sub 4}) are attached to the gold nanoparticle surfaces within the projected range (R{sub p}).
Date: August 6, 2000
Creator: Xu, J.; Moxom, J.; Somieski, B.; White, C.W.; Mills, A.P.; Suzuki, R. et al.
Partner: UNT Libraries Government Documents Department


Description: A compilation is made of the various ways in which quantum phenomena enter into the design and operation of a neutrino factory. They include production of pions, decay of pions into muons, ionization energy loss of muons in material, scattering and energy straggling of muons in material, polarization of muons, and the decay of muons into neutrinos, and the radiation effect of neutrinos. For each process formulas are presented which cover the basic mechanism. A discussion is presented of the areas of uncertainty and of the experiments, underway and proposed, which will reduce the uncertainty to an acceptable level.
Date: December 6, 2000
Partner: UNT Libraries Government Documents Department

Photometry of SN 2002ic and implications for the progenitor mass-loss history

Description: We present new pre-maximum and late-time optical photometry of the Type Ia/IIn supernova 2002ic. These observations are combined with the published V-band magnitudes of Hamuy et al. (2003) and the VLT spectrophotometry of Wang et al. (2004) to construct the most extensive light curve to date of this unusual supernova. The observed flux at late time is significantly higher relative to the flux at maximum than that of any other observed Type Ia supernova and continues to fade very slowly a year after explosion. Our analysis of the light curve suggests that a non-Type Ia supernova component becomes prominent {approx}20 days after explosion. Modeling of the non-Type Ia supernova component as heating from the shock interaction of the supernova ejecta with pre-existing circumstellar material suggests the presence of a {approx}1.7 x 1015 cm gap or trough between the progenitor system and the surrounding circumstellar material. This gap could be due to significantly lower mass-loss {approx}15 (nu{sub omega}/10 km/s) -1 years prior to explosion or evacuation of the circumstellar material by a low-density fast wind. The latter is consistent with observed properties of proto-planetary nebulae and with models of white-dwarf + asymptotic giant branch star progenitor systems with the asymptotic giant branch star in the proto-planetary nebula phase.
Date: May 6, 2004
Creator: Wood-Vasey, W.M.; Wang, L. & Aldering, G.
Partner: UNT Libraries Government Documents Department


Description: As part of its commitment to clean up Cold War legacy sites, the U.S. Department of Energy (DOE) has initiated an exciting and unique project to dispose of its inventory of uranium-233 (233U) stored at Oak Ridge National Laboratory (ORNL), and extract isotopes that show great promise in the treatment of deadly cancers. In addition to increasing the supply of potentially useful medical isotopes, the project will rid DOE of a nuclear concern and cut surveillance and security costs. For more than 30 years, DOE's ORNL has stored over 1,200 containers of fissile 233U, originally produced for several defense-related projects, including a pilot study that looked at using 233U as a commercial reactor fuel. This uranium, designated as special nuclear material, requires expensive security, safety, and environmental controls. It has been stored at an ORNL facility, Building 3019A, that dates back to the Manhattan Project. Down-blending the material to a safer form, rather than continuing to store it, will eliminate a $15 million a year financial liability for the DOE and increase the supply of medical isotopes by 5,700 percent. During the down-blending process, thorium-229 (229Th) will be extracted. The thorium will then be used to extract actinium-225 (225Ac), which will ultimately supply its progeny, bismuth-213 (213Bi), for on-going cancer research. The research includes Phase II clinical trials for the treatment of acute myelogenous leukemia at Sloan-Kettering Memorial Cancer Center in New York, as well as other serious cancers of the lungs, pancreas, and kidneys using a technique known as alpha-particle radioimmunotherapy. Alpha-particle radioimmunotherapy is based on the emission of alpha particles by radionuclides. 213Bi is attached to a monoclonal antibody that targets specific cells. The bismuth then delivers a high-powered but short-range radiation dose, effectively killing the cancerous cells but sparing the surrounding tissue. Production of the actinium and ...
Date: October 6, 2004
Creator: Nicholas, R.G.; Lacy, N.H.; Butz, T.R. & Brandon, N.E.
Partner: UNT Libraries Government Documents Department

Azimuthally sensitive hanbury brown-twiss interferometry in Au + Au collisions sqrt S sub NN = 200 GeV

Description: We present the results of a systematic study of the shape of the pion distribution in coordinate space at freeze-out in Au+Au collisions at RHIC using two-pion Hanbury Brown-Twiss (HBT) interferometry. Oscillations of the extracted HBT radii vs. emission angle indicate sources elongated perpendicular to the reaction plane. The results indicate that the pressure and expansion time of the collision system are not sufficient to completely quench its initial shape.
Date: June 6, 2004
Creator: Argonne National Laboratory
Partner: UNT Libraries Government Documents Department

(Strange) meson interferometry at RHIC

Description: The authors make predictions for the kaon interferometry measurements in Au + Au collisions at the relativistic Heavy Ion Collider (RHIC). A first order phase transition from a thermalized Quark-Gluon-Plasma (QGP) to a gas of hadrons is assumed for the transport calculations. The fraction of kaons that are directly emitted from the phase boundary is considerably enhanced at large transverse momenta K{sub T} {approx} 1 GeV/c. In this kinematic region, the sensitivity of the R{sub out}/R{sub side} ratio to the QGP-properties is enlarged. The results of the 1-dimensional correlation analysis are presented. The extracted interferometry radii, depending on K{sub T}, are not unusually large and are strongly affected by finite momentum resolution effects.
Date: February 6, 2002
Creator: Soff, Sven; Bass, Steffen A.; Hardtke, David H. & Panitkin, Sergey Y.
Partner: UNT Libraries Government Documents Department

Energetic Ion Transport and Concomitant Change of the Fusion Reactivity during Reconnection Events in Spherical Tori

Description: Effects of MHD reconnection events on the beam-plasma fusion reactivity and transport of the beam ions are studied. Based on the analysis of fusion reactivity changes induced by MHD events, the conclusion is drawn that the strong drops of the neutron yield during sawtooth crashes observed in the National Spherical Torus experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] are associated with both a particle redistribution inside the plasma and a loss of the beam ions. Mechanisms of the energetic ion transport during sawtooth crashes are analyzed, in particular, with the use of the resonance adiabatic invariant derived in this paper. A numerical simulation of the particle motion during a sawtooth crash in NSTX is done with the code OFSEF [Ya. I. Kolesnichenko, et al., Nucl. Fusion 40, 1325 (2000)] extended for a better description of the particle precession. It is shown that the motion of toroidally passing particles in NSTX can become stochastic under the influence of a crash. This stochasticity, as well as the motion along the resonance island, leads to the escape of some particles from the plasma.
Date: July 6, 2004
Creator: Kolesnichenko, Ya.I.; Lutsenko, V.V.; White, R.B. & Yakovenko, Yu.V.
Partner: UNT Libraries Government Documents Department

A transport-based condensed history algorithm

Description: Condensed history algorithms are approximate electron transport Monte Carlo methods in which the cumulative effects of multiple collisions are modeled in a single step of (user-specified) path length s{sub 0}. This path length is the distance each Monte Carlo electron travels between collisions. Current condensed history techniques utilize a splitting routine over the range 0 {le} s {le} s{sub 0}. For example, the PEnELOPE method splits each step into two substeps; one with length {xi}s{sub 0} and one with length (1 {minus}{xi})s{sub 0}, where {xi} is a random number from 0 < {xi} < 1. because s{sub 0} is fixed (not sampled from an exponential distribution), conventional condensed history schemes are not transport processes. Here the authors describe a new condensed history algorithm that is a transport process. The method simulates a transport equation that approximates the exact Boltzmann equation. The new transport equation has a larger mean free path than, and preserves two angular moments of, the Boltzmann equation. Thus, the new process is solved more efficiently by Monte Carlo, and it conserves both particles and scattering power.
Date: January 6, 1999
Creator: Tolar Jr, D R
Partner: UNT Libraries Government Documents Department

Topological susceptibility with the improved Asqtad action

Description: As a test of the chiral properties of the improved Asqtad (staggered fermion) action, we have been measuring the topological susceptibility as a function of quark masses for 2 + 1 dynamical flavors. We report preliminary results, which show reasonable agreement with leading order chiral perturbation theory for lattice spacing less than 0.1 fm. The total topological charge, however, shows strong persistence over Monte Carlo time.
Date: January 6, 2004
Creator: al., C. Bernard et
Partner: UNT Libraries Government Documents Department


Description: Results on physics at RHIC using outgoing leptons and photons will be presented from Au+Au collisions at nucleon-nucleon c.m. energies {radical}(sNN) = 130 GeV and 200 GeV, and from p-p collisions at {radical}(sNN) = 200 GeV. Introduction and motivation will be presented both from the theoretical and experimental perspectives. Topics include open charm production via single e{sup {+-}}, J/{Psi} {yields} e{sup +} + e{sup -}, {mu}{sup +} + {mu}{sup -} and inclusive photon production.
Date: January 6, 2003
Partner: UNT Libraries Government Documents Department

Fast Neutral Pressure Measurements in NSTX

Description: Several fast neutral pressure gauges have been installed on NSTX [National Spherical Torus Experiment] to measure the vessel and divertor pressure during inductive and coaxial helicity injected (CHI) plasma operations. Modified, PDX [Poloidal Divertor Experiment]-type Penning gauges have been installed on the upper and lower divertors. Neutral pressure measurements during plasma operations from these and from two shielded fast Micro ion gauges at different toroidal locations on the vessel mid-plane are described. A new unshielded ion gauge, referred to as the In-vessel Neutral Pressure (INP) gauge is under development.
Date: August 6, 2002
Creator: Raman, R.; Kugel, H.W.; Provost, T.; Gernhardt, R.; Jarboe, T.R. & Bell, M.G.
Partner: UNT Libraries Government Documents Department


Description: In these lectures, the authors develop the theory of the Colour Glass Condensate. This is the matter made of gluons in the high density environment characteristic of deep inelastic scattering or hadron-hadron collisions at very high energy. The lectures are self contained and comprehensive. They start with a phenomenological introduction, develop the theory of classical gluon fields appropriate for the Colour Glass, and end with a derivation and discussion of the renormalization group equations which determine this effective theory.
Date: August 6, 2001
Partner: UNT Libraries Government Documents Department

Polarized parton distributions and the polarized gluon asymmetry.

Description: The flavor-dependent valence, sea quark and antiquark spin distributions can be determined separately from theoretical assumptions and experimental data. The authors have determined the valence distributions using the Bjorken sum rule and have extracted polarized sea distributions, assuming that the quarks and anti-quarks for each flavor are symmetric. Other experiments have been proposed which will allow them to completely break the SU(3) symmetry of the sea flavors. To create a physical model for the polarized gluons, they investigate the gluon spin asymmetry in a proton, A{sub G}(x,Q{sup 2}) = {Delta}G(x,Q{sup 2})/G(x,Q{sup 2}). By assuming that this is approximately Q{sup 2} invariant, they can completely determine the x-dependence of this asymmetry, which satisfies constituent counting rules and reproduces the basic results of the Bremsstrahlung model originated by Close and Sivers. This asymmetry can be combined with the measured unpolarized gluon density, G(x,Q{sup 2}) to provide a prediction for {Delta}G(x,Q{sup 2}). Existing and proposed experiments can test both the prediction of scale-invariance for A{sub G}(x,Q{sup 2}) and the nature of {Delta}G itself. These models can be discussed along with suggestions for specific experiments which can be performed at energies typical of HERA, RHIC and LHC to determine these polarized distributions.
Date: February 6, 2002
Creator: Ramsey, G. P.
Partner: UNT Libraries Government Documents Department

Octupole effects at super and normal deformation.

Description: This presentation deals with recent results on the onset of octupole collectivity in superdeformed nuclei of the A {approx} 190 and A {approx} 150 regions as well as in actinide nuclei at normal deformation. It is shown that most of the properties of these negative parity sequences can be understood in terms of Random Phase Approximation (RPA) calculations, although the observations in some Pu isotopes continue to be a challenge to interpret.
Date: June 6, 2002
Creator: Janssens, R. V. F.
Partner: UNT Libraries Government Documents Department

The Potential of Fast Ignition and Related Experiments with A Petawatt Laser Facility

Description: A model of energy gain induced by fast ignition of thermonuclear burn in compressed deuterium-tritium fuel, is used to show the potential for 300x gain with a driver energy of 1 M J, if the National Ignition Facility (NIF) were to be adapted for fast ignition. The physics of fast ignition has been studied using a petawatt laser facility at the Lawrence Livermore National Laboratory. Laser plasma interaction in a preformed plasma on a solid target leads to relativistic self-focusing evidenced by x-ray images. Absorption of the laser radiation transfers energy to an intense source of relativistic electrons. Good conversion efficiency into a wide angular distribution is reported. Heating by the electrons in solid density CD{sub 2} produces 0.5 to 1/keV temperature, inferred from the D-D thermo-nuclear neutron yield.
Date: April 6, 2000
Creator: Key, M.H.; Campbell, E.M.; Cowan, T.E.; Hatchett, S.P.; Henry, E.A.; Koch, J.A. et al.
Partner: UNT Libraries Government Documents Department