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Observation of a New D_s Meson Decaying to D K at a Mass of 2.86 GeV/c^2 (open access)

Observation of a New D_s Meson Decaying to D K at a Mass of 2.86 GeV/c^2

The authors observe a new D{sub s} meson with mass (2856.6 {+-} 1.5{sub stat.} {+-} 5.0{sub syst.}) MeV/c{sup 2} and width (48 {+-} 7{sub stat.} {+-} 10{sub syst.}) MeV/c{sup 2} decaying into D{sup 0}K{sup +} and D{sup +}K{sub S}{sup 0}. In the same mass distributions they also observe a broad structure with mass (2688 {+-} 4{sub stat.} {+-} 3{sub syst.}) MeV/c{sup 2} and width (112 {+-} 7{sub stat.} {+-} 36{sub syst.}) MeV/c{sup 2}. To obtain this result they use 240 fb{sup -1} of data recorded by the BABAR detector at the PEP-II asymmetric e{sup +}e{sup -} storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.
Date: October 4, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Optical Absorption, Stability and Structure of NpO2+ Complexeswith Dicarboxylic Acids (open access)

Optical Absorption, Stability and Structure of NpO2+ Complexeswith Dicarboxylic Acids

Complexation of NpO2+ with oxalic acid (OX),2,2'-oxydiacetic acid (ODA), 2,2'-iminodiacetic acid (IDA) and 2,2'-thiodiacetic acid (TDA), has been studied using spectrophotometry in1 M NaClO4. Both the position and the intensity of the absorption band of NpO2+ at 980 nm are affected by the formation of NpO2+/dicarboxylate complexes, providing useful information on the complexation strength, the coordination mode and the structure of the complexes.
Date: January 4, 2006
Creator: Tian, Guoxin & Rao, Linfeng
System: The UNT Digital Library
Protonation of D-gluconate and its complexation with Np(V) inacidic to nearly neutral solutions (open access)

Protonation of D-gluconate and its complexation with Np(V) inacidic to nearly neutral solutions

None
Date: January 4, 2006
Creator: Zhang, Zhicheng; Clark, Sue B.; Tian, Guoxin; Zanonato,PierLuigi & Rao, Linfeng
System: The UNT Digital Library
A sampling-based Bayesian model for gas saturation estimationusing seismic AVA and marine CSEM data (open access)

A sampling-based Bayesian model for gas saturation estimationusing seismic AVA and marine CSEM data

We develop a sampling-based Bayesian model to jointly invertseismic amplitude versus angles (AVA) and marine controlled-sourceelectromagnetic (CSEM) data for layered reservoir models. The porosityand fluid saturation in each layer of the reservoir, the seismic P- andS-wave velocity and density in the layers below and above the reservoir,and the electrical conductivity of the overburden are considered asrandom variables. Pre-stack seismic AVA data in a selected time windowand real and quadrature components of the recorded electrical field areconsidered as data. We use Markov chain Monte Carlo (MCMC) samplingmethods to obtain a large number of samples from the joint posteriordistribution function. Using those samples, we obtain not only estimatesof each unknown variable, but also its uncertainty information. Thedeveloped method is applied to both synthetic and field data to explorethe combined use of seismic AVA and EM data for gas saturationestimation. Results show that the developed method is effective for jointinversion, and the incorporation of CSEM data reduces uncertainty influid saturation estimation, when compared to results from inversion ofAVA data only.
Date: April 4, 2006
Creator: Chen, Jinsong; Hoversten, Michael; Vasco, Don; Rubin, Yoram & Hou,Zhangshuan
System: The UNT Digital Library
Scaling laws for collisionless laser-plasma interactions of relevance for laboratory astrophysics (open access)

Scaling laws for collisionless laser-plasma interactions of relevance for laboratory astrophysics

Scaling laws for interaction of ultra-intense laser beams with a collisionless plasmas are discussed. Special attention is paid to the problem of the collective ion acceleration. Symmetry arguments in application to the generation of the poloidal magnetic field are presented. A heuristic model for evaluating the magnetic field strength is proposed.
Date: April 4, 2006
Creator: Ryutov, D. D. & Rermington, B. A.
System: The UNT Digital Library
Search for Small Trans-Neptunian Objects by the TAOS Project (open access)

Search for Small Trans-Neptunian Objects by the TAOS Project

The Taiwan-America Occultation Survey (TAOS) aims to determine the number of small icy bodies in the outer reach of the Solar System by means of stellar occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9) telescopes have been installed at Lulin Observatory in Taiwan to simultaneously monitor some thousand of stars for such rare occultation events. Because a typical occultation event by a TNO a few km across will last for only a fraction of a second, fast photometry is necessary. A special CCD readout scheme has been devised to allow for stellar photometry taken a few times per second. Effective analysis pipelines have been developed to process stellar light curves and to correlate any possible flux changes among all telescopes. A few billion photometric measurements have been collected since the routine survey began in early 2005. Our preliminary result of a very low detection rate suggests a deficit of small TNOs down to a few km size, consistent with the extrapolation of some recent studies of larger (30-100 km) TNOs.
Date: December 4, 2006
Creator: Chen, Wen-Ping; Alcock, C.; Axelrod, T.; Bianco, F. B.; Byun, Y. I.; Chang, Y. H. et al.
System: The UNT Digital Library
Secondary Neutron-Production Cross Sections from Heavy-IonInteractions between 230 and 600 MeV/nucleon (open access)

Secondary Neutron-Production Cross Sections from Heavy-IonInteractions between 230 and 600 MeV/nucleon

Secondary neutron-production cross-sections have beenmeasured from interactions of 230 MeV/nucleon He, 400 MeV/nucleon N, 400MeV/nucleon Kr, 400 MeV/nucleon Xe, 500 MeV/nucleon Fe, and 600MeV/nucleon Ne interacting in a variety of elemental and compositetargets. We report the double-differential production cross sections,angular distributions, energy spectra, and total cross sections from allsystems. Neutron energies were measured using the time-of-flighttechnique, and were measured at laboratory angles between 5 deg and 80deg. The spectra exhibit behavior previously reported in otherheavy-ion-induced neutron production experiments; namely, a peak atforward angles near the energy corresponding to the beam velocity, withthe remaining spectra generated by preequilibrium and equilibriumprocesses. The double-differential spectra are fitted with amoving-source parameterization. Observations on the dependence of thetotal cross sections on target and projectile mass arediscussed.
Date: October 4, 2006
Creator: Heilbronn, L.H.; Zeitlin, C.J.; Iwata, Y.; Murakami, T.; Iwase,H.; Nakamura, T. et al.
System: The UNT Digital Library
Self-Consistent Simulations of Heavy-Ion Beams Interacting with Electron-Clouds (open access)

Self-Consistent Simulations of Heavy-Ion Beams Interacting with Electron-Clouds

Electron-clouds and rising desorbed gas pressure limit the performance of many existing accelerators and, potentially, that of future accelerators including heavy-ion warm-dense matter and fusion drivers. For the latter, self-consistent simulation of the interaction of the heavy-ion beam(s) with the electron-cloud is necessary. To this end, we have merged the two codes WARP (HIF accelerator code) and POSINST (high-energy e-cloud build-up code), and added modules for neutral gas molecule generation, gas ionization, and electron tracking algorithms in magnetic fields with large time steps. The new tool is being benchmarked against the High-Current Experiment (HCX) and good agreement has been achieved. The simulations have also aided diagnostic interpretation and have identified unanticipated physical processes. We present the ''roadmap'' describing the different modules and their interconnections, along with detailed comparisons with HCX experimental results, as well as a preliminary application to the modeling of electron clouds in the Large Hadron Collider.
Date: August 4, 2006
Creator: Vay, J; Furman, M A; Seidl, P A; Cohen, R H; Friedman, A; Grote, D P et al.
System: The UNT Digital Library
Spacetime thermodynamics and subsystem observables in akinetically constrained model of glassy systems (open access)

Spacetime thermodynamics and subsystem observables in akinetically constrained model of glassy systems

In a recent article it was argued that dynamic heterogeneity in d-dimensional glass formers is a manifestation of an order-disorder phenomenon in the d+1 dimensions of spacetime. By considering a dynamical analogue of the free energy, evidence was found for phase coexistence between active and inactive regions of spacetime, and it was suggested that this phenomenon underlies the glass transition. Here we develop these ideas further by investigating in detail the one-dimensional Fredrickson-Andersen (FA) model in which the active and inactive phases originate in the reducibility of the dynamics. We illustrate the phase coexistence by considering the distributions of mesoscopic spacetime observables. We show how the analogy with phase coexistence can be strengthened by breaking microscopic reversibility in the FA model, leading to a non-equilibrium theory in the directed percolation universality class.
Date: October 4, 2006
Creator: Jack, Robert L.; Garrahan, Juan P. & Chandler, David
System: The UNT Digital Library
Structure of incommensurate gold sulfide monolayer on Au(111) (open access)

Structure of incommensurate gold sulfide monolayer on Au(111)

Two-dimensional confined systems, such as substrate-supported incommensurate layers, are of interest because their structural and electronic properties may differ from those of bulk materials. While advances in experimental techniques have resulted in the growth of many such interesting systems, progress can often be hampered by the lack of an atomistic-scale understanding of the structure, especially for incommensurate systems. In this work, we develop an atomic-scale model for an ordered incommensurate gold-sulfide (AuS) adlayer that has been previously demonstrated to exist on the Au(111) surface, following sulfur deposition and annealing to 450 K. We introduce theoretical techniques within density functional theory to take into account charge transfer in an incommensurate system and model scanning tunneling microscopy images, which are in good agreement with experiment. Our simulations indicate that this model is remarkably robust. We analyze the nature of bonding in this structure using state-of-the-art Wannier-function based techniques. Our analysis provides a natural explanation for the extraordinary robustness and unusual stoichiometry of this layer. This structure and its chemistry have implications for related S-Au interfaces, such as those in self-assembled monolayers of thiols on Au substrates.
Date: October 4, 2006
Creator: Quek, S Y; Biener, M M; Biener, J; Bhattacharjee, J; Friend, C M; Waghmare, U V et al.
System: The UNT Digital Library
Thomson scattering techniques in laser produced plasmas (open access)

Thomson scattering techniques in laser produced plasmas

Thomson scattering has been shown to be a valuable technique for measuring the plasma conditions in laser produced plasmas. Measurement techniques are discussed that use the ion-acoustic frequency measured from the collective Thomson-scattering spectrum to extract the electron temperature, ion temperature, plasma flow, and electron density in a laser produced plasma. In a recent study, they demonstrated a novel Thomson-scattering technique to measure the dispersion of ion-acoustic fluctuations that employing multiple color Thomson-scattering diagnostics. They obtained frequency-resolved Thomson-scattering spectra of the two separate thermal ion-acoustic fluctuations with significantly different wave vectors. This new technique allows a simultaneous time resolved local measurement of electron density and temperature. The plasma fluctuations are shown to become dispersive with increasing electron temperature. Furthermore, a Thomson-scattering technique to measure the electron temperature profile is presented where recent experiments have measured a large electron temperature gradient (Te = 1.4 keV to Te = 3.2 keV over 1.5-mm) along the axis of a 2-mm long hohlraum when heated asymmetrically.
Date: May 4, 2006
Creator: Froula, D. H.; Ross, J. S.; Divol, L.; MacKinnon, A. J.; Sorce, C. & Glenzer, S. H.
System: The UNT Digital Library
Time-resolved Soft X-Ray Imaging (SXRI) diagnostic for use at the NIF and OMEGA lasers (open access)

Time-resolved Soft X-Ray Imaging (SXRI) diagnostic for use at the NIF and OMEGA lasers

The soft x-ray imager (SXRI) built for the first experiments at the National Ignition Facility (NIF) has four soft x-ray channels and one hard x-ray channel. The SXRI is a snout that mounts to a four strip gated imager. This produces four soft x-ray images per strip, which can be separated in time by {approx}60psec. Each soft x-ray channel consists of a mirror plus a filter. The diagnostic was used to study x-ray burnthrough of hot hohlraum targets at the NIF and OMEGA lasers. The SXRI snout design and issues involved in selecting the desired soft x-ray channels are discussed.
Date: May 4, 2006
Creator: Schneider, M; Holder, J; James, D; Bruns, H; Celeste, J; Compton, S et al.
System: The UNT Digital Library
TWO-PHASE FLOW STUDIES IN NUCLEAR POWER PLANT PRIMARY CIRCUITS USING THE THREE-DIMENSIONAL THERMAL-HYDRAULIC CODE BAGIRA. (open access)

TWO-PHASE FLOW STUDIES IN NUCLEAR POWER PLANT PRIMARY CIRCUITS USING THE THREE-DIMENSIONAL THERMAL-HYDRAULIC CODE BAGIRA.

In this paper we present recent results of the application of the thermal-hydraulic code BAGIRA to the analysis of complex two-phase flows in nuclear power plants primary loops. In particular, we performed benchmark numerical simulation of an integral LOCA experiment performed on a test facility modeling the primary circuit of VVER-1000. In addition, we have also analyzed the flow patterns in the VVER-1000 steam generator vessel for stationary and transient operation regimes. For both of these experiments we have compared the numerical results with measured data. Finally, we demonstrate the capabilities of BAGIRA by modeling a hypothetical severe accident for a VVER-1000 type nuclear reactor. The numerical analysis, which modeled all stages of the hypothetical severe accident up to the complete ablation of the reactor cavity bottom, shows the importance of multi-dimensional flow effects.
Date: June 4, 2006
Creator: KOHURT, P. (BNL), KALINICHENKO, S.D.; KROSHILIN, A.E.; KROSHILIN, V.E. & SMIRNOV, A.V.
System: The UNT Digital Library
UCLA/FNPL Underdense Plasma Lens Experiment: Results and Analysis (open access)

UCLA/FNPL Underdense Plasma Lens Experiment: Results and Analysis

Focusing of a 15 MeV, 16 nC electron bunch by a gaussian underdense plasma lens operated just beyond the threshold of the underdense condition has been demonstrated. The strong 1.9 cm focal length plasma lens focused both transverse directions simultaneously and reduced the minimum area of the beam spot by a factor of 23. Analysis of the beam envelope evolution observed near the beam waist shows that the spherical aberrations of this underdense lens are lower than those of an overdense plasma lens, as predicted by theory. Time resolved measurements of the focused electron bunch are also reported and compared to simulations.
Date: August 4, 2006
Creator: Thompson, M C; Badakov, H; Rosenzweig, J B; Travish, G; Fliller, R; Kazakevich, G M et al.
System: The UNT Digital Library
Ultra-High Gradient Dielectric Wakefield Accelerator Experiments (open access)

Ultra-High Gradient Dielectric Wakefield Accelerator Experiments

Ultra-high gradient dielectric wakefield accelerators are a potential option for a linear collider afterburner since they are immune to the ion collapse and electron/positron asymmetry problems implicit in a plasma based afterburner. The first phase of an experiment to study the performance of dielectric Cerenkov wakefield accelerating structures at extremely high gradients in the GV/m range has been completed. The experiment took advantage of the unique SLAC FFTB electron beam and its ultra-short pulse lengths and high currents (e.g., {sigma}{sub z} = 20 {micro}m at Q = 3 nC). The FFTB electron beam was successfully focused down and sent through short lengths of fused silica capillary tubing (ID = 200 {micro}m/OD = 325 {micro}m). The pulse length of the electron beam was varied to produce a range of electric fields between 2 and 20 GV/m at the inner surface of the dielectric tubes. We observed a sharp increase in optical emissions from the capillaries in the middle part of this surface field range which we believe indicates the transition between sustainable field levels and breakdown. If this initial interpretation is correct, the surfaced fields that were sustained equate to on axis accelerating field of several GV/m. In future experiments being …
Date: August 4, 2006
Creator: Thompson, M. C.; Badakov, H.; Rosenzweig, J. B.; Travish, G.; Hogan, M.; Ischebeck, R. et al.
System: The UNT Digital Library
A Universe Without Weak Interactions (open access)

A Universe Without Weak Interactions

None
Date: April 4, 2006
Creator: Harnik, Roni; Kribs, Graham D. & Perez, Gilad
System: The UNT Digital Library
Word Domain Disambiguation via Word Sense Disambiguation (open access)

Word Domain Disambiguation via Word Sense Disambiguation

Word subject domains have been widely used to improve the perform-ance of word sense disambiguation al-gorithms. However, comparatively little effort has been devoted so far to the disambiguation of word subject do-mains. The few existing approaches have focused on the development of al-gorithms specific to word domain dis-ambiguation. In this paper we explore an alternative approach where word domain disambiguation is achieved via word sense disambiguation. Our study shows that this approach yields very strong results, suggesting that word domain disambiguation can be ad-dressed in terms of word sense disam-biguation with no need for special purpose algorithms.
Date: June 4, 2006
Creator: Sanfilippo, Antonio P.; Tratz, Stephen C. & Gregory, Michelle L.
System: The UNT Digital Library
X-ray Pulse Length Characterization using the Surface Magneto Optic Kerr Effect (open access)

X-ray Pulse Length Characterization using the Surface Magneto Optic Kerr Effect

It will be challenging to measure the temporal profile of the hard X-ray SASE beam independently from the electron beam in the LCLS and other 4th generation light sources. A fast interaction mechanism is needed that can be probed by an ultrafast laser pulse in a pump-probe experiment. It is proposed to exploit the rotation in polarization of light reflected from a thin magnetized film, known as the surface magneto optic Kerr effect (SMOKE), to witness the absorption of the x-ray pulse in the thin film. The change in spin orbit coupling induced by the x-ray pulse occurs on the subfemtosecond time scale and changes the polarization of the probe beam. The limitation to the technique lies with the bandwidth of the probe laser pulse and how short the optical pulse can be made. The SMOKE mechanism will be described and the choices of materials for use with 1.5 {angstrom} x-rays. A schematic description of the pump-probe geometry for x-ray diagnosis is also described.
Date: October 4, 2006
Creator: Krejcik, P.
System: The UNT Digital Library