Timelike Virtual Compton Scattering from Electron-Positron Radiative Annihilation (open access)

Timelike Virtual Compton Scattering from Electron-Positron Radiative Annihilation

We propose measurements of the deeply virtual Compton amplitude (DVCS) {gamma}* {yields} H{bar H}{gamma} in the timelike t = (p{sub H} + p{sub {bar H}}){sup 2} > 0 kinematic domain which is accessible at electron-positron colliders via the radiative annihilation process e{sup +}e{sup -} {yields} H{bar H}{gamma}. These processes allow the measurement of timelike deeply virtual Compton scattering for a variety of H{bar H} hadron pairs such as {pi}{sup +}{pi}{sup -}, K{sup +}K{sup -}, and D{bar D} as well as p{bar p}. As in the conventional spacelike DVCS, there are interfering coherent amplitudes contributing to the timelike processes involving C = - form factors. The interference between the amplitudes measures the phase of the C = + timelike DVCS amplitude relative to the phase of the timelike form factors and can be isolated by considering the forward-backward e{sup +} {leftrightarrow} e{sup -} asymmetry. The J = 0 fixed pole contribution which arises from the local coupling of the two photons to the quark current plays a special role. As an example we present a simple model.
Date: March 31, 2009
Creator: Afanasev, Andrei; Brodsky, Stanley J.; Carlson, Carl E. & Mukherjee, Asmita
System: The UNT Digital Library
A broadband high-resolution elliptical crystal x-ray spectrometer for high energy density physics experiments (open access)

A broadband high-resolution elliptical crystal x-ray spectrometer for high energy density physics experiments

Spectroscopic investigation of high temperature laser produced plasmas in general, and x-ray opacity experiments in particular, often requires instruments with both a broad coverage of x-ray energies and high spectral, spatial, and temporal resolution. We analyze the design, model the response, and report the commissioning of a spectrometer using elliptical crystals in conjunction with a large format, gated microchannel plate detector. Measurements taken with this instrument at the JANUS laser facilities demonstrate the designed spectral range of 0.24 to 5.8 keV, and spectral resolution E/{Delta}E > 500, resulting in 2 to 3 times more spectral data than achieved by previous spectrometer designs. The observed 100 picosecond temporal resolution and 35 {micro}m spatial resolution are consistent with the requirements of high energy density opacity experiments.
Date: March 31, 2006
Creator: Anderson, S G; Heeter, R F; Booth, R; Emig, J; Fulkerson, S; McCarville, T et al.
System: The UNT Digital Library
Deducing the 237U destruction cross-sections using the Surrogate Ratio Method (open access)

Deducing the 237U destruction cross-sections using the Surrogate Ratio Method

We have deduced the destruction cross section of {sup 237}U via the (n, {gamma}) and (n,2n) reactions over an equivalent neutron energy range of 0 to 20 MeV using a new form of the Surrogate Ratio method [1-4] . The relative fission and neutron-evaporation decay probabilities of excited {sup 238}U populated via the ({alpha},{alpha}{prime}) inelastic scattering were measured using the silicon telescope array for reaction studies (STARS) coupled to the Livermore Berkeley array for collaborative experiments (LIBERACE). These relative probabilities were then combined with the {sup 237} U(n,f) cross section deduced by Burke et al., [4] to deduce the (n, {gamma}) and (n,2n) cross sections in a model independent fashion. These cross sections are then compared to the compound reaction cross section calculated using an optical model calculation tuned to reproduce scattering data in the transactinide region. Our results presented and the prospects for using this technique to deduce (n,x) cross sections on radioactive nuclei are discussed.
Date: March 31, 2006
Creator: Bernstein, L. A.; Burke, J. T.; Ahle, L.; Church, J. A.; Escher, J.; Dietrich, F. S. et al.
System: The UNT Digital Library
Proposal for a High Energy Nuclear Database (open access)

Proposal for a High Energy Nuclear Database

The authors propose to develop a high-energy heavy-ion experimental database and make it accessible to the scientific community through an on-line interface. This database will be searchable and cross-indexed with relevant publications, including published detector descriptions. Since this database will be a community resource, it requires the high-energy nuclear physics community's financial and manpower support. This database should eventually contain all published data from Bevalac, AGS and SPS to RHIC and CERN-LHC energies, proton-proton to nucleus-nucleus collisions as well as other relevant systems, and all measured observables. Such a database would have tremendous scientific payoff as it makes systematic studies easier and allows simpler benchmarking of theoretical models to a broad range of old and new experiments. Furthermore, there is a growing need for compilations of high-energy nuclear data for applications including stockpile stewardship, technology development for inertial confinement fusion and target and source development for upcoming facilities such as the Next Linear Collider. To enhance the utility of this database, they propose periodically performing evaluations of the data and summarizing the results in topical reviews.
Date: March 31, 2005
Creator: Brown, D. A. & Vogt, R.
System: The UNT Digital Library
Proposal for a High Energy Nuclear Database (open access)

Proposal for a High Energy Nuclear Database

We propose to develop a high-energy heavy-ion experimental database and make it accessible to the scientific community through an on-line interface. This database will be searchable and cross-indexed with relevant publications, including published detector descriptions. Since this database will be a community resource, it requires the high-energy nuclear physics community's financial and manpower support. This database should eventually contain all published data from Bevalac and AGS to RHIC to CERN-LHC energies, proton-proton to nucleus-nucleus collisions as well as other relevant systems, and all measured observables. Such a database would have tremendous scientific payoff as it makes systematic studies easier and allows simpler benchmarking of theoretical models to a broad range of old and new experiments. Furthermore, there is a growing need for compilations of high-energy nuclear data for applications including stockpile stewardship, technology development for inertial confinement fusion and target and source development for upcoming facilities such as the Next Linear Collider. To enhance the utility of this database, we propose periodically performing evaluations of the data and summarizing the results in topical reviews.
Date: March 31, 2005
Creator: Brown, David A. & Vogt, Ramona
System: The UNT Digital Library
Commissioning of a Higher Harmonic RF System for the Advanced Light Source (open access)

Commissioning of a Higher Harmonic RF System for the Advanced Light Source

We report on the commissioning of a higher harmonic RF system designed to improve the Touschek lifetime of the Advanced Light Source. In our best results, we have achieved over a factor of two increase in the beam lifetime. Transient beam loading of the harmonic cavities by unequal fill patterns presents the greatest limitations on lifetime improvement. We also describe several interesting effects of the harmonic cavities on the operation of the longitudinal and transverse multibunch feedback systems.
Date: March 31, 2000
Creator: Byrd, John M.; De Santis, Stefano; Georgsson, Mattias; Stover,G.; Fox, John D. & Teytelman, Dmitry
System: The UNT Digital Library
Very high power THz radiation at Jefferson Lab (open access)

Very high power THz radiation at Jefferson Lab

We report the production of high power (20 watts average, {approx};1 Megawatt peak) broadband THz light based on coherent emission from relativistic electrons. We describe the source, presenting theoretical calculations and their experimental verification. For clarity we compare this source with one based on ultrafast laser techniques, and in fact the radiation has qualities closely analogous to that produced by such sources, namely that it is spatially coherent, and comprises short duration pulses with transform-limited spectral content. In contrast to conventional THz radiation, however, the intensity is many orders of magnitude greater due to the relativistic enhancement.
Date: March 31, 2002
Creator: Carr, G. L.; Martin, Michael C.; McKinney, Wayne R.; Jordan, K.; Neil, George R. & Williams, G. P.
System: The UNT Digital Library
Exact Lattice Supersymmetry (open access)

Exact Lattice Supersymmetry

We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of N = 4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.
Date: March 31, 2009
Creator: Catterall, Simon; Kaplan, David B. & Unsal, Mithat
System: The UNT Digital Library
Development of computer program ENMASK for prediction of residual environmental masking-noise spectra, from any three independent environmental parameters (open access)

Development of computer program ENMASK for prediction of residual environmental masking-noise spectra, from any three independent environmental parameters

Residual environmental sound can mask intrusive4 (unwanted) sound. It is a factor that can affect noise impacts and must be considered both in noise-impact studies and in noise-mitigation designs. Models for quantitative prediction of sensation level (audibility) and psychological effects of intrusive noise require an input with 1/3 octave-band spectral resolution of environmental masking noise. However, the majority of published residual environmental masking-noise data are given with either octave-band frequency resolution or only single A-weighted decibel values. A model has been developed that enables estimation of 1/3 octave-band residual environmental masking-noise spectra and relates certain environmental parameters to A-weighted sound level. This model provides a correlation among three environmental conditions: measured residual A-weighted sound-pressure level, proximity to a major roadway, and population density. Cited field-study data were used to compute the most probable 1/3 octave-band sound-pressure spectrum corresponding to any selected one of these three inputs. In turn, such spectra can be used as an input to models for prediction of noise impacts. This paper discusses specific algorithms included in the newly developed computer program ENMASK. In addition, the relative audibility of the environmental masking-noise spectra at different A-weighted sound levels is discussed, which is determined by using the methodology …
Date: March 31, 2000
Creator: Chang, Y.-S.; Liebich, R. E. & Chun, K. C.
System: The UNT Digital Library
Testing LaMgAl11O19 crystal for X-ray spectroscopy (open access)

Testing LaMgAl11O19 crystal for X-ray spectroscopy

We investigated the properties of the rare earth crystal LaMgAl{sub 11}O{sub 19} and its application to soft X-ray spectroscopy. Its relative reflectivity and half width rocking curve were measured to up to the reflection order of 28. In addition, a comparative measurement of the iron L-shell soft X-ray line emission was made on the EBIT-I Livermore electron beam ion trap by fielding the LaMgAl{sub 11}O{sub 19} crystal side by side with a rubidium hydrogen phthalate crystal in a flat crystal spectrometer. From these measurements, reflectivity and spectral resolving power were determined.
Date: March 31, 2004
Creator: Chen, H.; Beiersdorfer, P.; Baronova, E.; Kalashnikova, I. & Stepanenko, M.
System: The UNT Digital Library
Publication and Protection of Sensitive Site Information in a Grid Infrastructure (open access)

Publication and Protection of Sensitive Site Information in a Grid Infrastructure

In order to create a successful grid infrastructure, sites and resource providers must be able to publish information about their underlying resources and services. This information makes it easier for users and virtual organizations to make intelligent decisions about resource selection and scheduling, and can be used by the grid infrastructure for accounting and troubleshooting services. However, such an outbound stream may include data deemed sensitive by a resource-providing site, exposing potential security vulnerabilities or private user information to the world at large, including malicious entities. This study analyzes the various vectors of information being published from sites to grid infrastructures. In particular, it examines the data being published to, and collected by the Open Science Grid, including resource selection, monitoring, accounting, troubleshooting, logging and site verification data. We analyze the risks and potential threat models posed by the publication and collection of such data. We also offer some recommendations and best practices for sites and grid infrastructures to manage and protect sensitive data.
Date: March 31, 2008
Creator: Cholia, Shreyas; Cholia, Shreyas & Porter, R. Jefferson
System: The UNT Digital Library
Transgenic Medicago truncatula plants obtained from Agrobacterium tumefaciens-transformed roots and Agrobacterium rhizogenes-transformed hairy roots (open access)

Transgenic Medicago truncatula plants obtained from Agrobacterium tumefaciens-transformed roots and Agrobacterium rhizogenes-transformed hairy roots

Article on transgenic Medicago truncatula plants obtained from Agrobacterium tumefaciens-transformed roots and Agrobacterium rhizogenes-transformed hairy roots.
Date: January 9, 2006
Creator: Crane, Cynthia; Wright, Elane; Dixon, R. A. & Wang, Z.-Y. (Zeng-Yu), 1963-
System: The UNT Digital Library
Gauge Theories on an Interval: Unitarity Without a HiggsBoson (open access)

Gauge Theories on an Interval: Unitarity Without a HiggsBoson

None
Date: March 31, 2004
Creator: Csaki, Csaba; Grojean, Christophe; Murayama, Hitoshi; Luigi,Pilo & Terning, John
System: The UNT Digital Library
Mixing Effects on the Precipitation and Cross Flows Filtration of a Hanford Simulated Precipitated Radioactive Waste (open access)

Mixing Effects on the Precipitation and Cross Flows Filtration of a Hanford Simulated Precipitated Radioactive Waste

As part of the River Protection Project at Hanford, Washington, Bechtel National, Inc. has been contracted by the United States Department of Energy to design a Waste Treatment and Immobilization Plant to stabilize liquid radioactive waste. Because of its experience with radioactive waste stabilization, the Savannah River Technology Center of the Westinghouse Savannah River Company is working with Bechtel National and Washington Group International, to help design and test certain parts of the Waste Treatment Plant. One part of the process is the separation of radioactive isotopes from the liquid waste by a precipitation reaction and cross-flow ultrafiltration. To better understand those combined processes an experiment was performed using a simulated radioactive waste, made to prototypically represent the chemical and physical characteristics of a Hanford waste in tank 241-AN-102 and precipitated under prototypic conditions. The resultant slurry was then filtered using a cross-flow filter prototypic in porosity, length, and diameter to the plant design. An important aspect of filtration for waste treatment is the rate at which permeate is produced. There are many factors that affect filtration rate and one of the most difficult to obtain is the effect of particles in the waste streams. The Waste Treatment Plant will …
Date: March 31, 2004
Creator: DUIGNAN, MARK
System: The UNT Digital Library
Thermodynamics of the Complexation of Uranium(VI) by oxalate in aqueous solution at 10-70oC (open access)

Thermodynamics of the Complexation of Uranium(VI) by oxalate in aqueous solution at 10-70oC

The protonation reactions of oxalate (ox) and the complex formation of uranium(VI) with oxalate in 1.05 mol kg{sup -1} NaClO{sub 4} were studied at variable temperatures (10-70 C). Three U(VI)/ox complexes (UO{sub 2}ox{sub j}{sup (2-2j){sup +}} with j = 1, 2, 3) were identified in this temperature range. The formation constants and the molar enthalpies of complexation were determined by spectrophotometry and calorimetry. The complexation of uranium(VI) with oxalate ion is exothermic at lower temperatures (10-40 C) and becomes endothermic at higher temperatures (55-70 C). In spite of this, the free energy of complexation becomes more negative at higher temperatures due to increasingly more positive entropy of complexation that exceeds the increase of the enthalpy of complexation. The thermodynamic parameters at different temperatures, in conjunction with the literature data for other dicarboxylic acids, provide insight into the relative strength of U(VI) complexes with a series of dicarboxylic acids (oxalic, malonic and oxydiacetic) and rationalization for the highest stability of U(VI)/oxalate complexes in the series. The data reported in this study are of importance in predicting the migration of uranium(VI) in geological environments in the case of failure of the engineering barriers which protect waste repositories.
Date: March 31, 2009
Creator: Di Bernardo, Plinio; Zanonato, Pier Luigi; Tian, Guoxin; Tolazzi, Marilena & Rao, Linfeng
System: The UNT Digital Library
SYMMETRY, HAMILTONIAN PROBLEMS AND WAVELETS IN ACCELERATOR PHYSICS (open access)

SYMMETRY, HAMILTONIAN PROBLEMS AND WAVELETS IN ACCELERATOR PHYSICS

In this paper the authors consider applications of methods from wavelet analysis to nonlinear dynamical problems related to accelerator physics. In this approach they take into account underlying algebraical, geometrical and topological structures of corresponding problems.
Date: March 31, 2000
Creator: FEDOROVA,A.; ZEITLIN,M. & PARSA,Z.
System: The UNT Digital Library
VARIATIONAL APPROACH IN WAVELET FRAMEWORK TO POLYNOMIAL APPROXIMATIONS OF NONLINEAR ACCELERATOR PROBLEMS (open access)

VARIATIONAL APPROACH IN WAVELET FRAMEWORK TO POLYNOMIAL APPROXIMATIONS OF NONLINEAR ACCELERATOR PROBLEMS

In this paper the authors present applications of methods from wavelet analysis to polynomial approximations for a number of accelerator physics problems. According to a variational approach in the general case they have the solution as a multiresolution (multiscales) expansion on the base of compactly supported wavelet basis. They give an extension of their results to the cases of periodic orbital particle motion and arbitrary variable coefficients. Then they consider more flexible variational method which is based on a biorthogonal wavelet approach. Also they consider a different variational approach, which is applied to each scale.
Date: March 31, 2000
Creator: FEDOROVA,A.; ZEITLIN,M. & PARSA,Z.
System: The UNT Digital Library
El Nino - La Nina Implications on Flood Hazard Mitigation (open access)

El Nino - La Nina Implications on Flood Hazard Mitigation

The effects of El Nino and La Nina periods on the maximum daily winter period depths of precipitation are examined using records from five precipitation gages on the Nevada Test Site. The potential implications of these effects are discussed.
Date: March 31, 2006
Creator: French, R. & Miller, J.
System: The UNT Digital Library
2008 Photoions, Photoionization & Photodetachment Gordon Research Conference January 27-February 1, 2008 (open access)

2008 Photoions, Photoionization & Photodetachment Gordon Research Conference January 27-February 1, 2008

This conference brings together scientists interested in a range of basic phenomena linked to the ejection and scattering of electrons from atoms, molecules, clusters, liquids and solids by absorption of light. Photoionization, a highly sensitive probe of both structure and dynamics, can range from perturbative single-photon processes to strong-field highly non-perturbative interactions. It is responsible for the formation and destruction of molecules in astrophysical and plasma environments and successfully used in advanced analytical techniques. Positive ions, which can be produced and studied most effectively using photoionization, are the major components of all plasmas, vital constituents of flames and important intermediates in many chemical reactions. Negative ions are significant as transient species and, when photodetached, the corresponding neutral species often undergoes remarkable, otherwise non-observable, dynamics. The scope of the meeting spans from novel observations in atomic and molecular physics, such as Coulomb Crystals, highly excited states and cold Rydberg plasmas, to novel energy resolved or ultrafast time-resolved experiments, photoionization in strong laser fields, theoretical method development for electron scattering, photoionization and photodetachment and more complex phenomena such as charge transfer and DNA and protein conductivity, important for biological and analytical applications.
Date: March 31, 2009
Creator: GRay, Klaus Muller-Dethefs Nancy Ryan
System: The UNT Digital Library
Relating D0-anti-D0 Mixing and D0 -> l l- with New Physics (open access)

Relating D0-anti-D0 Mixing and D0 -> l l- with New Physics

We point out how, in certain models of New Physics, the same combination of couplings occurs in the amplitudes for both D{sup 0}-{bar D}{sup 0} mixing and the rare decays D{sup 0} {yields} {ell}{sup +}{ell}{sup -}. If the New Physics dominates and is responsible for the observed mixing, then a very simple correlation exists between the magnitudes of each; in fact the rates for the decay D{sup 0} {yields} {ell}{sup +}{ell}{sup -} are completely fixed by the mixing. Observation of D{sup 0} {yields} {ell}{sup +}{ell}{sup -} in excess of the Standard Model prediction could identify New Physics contributions to D{sup 0}-{bar D}{sup 0} mixing.
Date: March 31, 2009
Creator: Golowich, Eugene; Hewett, JoAnne; Pakvasa, Sandip & Petrov, Alexey A.
System: The UNT Digital Library
Evolving Dark Energy with w =/ -1 (open access)

Evolving Dark Energy with w =/ -1

Theories of evolving quintessence are constructed that generically lead to deviations from the w = -1 prediction of non-evolving dark energy. The small mass scale that governs evolution, m_\phi \approx 10^-33 eV, is radiatively stable, and the"Why Now?'' problem is solved. These results rest crucially on seesaw cosmology: in broad outline, fundamental physics and cosmology can be understood from only two mass scales, the weak scale, v, and the Planck scale, M. Requiring a scale of dark energy \rho_DE^1/4 governed by v^2/M, and a radiatively stable evolution rate m_\phi given by v^4/M^3, leads to a distinctive form for the equation of state w(z) that follows from a cosine quintessence potential. An explicit hidden axion model is constructed. Dark energy resides in the potential of the axion field which is generated by a new QCD-like force that gets strong at the scale \Lambda \approx v^2/M \approx \rho_DE^1/4. The evolution rate is given by a second seesaw that leads to the axion mass, m_\phi \approx \Lambda^2/f, with f \approx M.
Date: March 31, 2005
Creator: Hall, Lawrence J.; Nomura, Yasunori & Oliver, Steven J.
System: The UNT Digital Library
Ceramic Coatings for Corrosion Resistant Nuclear Waste Container Evaluated in Simulated Ground Water at 90?C (open access)

Ceramic Coatings for Corrosion Resistant Nuclear Waste Container Evaluated in Simulated Ground Water at 90?C

Ceramic materials have been considered as corrosion resistant coatings for nuclear waste containers. Their suitability can be derived from the fully oxidized state for selected metal oxides. Several types of ceramic coatings applied to plain carbon steel substrates by thermal spray techniques have been exposed to 90 C simulated ground water for nearly 6 years. In some cases no apparent macroscopic damage such as coating spallation was observed in coatings. Thermal spray processes examined in this work included plasma spray, High Velocity Oxy Fuel (HVOF), and Detonation Gun. Some thermal spray coatings have demonstrated superior corrosion protection for the plain carbon steel substrate. In particular the HVOF and Detonation Gun thermal spray processes produced coatings with low connected porosity, which limited the growth rate of corrosion products. It was also demonstrated that these coatings resisted spallation of the coating even when an intentional flaw (which allowed for corrosion of the carbon steel substrate underneath the ceramic coating) was placed in the coating. A model for prediction of the corrosion protection provided by ceramic coatings is presented. The model includes the effect of the morphology and amount of the porosity within the thermal spray coating and provides a prediction of the …
Date: March 31, 2004
Creator: Haslam, J J & Farmer, J C
System: The UNT Digital Library
Integrated analysis of breast cancer cell lines reveals unique signaling pathways (open access)

Integrated analysis of breast cancer cell lines reveals unique signaling pathways

Cancer is a heterogeneous disease resulting from the accumulation of genetic defects that negatively impact control of cell division, motility, adhesion and apoptosis. Deregulation in signaling along the EGFR-MAPK pathway is common in breast cancer, though the manner in which deregulation occurs varies between both individuals and cancer subtypes. We were interested in identifying subnetworks within the EGFR-MAPK pathway that are similarly deregulated across subsets of breast cancers. To that end, we mapped genomic, transcriptional and proteomic profiles for 30 breast cancer cell lines onto a curated Pathway Logic symbolic systems model of EGFR-MEK signaling. This model was comprised of 539 molecular states and 396 rules governing signaling between active states. We analyzed these models and identified several subtype specific subnetworks, including one that suggested PAK1 is particularly important in regulating the MAPK cascade when it is over-expressed. We hypothesized that PAK1 overexpressing cell lines would have increased sensitivity to MEK inhibitors. We tested this experimentally by measuring quantitative responses of 20 breast cancer cell lines to three MEK inhibitors. We found that PAK1 over-expressing luminal breast cancer cell lines are significantly more sensitive to MEK inhibition as compared to those that express PAK1 at low levels. This indicates that …
Date: March 31, 2009
Creator: Heiser, Laura M.; Wang, Nicholas J.; Talcott, Carolyn L.; Laderoute, Keith R.; Knapp, Merrill; Guan, Yinghui et al.
System: The UNT Digital Library
Comparison of ALINGAAS/GAAS Superlattice Photocathodes Having Low Conduction Band Offset (open access)

Comparison of ALINGAAS/GAAS Superlattice Photocathodes Having Low Conduction Band Offset

The main advantage of superlattice (SL) structures as spin polarized electron emitters is the ability to provide a large splitting between the heavy hole (HH) and light hole (LH) valence bands (VB) over a large active thickness compared to single strained layers. Two important depolarization mechanisms in these structures are the scattering effects during the transit of the electrons in the active region and the depolarization that takes place in the band bending region (BBR) near the surface. In this paper, we systematically study the effects of the electron mobility and transit time by using an InAlGaAs/GaAs SL with a flat conduction band (CB). Initial results by the SPTU-SLAC collaboration using such structures grown by the Ioffe Institute showed polarization and quantum yield (QE) of 92% and 0.2% respectively. We report measurements using similar structures grown by SVT Associates. The results (polarization up to 90%) are also compared with simulations.
Date: March 31, 2006
Creator: Ioakeimidi, K.; Maruyama, T.; Clendenin, J. E.; Brachmann, A.; Garwin, E. L.; Kirby, R. E. et al.
System: The UNT Digital Library