1,363 Matching Results

Search Results


Description: Recent strong experimental evidence of a narrow exotic S = +1 baryon resonance, {Theta}{sup +}, suggests the existence of other exotic baryons. We discuss the prospects of confirming earlier experimental evidence of {Theta}{sup +} and the observation of additional hypothetical exotic baryons in e{sup +}e{sup -} annihilations and {gamma}{gamma} collisions at LEP and B Factories.
Date: June 28, 2004
Partner: UNT Libraries Government Documents Department

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

Description: The Large Hadron Collider (LHC) at CERN promises a major step forward in the understanding of the fundamental nature of matter. The ATLAS experiment is a general-purpose detector for the LHC, whose design was guided by the need to accommodate the wide spectrum of possible physics signatures. The major remit of the ATLAS experiment is the exploration of the TeV mass scale where groundbreaking discoveries are expected. In the focus are the investigation of the electroweak symmetry breaking and linked to this the search for the Higgs boson as well as the search for Physics beyond the Standard Model. In this report a detailed examination of the expected performance of the ATLAS detector is provided, with a major aim being to investigate the experimental sensitivity to a wide range of measurements and potential observations of new physical processes. An earlier summary of the expected capabilities of ATLAS was compiled in 1999 [1]. A survey of physics capabilities of the CMS detector was published in [2]. The design of the ATLAS detector has now been finalised, and its construction and installation have been completed [3]. An extensive test-beam programme was undertaken. Furthermore, the simulation and reconstruction software code and frameworks have been completely rewritten. Revisions incorporated reflect improved detector modelling as well as major technical changes to the software technology. Greatly improved understanding of calibration and alignment techniques, and their practical impact on performance, is now in place. The studies reported here are based on full simulations of the ATLAS detector response. A variety of event generators were employed. The simulation and reconstruction of these large event samples thus provided an important operational test of the new ATLAS software system. In addition, the processing was distributed world-wide over the ATLAS Grid facilities and hence provided an important test of the ATLAS ...
Date: November 28, 2011
Creator: Aad, G.; Abat, E.; Abbott, B.; Abdallah, J.; Abdelalim, A. A.; Abdesselam, A. et al.
Partner: UNT Libraries Government Documents Department

Discovery of TeV Gamma-Ray Emission from the Cygnus Region

Description: The diffuse gamma radiation arising from the interaction of cosmic ray particles with matter and radiation in the Galaxy is one of the few probes available to study the origin of the cosmic rays. Milagro is a water Cherenkov detector that continuously views the entire overhead sky. The large field-of-view combined with the long observation time makes Milagro the most sensitive instrument available for the study of large, low surface brightness sources such as the diffuse gamma radiation arising from interactions of cosmic radiation with interstellar matter. In this paper we present spatial and flux measurements of TeV gamma-ray emission from the Cygnus Region. The TeV image shows at least one new source MGRO J2019+37 as well as correlations with the matter density in the region as would be expected from cosmic-ray proton interactions. However, the TeV gamma-ray flux as measured at {approx}12 TeV from the Cygnus region (after excluding MGRO J2019+37) exceeds that predicted from a conventional model of cosmic ray production and propagation. This observation indicates the existence of either hard-spectrum cosmic-ray sources and/or other sources of TeV gamma rays in the region.
Date: November 28, 2006
Creator: Abdo, A.A.; Allen, B.; Berley, D.; Blaufuss, E.; Casanova, S.; Chen, C. et al.
Partner: UNT Libraries Government Documents Department

Up-to-date p-p Interaction Modeling and Secondarygamma, e+/- and Neutrino Spectra in Astronomical Environment

Description: We have calculated spectra of stable secondary particles ({gamma}, e{sup {+-}}, {nu}{sub e}, {bar {nu}}{sub e}, {nu}{sub {mu}}{bar {nu}}{sub {mu}}) produced in high energy p-p interactions in astrophysical environment. The calculation has incorporated the up-to-date rising inelastic cross-sections, the diffraction dissociation process, and the Feynman scaling violation for the first time. We then found that the diffractive process makes secondary particle spectra harder than that of the incident proton; that the rising inelastic cross-section and the scaling violation produces significantly more secondary particles than previous calculations. Combination of the three features explain about a half of the ''GeV Excess'' in the EGRET Galactic diffuse {gamma}-ray spectrum with the local cosmic proton spectrum (power-law index around 2.7). The excess can be fully explained if the proton spectral index in the Galactic ridge is harder by 0.2 than above. As an extension of the calculation, we have parameterized the inclusive secondary particle spectra as functions of the incident proton kinetic energy: we predict {approx} 30% more e{sup +} and {nu}{sub e} than e{sup -} and {bar {nu}}{sub e} to be produced in the GeV range by p-p interactions.
Date: June 28, 2005
Creator: Abe, T.; Kamae, T.; Karlsson, N.; Koi, T.; Mizuno, T. & /SLAC
Partner: UNT Libraries Government Documents Department

Practical Thermal Evaluation Methods For HAC Fire Analysis In Type B Radiaoactive Material (RAM) Packages

Description: Title 10 of the United States Code of Federal Regulations Part 71 for the Nuclear Regulatory Commission (10 CFR Part 71.73) requires that Type B radioactive material (RAM) packages satisfy certain Hypothetical Accident Conditions (HAC) thermal design requirements to ensure package safety during accidental fire conditions. Compliance with thermal design requirements can be met by prototype tests, analyses only or a combination of tests and analyses. Normally, it is impractical to meet all the HAC using tests only and the analytical methods are too complex due to the multi-physics non-linear nature of the fire event. Therefore, a combination of tests and thermal analyses methods using commercial heat transfer software are used to meet the necessary design requirements. The authors, along with his other colleagues at Savannah River National Laboratory in Aiken, SC, USA, have successfully used this 'tests and analyses' approach in the design and certification of several United States' DOE/NNSA certified packages, e.g. 9975, 9977, 9978, 9979, H1700, and Bulk Tritium Shipping Package (BTSP). This paper will describe these methods and it is hoped that the RAM Type B package designers and analysts can use them for their applications.
Date: March 28, 2013
Creator: Abramczyk, Glenn; Hensel, Stephen J & Gupta, Narendra K.
Partner: UNT Libraries Government Documents Department

Focused Ion Beam Induced Effects on MOS Transistor Parameters

Description: We report on recent studies of the effects of 50 keV focused ion beam (FIB) exposure on MOS transistors. We demonstrate that the changes in value of transistor parameters (such as threshold voltage, V{sub t}) are essentially the same for exposure to a Ga+ ion beam at 30 and 50 keV under the same exposure conditions. We characterize the effects of FIB exposure on test transistors fabricated in both 0.5 {micro}m and 0.225 {micro}m technologies from two different vendors. We report on the effectiveness of overlying metal layers in screening MOS transistors from FIB-induced damage and examine the importance of ion dose rate and the physical dimensions of the exposed area.
Date: July 28, 1999
Creator: Abramo, Marsha T.; Antoniou, Nicholas; Campbell, Ann N.; Fleetwood, Daniel M.; Hembree, Charles E.; Jessing, Jeffrey R. et al.
Partner: UNT Libraries Government Documents Department

IUPAC-NIST Solubility Data Series. 98. Solubility of Polycyclic Aromatic Hydrocarbons in Pure and Organic Solvent Mixtures: Revised and Updated. Part 1. Binary Solvent Mixtures

Description: Article on the solubility of polycyclic aromatic hydrocarbons in pure and organic solvent mixtures. This work updates volumes 54, 58, and 59 in the IUPAC Solubility Data Series and presents solubility data for polycyclic aromatic hydrocarbon solutes dissolved in binary organic solvent mixtures.
Date: February 28, 2013
Creator: Acree, William E. (William Eugene)
Partner: UNT College of Arts and Sciences

IUPAC-NIST Solubility Data Series. 98. Solubility of Polycyclic Aromatic Hydrocarbons in Pure and Organic Solvent Mixtures: Revised and Updated. Part 2. Ternary Solvent Mixtures

Description: Article on the solubility of polycyclic aromatic hydrocarbons in pure and organic solvent mixtures. This work updates volumes 54, 58, and 59 in the IUPAC Solubility Data Series and presents solubility data for polycyclic aromatic hydrocarbon solutes dissolved in ternary organic solvent mixtures.
Date: February 28, 2013
Creator: Acree, William E. (William Eugene)
Partner: UNT College of Arts and Sciences

Wavelength and pulselength dependence of laser conditioning and bulk damage in doubler-cut KH2PO4

Description: An experimental technique has been utilized to measure the variation of bulk damage scatter with damaging fluence in plates of KH{sub 2}PO{sub 4} (KDP) crystals. Bulk damage in unconditioned and laser-conditioned doubler-cut KDP crystals has been studied using 527 nm (2{omega}) light at pulselengths of 0.3-10 ns. It is found that there is less scatter due to damage at fixed fluence for longer pulselengths. In particular, there is {approx}4X increase in fluence for equivalent scatter for damage at 2{omega}, 10 ns as compared to 0.30 ns in unconditioned KDP. The results for the unconditioned and conditioned KDP show that for all the pulselengths the scatter due to the bulk damage is a strong function of the damaging fluence ({phi}{sup -5}). It is determined that the 2{omega} fluence pulselength-scaling for equivalent bulk damage scatter in unconditioned KDP varies as {tau}{sup 0.30{+-}0.11} and in 3{omega}, 3ns ramp-conditioned KDP varies as {tau}{sup 0.27{+-}0.14}. The effectiveness of 2{omega} and 3{omega} laser conditioning at pulselengths in the range of 0.30-23 ns for damage induced 2{omega}, 3 ns is analyzed in terms of scatter. For the protocols tested (i.e. peak conditioning irradiance, etc.), the 3{omega}, 300 ps conditioning to a peak fluence of 3 J/cm{sup 2} had the best performance under 2{omega}, 3 ns testing. The general trend in the performance of the conditioning protocols was shorter wavelength and shorter pulselength appear to produce better conditioning for testing at 2{omega}, 3 ns.
Date: October 28, 2005
Creator: Adams, J J; Bruere, J R; Bolourchi, M; Carr, C W; Feit, M D; Hackel, R P et al.
Partner: UNT Libraries Government Documents Department


Description: Savannah River National Laboratory (SRNL) performed pilot-scale hydraulic/chemical testing of spherical resorcinol formaldehyde (RF) ion exchange (IX) resin for the River Protection Project-Hanford Tank Waste Treatment & Immobilization Plant (WTP) Project. The RF resin hydraulic cycle testing was conducted in two pilot-scale IX columns, 1/4 and 1/2 scale. A total of twenty-three hydraulic/chemical cycles were successfully completed on the spherical RF resin. Sixteen of these cycles were completed in the 24-inch IX Column (1/2 scale column). Hydraulic testing showed that the permeability of the RF resin remained essentially constant, with no observed trend in the reduction of the permeability as the number of cycles increased. The permeability during the pilot-scale testing was 3 times better than the design requirements of the WTP full-scale IX system. The RF resin bed showed no tendency to form fissures or pack more densely as the number of cycles increased. Particle size measurements of the RF resin showed no indication of particle size change (for a given chemical) with cycles and essentially no fines formation. The permeability of the resin bed was uniform with respect to changes in bed depth. Upflow Regeneration and Simulant Introduction in the IX columns revealed another RF resin benefit; negligible radial pressures to the column walls from the swelling of resin beads. The hydraulic and chemical performance of the spherical RF resin during cycle testing was found to be superior to all other tested IX resins. The pilot-scale testing indicates that the RF resin is durable and should hold up to many hydraulic cycles in actual radioactive Cesium (Cs) separation.
Date: May 28, 2009
Creator: Adamson, D.
Partner: UNT Libraries Government Documents Department

Black Holes, q-Deformed 2d Yang-Mills, and Non-perturbative Topological Strings

Description: We count the number of bound states of BPS black holes on local Calabi-Yau three-folds involving a Riemann surface of genus g. We show that the corresponding gauge theory on the brane reduces to a q-deformed Yang-Mills theory on the Riemann surface. Following the recent connection between the black hole entropy and the topological string partition function, we find that for a large black hole charge N, up to corrections of O(e^-N), Z_BH is given as a sum of a square of chiral blocks, each of which corresponds to a specific D-brane amplitude. The leading chiral block, the vacuum block, corresponds to the closed topological string amplitudes. The sub-leading chiral blocks involve topological string amplitudes with D-brane insertions at 2g-2 points on the Riemann surface analogous to the Omega points in the large N 2d Yang-Mills theory. The finite N amplitude provides a non-perturbative definition of topological strings in these backgrounds. This also leads to a novel non-perturbative formulation of c=1 non-critical string at the self-dual radius.
Date: January 28, 2005
Creator: Aganagic, Mina; Ooguri, Hirosi; Saulina, Natalia & Vafa, Cumrun
Partner: UNT Libraries Government Documents Department

Multiphonon Resonance Raman Scattering in InGaN

Description: In In{sub x}Ga{sub 1-x}N epitaxial films with 0.37 < x < 1 and free electron concentrations in the 10{sup 18} cm{sup -3} range, strong resonant Raman scattering of A{sub 1}(LO) phonon is observed for laser excitation in Raman scattering when excited above the direct band gaps. Examination of films with direct band gaps between 0.7 and 1.9 eV using laser energies from 1.9 to 2.7 eV shows that the resonance is broad, extending to up to 2 eV above the direct gap. Multiphonon Raman scattering with up to 5 LO phonons is also observed for excitation close to resonance in alloy samples; this is the highest number of phonon overtones ever observed for multiphonon scattering in a III-V compound under ambient conditions. Coupling of the electron plasmon to the LO phonon to form a longitudinal plasmon coupled mode of the type which is observed in the Raman spectra of n-GaN, appears not to occur in In{sub x}Ga{sub 1-x}N for x > 0.37.
Date: June 28, 2005
Creator: Ager, J. W., III; Walukiewicz, W.; Shan, W.; Yu, K. M.; Li, S. X.; Haller, E. E. et al.
Partner: UNT Libraries Government Documents Department