Digital Commons Network^™

Comparison Of Zeus Data With Standard Model Predictions For E+P → E+X Scattering At High X And Q2, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

Using the ZEUS detector at HERA, we have studied the reaction e+p → e+X for Q2 > 5000 GeV2 with a 20.1 pb-1 data sample collected during the years 1994 to 1996. For Q2 below 15000 GeV2, the data are in good agreement with Standard Model expectations. For Q2 > 35000 GeV2, two events are observed while 0.145 ± 0.013 events are expected. A statistical analysis of a large ensemble of simulated Standard Model experiments indicates that with probability 6.0%, an excess at least as unlikely as that observed would occur above some Q2 cut. For x > 0.55 and y > 0.25, four …

Measurement Of Elastic J/Ψ Photoproduction St Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

The reaction γ p → J/ψ p has been studied in ep interactions using the ZEUS detector at HERA. The cross section for elastic J/ψ photoproduction has been measured as a function of the photon-proton centre of mass energy W in the range 40 < W < 140 GeV at a median photon virtuality Q2 of 5 × 10-5 GeV2. The photoproduction cross section, σγp→J/ψp, is observed to rise steeply with W. A fit to the data presented in this paper to determine the parameter δ in the form σγp→J/ψp α Wδ yields the value δ = 0.92±0.14±0.10. The differential cross section dσ/d|t| is presented over the range |t| < 1.0 GeV2 where t is the square of the four-momentum exchanged at the proton vertex. dσ/d|t| falls exponentially with a slope parameter of 4.6 ± 0.4-0.6+0.4 GeV-2. The measured decay angular distributions are consistent with s-channel helicity conservation. © Springer-Verlag 1997.

Study Of Photon Dissociation In Diffractive Photoproduction At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

Diffractive dissociation of quasi-real photons at a photon-proton centre of mass energy of W ≈ 200 GeV is studied with the ZEUS detector at HERA. The process under consideration is γp → XN, where X is the diffractively dissociated photon system of mass MX and N is either a proton or a nucleonic system with mass MN < 2 GeV. The cross section for this process in the interval 3 < MX < 24 GeV relative to the total photoproduction cross section was measured to be σDpartial/σtot = 6.2 ± 0.2(stat) ± 1.4(syst)%. After extrapolating this result to the mass interval of mφ2 < MX2 < 0.05W2 and correcting it for proton dissociation, the fraction of the total cross section attributed to single diffractive photon dissociation, γp → Xp, is found to be σSD/σtot = 13.3 ± 0.5(stat) ± 3.6(syst)%. The mass spectrum of the dissociated photon system in the interval 8 < MX < 24 GeV can be described by the triple pomeron (IP IP IP) diagram with an effective pomeron intercept of αIP(0) = 1.12 ± 0.04(stat) ± 0.08(syst). The cross section for photon dissociation in the range 3 < MX < 8 GeV is significantly higher than that expected from the triple pomeron amplitude describing the region 8 < MX < 24 GeV. Assuming that this discrepancy is due to a pomeron-pomeron-reggeon (IP IP IR) term, its contribution to the diffractive cross section in the interval 3 < MX < 24 GeV is estimated to be fIP IP IR = 26 ± 3(stat) ± 12(syst)%. © Springer-Verlag 1997.

Investigation Of The Optical Properties Of Ordered Semiconductor Materials, Jack E. Mccrae Jr.

Theses and Dissertations

Optical studies have been conducted upon CdGeAs₂ and ZnGeP₂, two of the most promising semiconductors being developed for mid-infrared non-linear optics applications. These experiments included photoluminescence (PL) studies of both compounds as well as photoreflectance (PR) measurements upon CdGeAs₂. In addition, Hall effect measurements were carried out upon CdGeAs₂, to aid in interpretation of the optical data. PL was measured as a function of laser power, sample temperature, and crystal orientation for CdGeAs₂. One broad weak peak near 0.38 eV, and another somewhat narrower and often far brighter peak near 0.57 …

Four-Wave Mixing And Optical Phase Conjugation In Vertical Cavity Surface Emitting Devices, Gregory J. Vansuch

Theses and Dissertations

Four-wave mixing (FWM), a nonlinear optical process, was investigated in resonant cavity light emitting diodes (RCLEDs) and vertical cavity surface emitting lasers (VCSELs) below lasing threshold. These semiconductor photonic devices consisted of an optical gain region of quantum wells sandwiched between two distributed Bragg reflector (DBR) mirrors. Pump and probe lasers were injected into the devices to generate FWM. The dependence of FWM on bias current, pump laser power, and spectral and spatial separation between pump and probe lasers was investigated experimentally. A computer model of FWM based on the wave and carrier density equations was developed and agreed well …

A System For Collecting Milligram Quantities Of Cloud Condensation Nuclei, Darryl J. Alofs, Donald E. Hagen, Steven D. Medley, Daniel R. White, John L. Schmitt, Allen L. Williams

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An Experimental System to Collect Cloud Condensation Nuclei (CCN) Onto Filters in Amounts Sufficient for Chemical Analysis is Described. This Experimental Apparatus is Designed to Process Ambient Air at a Rate of More Than 1 M3/min. Two Identical Systems Have Been Built. One is Installed in a Laboratory at Rolla, MO. the Other is Installed on an 11 M Long Trailer. the System Isolates Three Size Classes of CCN, Having Mass Median Diameters of 0.27, 0.12, and 0.075 Μm, Respectively, and Mass Collection Rates of 11.5, 1.28, and 0.13 Mg/day, Respectively. the above Sizes and Collection Rates Are Obtained from …

Academy Recommendations On The Proposed Yucca Mountain Waste Repository: Overview And Criticisms, Kristin S. Shrader-Frechette

RISK: Health, Safety & Environment (1990-2002)

Offers alternative criticism of the NAS report.

Three-Dimensional Direct Simulation Monte Carlo Method For Slider Air Bearings, Alejandro Garcia, W. Huang, D. B. Bogy

Faculty Publications

The direct simulation Monte Carlo (DSMC) method is used to solve the three-dimensional nano-scale gas film lubrication problem between a gas bearing slider and a rotating disk, and this solution is compared to the numerical solution of the compressible Reynolds equations with the slip flow correction based on the linearized Boltzmann equation as presented by Fukui and Kaneko [molecular gas film lubrication (MGL) method] [ASME J. Tribol. 110, 253 (1988)]. In the DSMC method, hundreds of thousands of simulated particles are used and their three velocity components and three spatial coordinates are calculated and recorded by using a hard-sphere collision …

Summing Up: Questions And Answers On The Comprehensive Test Ban Treaty, David W. Hafemeister

Physics

My experiences with the ratification of the Strategic Arms Reduction Treaty, the Threshold Test Ban Treaty, and the Conventional Armed Forces in Europe Treaty have led me to conclude that presenting technical issues early in the process greatly reduces their politicization during the ratification end game. This chapter summarizes the important issues that will be raised during the debate on ratification of the Comprehensive Test Ban Treaty. It uses a compact question and answer format to cover the following topics: I. Nuclear Proliferation, II. Nuclear Arms Control, III. Warhead Reliability and Yield for National Security, IV. Warhead Safety, V. Verification, …

A Child's Flashlight And Rc Circuit Concepts, Matthew J. Moelter, Rand S. Worland

Physics

No abstract provided.

Harmonic Oscillation In The Presence Of Multiple Damping Forces, Chris Pelto '97

Honors Projects

The relatively mundane damped harmonic oscillator is found to exhibit interesting motion once under the influence of both a velocity dependent and a Coulombic frictional damping force. Data for the decay of the amplitude as a function of time were collected on a specially prepared torsional oscillator. with a variable electromagnetic damping mechanism. An analytical solution of the appropriate equation of motion was obtained by the method of Laplace transforms. In both the limits of zero Coulombic friction and zero velocity damping, the solution reduces to the well-known answers to the problem. the solution, when plotted with the correct parameters, …

Droplet Concentration And Size Distribution In Haze And Fog, Josef Podzimek

Physics Faculty Research & Creative Works

Fog (haze) droplet concentrations and size distributions were measured at five sampling sites representing rural and urban regions and a highly polluted marine-urban environment. Droplet imprints in a thin gelatine layer were evaluated and compared to the measurement by light scattering instruments. This enabled conditions for the application of the logarithmic-normal size distribution and for the classification of typical fog droplet size distributions to be established. In particular, the parameters featuring the width and asymmetry of a size distribution were suggested and calculated. Advantages and drawbacks of the applied droplet sampling and evaluation technique are discussed in more detail. © …

The Effect Of Three-Dimensional Freestream Disturbances On The Supersonic Flow Past A Wedge, Peter W. Duck, D. Glenn Lasseigne, M. Y. Hussaini

Mathematics & Statistics Faculty Publications

The interaction between a shock wave (attached to a wedge) and small amplitude, three-dimensional disturbances of a uniform, supersonic, freestream flow are investigated. The paper extends the two-dimensional study of Duck et al. [P W. Duck, D. G. Lasseigne, and M. Y. Hussaini, ''On the interaction between the shock wave attached to a wedge and freestream disturbances,'' Theor. Comput. Fluid Dyn. 7, 119 (1995) (also ICASE Report No. 93-61)] through the use of vector potentials, which render the problem tractable by the same techniques as in the two-dimensional case, in particular by expansion of the solution by means of …

Observation Of Upper Tropospheric Sulfur Dioxide- And Acetone-Pollution: Potential Implications For Hydroxyl Radical And Aerosol Formation, F. Arnold, J. Schneider, K. Gollinger, H. Schlager, P. Schulte, Donald E. Hagen, Philip D. Whitefield, Peter F. J. Van Velthoven

Physics Faculty Research & Creative Works

Aircraft-based measurements of sulfur dioxide, acetone, carbon dioxide, and condensation nuclei (CN) were made over the north-eastern Atlantic at upper tropospheric altitudes, around 9000 m. On October 14, 1993, strong SO ₂- and acetone-pollution (both up to 3 ppbv) were observed, which were accompanied by a CO ₂-enhancement of up to 6 ppmv, and large CN-concentrations of up to about 1500 cm ^-3 (for radii ≥ 6 nm). CN, excess CO ₂, and to a lesser degree also acetone, were positively correlated with SO ₂. Air mass trajectory analyses indicate, that most of the air masses …

Spectroscopic And Kinetic Studies Of Bismuth Dimers, Robert Eugene Frankin

Theses and Dissertations

The spectroscopy of high rotational levels (J ≤ 211) in Bi₂ X(O_g⁺) and A(O_u⁺) was investigated for 2≤v"≤5 and 0≤v'≤4 by observing total fluorescence from laser excitation. Dunham coefficients were derived that fit all observed rotational lines to within 0.01 cm^-1. Franck-Condon factors were calculated and experimentally verified for transitions originating from the initially populated levels 0≤v'≤5. Vibrational energy transfer upon collision with rare gas collision partners was investigated for the low-lying vibrational levels of the A-state using spectrally resolved, continuous wave laser induced fluorescence. Vibrational transfer was adequately modeled by …

Inner-Shell Excitation Spectroscopy Of Closo-Carboranes, Adam P. Hitchcock, Stephen G. Urquhart, Alex T. Wen, A. L. David Kilcoyne, Tolek Tyliszczak, Eckart Rühl, Nobuhiro Kosugi, John D. Bozek, James T. Spencer, David N. Mcilroy, Peter A. Dowben

Peter Dowben Publications

Oscillator strength spectra in the region of B 1s and C 1s excitation of three isomeric carborane cage compounds [closo-1,2-orthocarborane, closo-1,7-metacarborane, closo-1,12-paracarborane (C₂B₁₀H₁₂)] have been derived from inner-shell electron energy loss spectra (ISEELS) recorded under electric dipole-scattering conditions. Total ion yield spectra recorded at high resolution with synchrotron radiation are also reported. The spectral features are assigned on the basis of comparisons with spectral predictions derived from the results of ab initio and semiempirical (extended Hückel) molecular orbital calculations. The isomeric and core level variations in the discrete core excitations …

Prediction Of Firing Pin Shape And 3d Matching Of Shells And Firing Pins Based On Firing Pin Impressions In Primers, Donald W. Dawson, Chris Hart, Bernard S. Gilbert Iii, Rafael A. Andrade, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A variable resolution video machine vision system has been built which will determine the 3-D shape of a firing pin from the dent it has made in the primer of a shell. The system can also compare primer dents in different shells and determine if a 3-D match exists. A real time optical 3-D shape recognition feature allows the operator to align the shells, determine if there is a match, and quantify the quality of the 3-D match. The system uses a laser interferometer to project variable spatial frequency structural illumination on the shells which are viewed by video cameras. …

Real Time 3-D Video Moire Inspection System With Enhanced Depth Resolution, Donald W.W. Dawson, Chris L. Hart, Bernard R. Gilbert, Gary L. Wallace, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A variable resolution video machine vision systems has been built which generates twice the number of depth contours for a given grating spacing as a conventional moiré system. This variable resolution system uses a Mach-Zender interferometer to project interference fringes onto a reference surface and onto a target surface. Video images of the two structurally illuminated surfaces are mixed in a video mixer with the resulting output being moiré contours which are the intersections of the two surfaces. If the reference surface is a flat plate, we get equal depth contours of the target surface, and if the reference surface …

Analysis Of Scanning Tunneling Optical Spectroscopy Applied To Narrow Gap Semiconductors, James D. Patterson, James G. Mantovani

Aerospace, Physics, and Space Science Faculty Publications

Homogeneous II-VI narrow gap semiconducting alloys are of interest because of their use in infrared detectors. These compound semiconductor materials are inherently difficult to grow in bulk due to gravity induced convective flows. A microgravity growth environment has therefore been considered. In order to evaluate the quality of crystals grown in space compared to those grown on the ground, it is necessary to characterize both. One important aspect of this characterization is the study of stoichiometry, x. A characterization scheme using scanning tunneling optical spectroscopy (STOS) involves determining the spectral response of the photoexcited tunneling current for a semiconductor. By …

Characterization Of Iron Oxides And Atmospheric Corrosion Of Steel, Sei Jin Oh

Physics Theses & Dissertations

The study of corrosion behavior was performed using three different analytical techniques, which provided information on the formation, development and layering of iron oxides on the corrosion products as a function of atmospheric conditions, exposure time and type of steel. In particular, the protective layer formed on weathering steel was investigated as a function of different amounts of alloying elements in the steel, atmospheric conditions and exposure times. Combined together, the results provided a better understanding of the atmospheric corrosion behavior of steel, and formed a part of database of the atmospheric corrosion characteristics.

Accurate characterization of the iron oxides …

Reflection High-Energy Electron-Diffraction Study Of Melting And Solidification Of Pb On Graphite, Z. H. Zhang, P. Kulatunga, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The melting and solidification of Pb thin films on pyrolytic graphite are investigated in situ by reflection high-energy electron diffraction. Thin films with thicknesses of 4-150 monolayers are investigated. The surface morphology of the thin films were studied by scanning electron microscopy. Superheating of the Pb thin films by 4±2 to 12±2 K is observed from diffraction intensity measurements. Upon cooling the substrate, the Pb on graphite is seen to supercool by ∼69±4 K.

Femtosecond Photoemission Study Of Ultrafast Electron Dynamics On Cu(100), J. Cao, Y. Gao, R. J. D. Miller, Hani E. Elsayed-Ali, D. A. Mantell

Electrical & Computer Engineering Faculty Publications

The energy dependence of the relaxation of photoexcited electrons in copper was measured using femtosecond time-resolved photoemission spectroscopy to within 0.3 eV above the Fermi level. By performing lifetime measurements under different surface conditions, several surface dynamical processes were investigated. In particular, an anomalous long lifetime feature, which cannot be explained with Fermi-liquid theory, was observed in the lifetime-energy curve. This feature was found originating from the photoexcitation of the strongly localized Cu 3d electrons. ©1997 American Physical Society

Microwave Plasma Chemical Vapor Deposited Diamond Tips For Scanning Tunneling Microscopy, Sacharia Albin, Jianli Zheng, John B. Cooper, Weihai Fu, Arnel C. Lavarias

Electrical & Computer Engineering Faculty Publications

Diamond microparticles were grown on etched tungsten wires using a microwave plasma-assisted chemical vapor deposition process. The apexes on cubo-octahedral particles bound by {100} and {111} facets were effectively used as tunneling tips for scanning tunneling microscopy. The atomically resolved surface image of highly oriented pyrolytic graphite was acquired. Tunneling characteristics revealed a higher electron emission from the diamond tips than that from the platinum–iridium tips. The same diamond tips were used to produce surface indentation and its image. © 1997 American Institute of Physics.

Turbulence Modeling Of The Toroidal Wall Heat Load Due To Shear Flows Over Cavities In The Neutral Gas Blanket Divertor Regime, George Vahala, Linda L. Vahala, Joseph Morrison

Electrical & Computer Engineering Faculty Publications

Heat loads to the target plate in reactor tokamaks are estimated to be orders of magnitude higher than those that can be withstood by known materials. In regimes of plasma detachment, there is strong evidence that plasma recombination occurs near the divertor plate, leading to a cold neutral gas blanket. Because of the strong coupling between the plasma and the neutrals within the divertor region, there is significant neutral flows along field lines up to Mach 1.2 and Reynolds numbers over 1000. The effects of three dimensional (3D) neutral turbulence within the gas blanket on heat deposition to the toroidal …

Modeling And Simulation Of Optical Characteristics Of Microelectromechanical Mirror Arrays, Peter C. Roberts

Theses and Dissertations

MEMS (Micro-Electro-Mechanical Systems) micromirror devices can be used to control the phase of a propagating light wavefront, and in particular to correct aberrations that may be present in the wavefront, due to either atmospheric turbulence or any other type of fixed or time and space varying aberrations. In order to shorten the design cycle of MEMS micromirror devices, computer software is developed to create, from MEMS micromirror device design data, a numerical model of the MEMS device. The model is then used to compute the far field diffraction pattern of a wavefront reflected from the device, and to predict the …

Comparison Of The Temperature-Dependent Electronic Structure Of The Perovskites La0.65Ca0.35Mno3 (A=Ca, Ba), D.N. Mcilroy, C. Waldfried, Jiandi Zhang, Jaewu Choi, F. Foong, Sy_Hwang Liou, Peter A. Dowben

Peter Dowben Publications

The electronic band structure and the local screening effects of the transition-metal perovskites La_0.65A_0.35MnO₃ (A=Ba and Ca ) have been examined across the coupled magnetic-metallic phase transition using the techniques of angle-resolved photoemission, resonance photoemission, and inverse photoemission. Temperature-dependent band shifts of the e_g and t_2g bands of La_0.65Ca_0.35MnO₃ have been observed. These changes in the observed electronic structure correlate with the phase transition, and are in qualitatively agreement with the predicted behavior associated with double exchange coupled with a dynamic Jahn-Teller distortion. Similar shifts were not observed …

Lower And Upper Bounds On Internal-Wave Frequencies In Stratified Rotating Fluids, Benoit Cushman-Roisin

Dartmouth Scholarship

According to classical theories, the frequencies of internal-gravity waves in stratified rotating fluids must lie between the Brunt-Väisälä frequency (a measure of the vertical density stratification) and the Coriolis frequency (equal to twice the rotation rate about the vertical axis). It is shown here that, in the case of the Earth's rotation where the pole-to-pole axis of rotation is almost everywhere not parallel to the local vertical, the range of realizable frequencies is broader. New formulas are derived for the lower and upper bounds of the frequencies.

Electrical Characterization Of Intrinsic And Induced Deep Level Defects In Hexagonal Sic, James D. Scofield

Theses and Dissertations

Deep level defects in hexagonal SiC were studied using digital deep level transient spectroscopy (DLTS) methods over the temperature range of 100 to 800 deg K. New centers were found in bulk and epitaxial 6H-SiC with ionization energies between 0.38 to 1.3 eV, and levels from 0.2 to 0.856 eV were identified in 4H-SiC epitaxy. Direct correlation between inequivalent lattice sites was identified for energetic pairs associated with both vanadium and ion implanted Mg impurities. Nonradioative carrier capture mechanisms were studied and deep level trapping was found to proceed via lattice relaxation multi-phonon emission, indicating efficient electronic lattice coupling in …

Theoretical Modeling Of Linear Absorption Coefficients In Si/Si1-Xgex Multiple Quantum Well Photodetectors, Kevin D. Greene

Theses and Dissertations

Si/Si_1-xGe_x MQW Infrared Photodetectors offer the promise of normal incidence photodetection tunable over the range of 3-12 micrometers wavelength range at temperatures above 40 K. This system is attractive because the Si_1-xGe_x offers greater compatibility with existing Si based signal processing circuitry. Band structures, momentum matrix elements and linear absorption coefficients are computed using a Luftinger-Kohn k/p analysis for Si/Si_1-xGe_x quantum wells grown in the 110 direction. The absorption coefficient as a function of energy and wavelength is calculated by two methods: a delta function fit to intersubband transitions, and a …

Laser-Induced Breakdown Spectroscopy On Solution Samples Using Surface Excitation, Leonard M. Berman

Theses and Dissertations

Laser-induced breakdown spectroscopy (LIBS) is a spectroscopic technique where output from a pulsed laser is focused onto a target in order to create an intense plasma. The optical emission is characteristic of the elements in the focal volume and can be used for elemental analysis. Research on the detection of nickel in solution in addition to solvent detection of CCl₄, CHCl₃, C2Cl₄, and C2HCl₃ has been performed. Breakdown was formed at the sample surface via a Q-switched Nd:YAG laser. Initially, operation of the laser was at 1064 nm/repetition rate of 5 Hz. Experiments …