Physical Sciences and Mathematics Commons^™

Soft And Hard Interactions In Pp̅ Collisions At √S =1800 And 630 Gev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a study of pp̅ collisions at √s =1800 and 630 GeV collected using a minimum bias trigger by the CDF experiment in which the data set is divided into two classes corresponding to “soft” and “hard” interactions. For each subsample, the analysis includes measurements of the multiplicity, transverse momentum (p_T) spectrum, and the average p_T and event-by-event p_T dispersion as a function of multiplicity. A comparison of results shows distinct differences in the behavior of the two samples as a function of the center of mass (c.m.) energy. We find evidence that the …

High-Mass Dijet Cross Sections In Photoproduction At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

Dijet differential cross sections for the reaction e+ p → e+ + jet + jet + X in the photoproduction regime have been measured with the ZEUS detector at HERA using an integrated luminosity of 42.7 pb-. The cross sections are given for photon-proton centre-of-mass energies in the range 134 < W < 277 GeV. The differential cross sections as a function of the dijet mass, MJJ, and of the dijet angular variables have been measured for 47 < MJJ < 160 GeV and compared to next-to-leading-order QCD calculations. The dijet events in the region 75 < MJJ < 100 GeV have been used to derive a 95% C.L. upper limit on the cross section for Z0 photoproduction of σ e+p→e+Z0X < 5.9 pb. Upper limits on the photoproduction of new heavy resonances decaying into two jets are also presented for masses in the range between 60 GeV and 155 GeV. © 2002 Elsevier Science B.V. All rights reserved.

Orientation-Controlled Nonepitaxial L10 Copt And Fept Films, H. Zeng, M.L. Yan, Nathan D. Powers, David J. Sellmyer

David Sellmyer Publications

We report results on highly oriented, face-centered tetragonal ordered CoPt and FePt thin films grown nonepitaxially by directly depositing films on thermally oxidized Si substrates and subsequent annealing. By controlling the thickness, composition, and annealing conditions, and/or depositing a proper underlayer, nearly perfect (001)-oriented CoPt and FePt films can be obtained. Magnetic measurements reveal large perpendicular anisotropy for such films.

Dissociative Electron Attachment To Molecules In The Gas Phase And In Rare Gas Solids, Paul Burrow, Kayvan Aflatooni

Paul Burrow Publications

Measurements of dissociative electron attachment (DEA) cross sections in chloroalkanes and chlorofluoromethanes have shown strong correlations between the peak DEA cross sections and the vertical attachment energies (VAEs) of these compounds. We explore the extent to which these gas phase data can be used to predict such cross sections for molecules embedded within or on the surface of a Kr solid. Effective VAEs are computed that include polarization of the solid by the anion and effects due to electron motion in the lattice. Comparisons are made with recent surface and bulk measurements and show good agreement for CF₃Cl …

Physica Junior!: The Newsletter Of Utep's Department Of Physics, Utep Department Of Physics

The Department of Physics

Electronic newsletter for high school students interested in Physics, Spring 2002.

Physica: The Newsletter Of Utep's Department Of Physics, Utep Department Of Physics

The Department of Physics

Electronic newsletter for the UTEP Department of Physics, Spring 2002.

Direct Observation Of Magnetic Domains In Phase Separated Nd0.7ca0.3mno3 Single Crystals, Xiaojuan Fan, Hideomi Koinuma, Tetsuya Hasegawa

Physics Faculty Research

The magnetic properties of single-crystalline Nd_0.7Ca_0.3MnO₃ were studied with both macroscopic and microscopic probes. The magnetization shows large irreversibility behavior between zero-field-cooled and field-cooled data at low field, suggesting a phase separation driven by competition between ferromagnetic and antiferromagnetic phases. The scanning superconducting quantum interference device microscope observations under zero field gave clear evidence that the compound includes ferromagnetic regions as the ground state below T_c. It was also found that two different phase-separated states appear, depending on temperature. At T∼125 K, weak but finite spontaneous magnetization develops, while the magnetization is abruptly enhanced …

Ulf Waves In The Solar Wind As Direct Drivers Of Magnetospheric Pulsations, L. Kepko, Harlan E. Spence, H. J. Singer

Physics & Astronomy

[1] Global magnetospheric ULF pulsations with frequencies in the Pc 5 range (f = 1.7–6.7 mHz) and below have been observed for decades in space and on the Earth. Recent work has shown that in some cases these pulsations appear at discrete frequencies. Global cavity and waveguide modes have been offered as possible sources of such waves. In these models the magnetosphere is presumed to resonate globally at frequencies determined solely by its internal properties such as size, shape, field topology, mass density distribution, etc. We show in this work that upstream solar wind number density and dynamic pressure …

A Short History Of Valence Bond Theory, Gordon A. Gallup

Gordon Gallup Publications

Shortly after quantum mechanics evolved Heitler and London [1] applied the then new ideas to the problem of molecule formation and chemical valence. Their treatment of the H₂ molecule was qualitatively very successful, and this led to numerous studies by various workers applying the same ideas to other substances. Many of these involved refinements of the original Heitler-London procedure, and within three or four years, a group of ideas and procedures had become reasonably well codified in what was called the valence bond (VB)* method for molecular structure.

A few calculations were carried out earlier, but by 1929 Dirac …

Dissipative Heating And Quasar Emission Lines, Mark Bottorff, Gary J. Ferland

Physics and Astronomy Faculty Publications

Recent observations reveal that the profiles of emission lines of active galactic nuclei are too smooth to be produced by discrete thermal (T~10⁴ K) clouds. The lines may also be too bright to be powered by the continuum unless a large covering factor or additional heating mechanisms are present. We have been investigating one possible explanation of these observations, namely, that the clouds are turbulent. This paper focuses on observational effects caused by dissipation of turbulent energy into cloud heating. We find that internal heating can explain these observations. Clouds energized by both the ionizing continuum and …

Cross Sections Spring 2002, Department Of Physics And Astronomy

Cross Sections

No abstract provided.

Structure And Magnetic Properties Of Ferromagnetic Nanowires In Self-Assembled Arrays, H. Zeng, Ralph Skomski, L. Menon, Yi Liu, Supriyo Bandyopadhyay, David J. Sellmyer

David Sellmyer Publications

Static and dynamic aspects of the magnetization reversal in nanowire arrays are investigated. The arrays have been produced by electrodeposition of ferromagnetic metals (Fe, Co, and Ni) into porous anodic alumina templates, with diameters as small as 5 nm. The crystal structures of the nanowires are bcc (Fe) and fcc (Ni) and a mixture of fcc and hcp (Co), with grain sizes of a few nanometers. Magnetic properties as a function of temperature are investigated. The temperature dependence of coercivity can be understood in terms of thermal activation over an energy barrier with a 3/2-power dependence on the field. Coercivity …

Pore Structure, Barrier Layer Topography And Matrix Alumina Structure Of Porous Anodic Alumina Film, Yucheng Sui, B.Z. Cui, L. Martinez, R. Perez, David J. Sellmyer

David Sellmyer Publications

Different anodic voltages and methods were adopted to produce porous anodic alumina films (PAAF) in an aqueous solution of oxalic acid. Carbon tube growth by chemical vapor deposition (CVD) in the films was used to copy the internal pore structure and was recorded by transmission electron microscopy (TEM) photos. Atomic force microscope (AFM) was employed to obtain the topography of the barrier layer of the corresponding films. When the anodic voltage was 40 V and the two-step method adopted, the barrier layer of the film had domains with highly ordered hexagonal cell distribution, and the corresponding pores were straight. When …

Electron-Impact Excitation From The (4p⁵5s) Metastable States Of Krypton, Arati K. Dasgupta, Klaus Bartschat, D. Vaid, Alexei N. Grum-Grzhimailo, Don H. Madison, Milan Blaha, John L. Giuliani

Physics Faculty Research & Creative Works

Theoretical results from multistate semirelativistic Breit-Pauli R-matrix calculations and two first-order distorted-wave calculations are presented for electron-impact excitation of krypton from the (4p⁵5s) J = 0,2 metastable states to the (4p⁵5s) and (4p⁵5p) manifolds. Except for a few cases, in which the method to account for relativistic effects becomes surprisingly critical, fair overall agreement between the predictions from the various theoretical models is achieved for intermediate and high energies. However, significant discrepancies remain with the few available experimental data.

Doubly Differential Electron-Emission Spectra In Single And Multiple Ionization Of Noble-Gas Atoms By Fast Highly-Charged-Ion Impact, Tom Kirchner, Laszlo Gulyas, Robert Moshammer, Michael Schulz, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

Low-energy electron emission spectra are studied in collisions of 3.6 MeV/amu Au⁵³⁺ ions with neon and argon atoms for well-defined degrees of target ionization. We calculate doubly differential cross sections as functions of the recoil-ion charge state in the continuum-distorted-wave with eikonal initial-state approximation using a binomial analysis of the total and differential ionization probabilities, and compare them with the present and with previously published experimental data. Very good agreement is found for the single-ionization spectra and for double ionization of neon, while some discrepancies are observed in the spectra for double and triple ionization of argon.

Local Versus Nonlocal Order-Parameter Field Theories For Quantum Phase Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta

Physics Faculty Research & Creative Works

General conditions are formulated that allow us to determine which quantum phase transitions in itinerant electron systems can be described by a local Landau-Ginzburg-Wilson (LGW) theory solely in terms of the order parameter. A crucial question is the degree to which the order parameter fluctuations couple to other soft modes. Three general classes of zero-wave-number order parameters, in the particle-hole spin-singlet and spin-triplet channels and in the particle-particle channel, respectively, are considered. It is shown that the particle-hole spin-singlet class does allow for a local LGW theory, while the other two classes do not. The implications of this result for …

Correlated Alternative Side Chain Conformations In The Rna-Recognition Motif Of Heterogeneous Nuclear Ribonucleoprotein A1, Jacqueline Vitali, Jianzhong Ding, Jianzhong Jiang, Ying Zhang, Adrian R. Krainer, Rui-Ming Xu

Physics Faculty Publications

The RNA-recognition motif (RRM) is a common and evolutionarily conserved RNA-binding module. Crystallographic and solution structural studies have shown that RRMs adopt a compact α/β structure, in which four antiparallel β-strands form the major RNA—binding surface. Conserved aromatic residues in the RRM are located on the surface of the β-sheet and are important for RNA binding. To further our understanding of the structural basis of RRM—nucleic acid interaction, we carried out a high resolution analysis of UP1, the N-terminal, two-RRM domain of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1), whose structure was previously solved at 1.75–1.9 Å …

Visual And Lidar Observations Ofnoctilucent Clouds Above Logan, Utah, At 41.7°N, Vincent B. Wickwar, Michael J. Taylor, Joshua P. Herron, B. A. Martineau

All Physics Faculty Publications

Noctilucent clouds (NLCs) were observed from a midlatitude site (Logan, Utah) on the evenings of 22 and 23 June 1999 mountain daylight time. On both nights the clouds were seen for approximately an hour by experienced observers, and they were photographed. The NLC was also observed on the second evening for approximately an hour in the zenith with the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory, which is operated by the Center for Atmospheric and Space Sciences on the campus of Utah State University. These observations enabled several of the properties of the cloud to be determined. They were within …

Design And Construction Of A Radio Frequency Plasma Device, Matthew Highland '02

Honors Projects

We have constructed a radio frequency plasma device to study a wide range of phenomena including, power coupling between the plasma and the antenna and wave propagation. Our system includes a high vacuum chamber with mechanical and diffusion pumps, a radio frequency source magnetic field coils and a matching network.

Development Of A Data Acquisition And Analysis System, Michael V. Mores '02

Honors Projects

Plasma is the fourth and least understood state of matter. A more complete understanding of this state of matter has numerous practical applications, including fusion energy, space travel, materials synthesis, and thin film deposition. As such, there is an obvious motivation to study this state. To do this, we have constructed a radio-frequency plasma device at Illinois Wesleyan University. I have developed a data acquisition using LabVIEW software that can digitize eight analog signals, saving the data to disk for later analysis. I have also written analysis software using LabVIEW to extract meaningful information from Langmuir Probe Trace.

Interface Relaxation In Electrophoretic Deposition Of Polymer Chains: Effects Of Segmental Dynamics, Molecular Weight, And Field, Frank W. Bentrem, Jun Xie, Ras B. Pandey

Faculty Publications

Using different segmental dynamics and relaxation, characteristics of the interface growth is examined in an electrophoretic deposition of polymer chains on a three (2+1)-dimensional discrete lattice with a Monte Carlo simulation. Incorporation of faster modes such as crankshaft and reptation movements along with the relatively slow kink-jump dynamics seems crucial in relaxing the interface width. As the continuously released polymer chains are driven (via segmental movements) and deposited, the interface width W grows with the number of time steps t, W∝t^β, (β ~0.4-0.8), which is followed by its saturation to a steady-state value W_{s …}

Temperature Dependence Of Dark Current In A Ccd, Ralf Widenhorn, Morley M. Blouke, Alexander Weber, Armin Rest, Erik Bodegom

Physics Faculty Publications and Presentations

We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor and the apparent activation energy as described by the Meyer-Neldel rule. However, a more detailed analysis shows that the activation energy for the dark current changes in the temperature range investigated. This transition can be explained by the larger relative importance at high temperatures of the diffusion dark current and at low temperatures by the depletion dark current. The diffusion dark current, …

A Compact Method For Optical Induction Of Proximal Probe Heating And Elongation, Andres H. La Rosa, Hans D. Hallen

Physics Faculty Publications and Presentations

A tapered, metal-coated, optical fiber probe will elongate when heated by light input through a fiber. The induced motion can be used for data storage or nanostructuring of a surface. The elongation produced by this alignment-free system is measured with force feedback in a near-field scanning optical microscope (NSOM). The input light intensity controls the elongation magnitude, which ranges from a few nanometers to more than 100 nm. A 0.5-mW input energy yields ~20 nm of probe elongation. The elongation quantified here can create artifacts in any experiment using pulsed laser light with a NSOM or an atomic force microscope.

Decomposition Of Carbon Dioxide In A Capacitively Coupled Radio Frequency Discharge, Thao Hoang Dinh

Physics Theses & Dissertations

Decomposition of CO₂ was studied in a capacitively coupled radio frequency discharge using Martian Simulant Gas mixture that contains 95% CO₂. The discharge was operated at a gas pressure of 3 to 6 Torr and a discharge power density of less than 2.0 W/cm³. The main mechanism of the CO₂ decomposition process is the electron impact dissociation and the rate of the process depends on the electron density, Ne, the concentration of CO₂, and the reduced electric field, E/N. A self-consistent model was established to describe the CO …

Spin Structure Functions Of The Deuteron, Junho Yun

Physics Theses & Dissertations

Inclusive double spin asymmetries have been measured in [special characters omitted] using the CLAS detector and a polarized [special characters omitted] target at. Jefferson Lab in 1998. The goal of these measurements is to study the spin structure of the deuteron and the neutron in the low Q² transition region between the real photon point, where the Gerasimov-Drell-Hearn (GDH) sum rule is expected to be satisfied, and the deep inelastic scattering limit. The analysis and the results for virtual photon asymmetries, the spin structure function [special characters omitted] and its first moment within a Q² range of 0.2 …

Improvements In Wavelength Modulation Spectroscopy Using Ratios Of Higher Harmonics, James Michael Barrington

Electrical & Computer Engineering Theses & Dissertations

Experiments in Wavelength Modulation Spectroscopy have been conducted at Old Dominion University since 1996. The method provides a highly sensitive, nonintrusive method of probing gases. Research has concentrated on effectively modeling the higher harmonic shapes that are measured experimentally. Accurately modeling these signals will result in the ability to reliably extract the information contained in transition line shapes.

In order to accurately depict the signals, the theory must be thoroughly understood. This thesis develops the theory of Wavelength Modulation Spectroscopy from two aspects: a direct Fourier series expansion of a time varying intensity profile and through communication theory. In addition, …

Dijet Photoproduction At Hera And The Structure Of The Photon, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

The dijet cross section in photoproduction has been measured with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb-1. The events were required to have a virtuality of the incoming photon, Q2, of less than 1 GeV2 and a photon-proton centre-of-mass energy in the range 134 < Wγp < 277 GeV. Each event contains at least two jets satisfying transverse-energy requirements of ETjet1 > 14 GeV and ETjet2 > 11 GeV and pseudorapidity requirements of -1 < ηjet1,2 < 2.4. The measurements are compared to next-to-leading-order QCD predictions. The data show particular sensitivity to the density of partons in the photon, allowing the validity of the current parameterisations to be tested.

Three-Dimensional Dye Distribution In Photo-Oriented Liquid-Crystal Alignment Layers, S. Bardon, D. Coleman, N. A. Clark, T. Kosa, H. Yuan, Peter Palffy-Muhoray

Peter Palffy-Muhoray

The three-dimensional optical anisotropy of photo-buffed dye-doped polymer films and the resulting orientation imparted to a liquid crystal in contact are probed using total internal reflection. Although the linearly polarized writing light generates a uniaxial distribution of dye molecules, the polymer films are biaxial, a result of symmetry breaking by the film surface.

Experimental Quantum Cloning Of Single Photons, Antia Lamas-Linares, Christoph Simon, John C. Howell, Dik Bouwmeester

Mathematics, Physics, and Computer Science Faculty Articles and Research

Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by stimulated emission. In this context, the fundamental quantum limit to the quality of the clones is imposed by the unavoidable presence of spontaneous emission. In our experiment, a single input photon stimulates the emission of additional photons from a source on the basis of parametric down-conversion. This leads to the production of quantum clones with near-optimal fidelity. We also demonstrate universality of the copying procedure by showing that the same …

University Of Nevada, Las Vegas Advanced Accelerator Applications University Participation Program: Quarterly Report Fourth Quarter (December 2001 To February 2002), Anthony Hechanova

Transmutation Research Program Reports (TRP)

This Quarterly Report is a primary deliverable from the University of Nevada, Las Vegas (UNLV) Advanced Accelerator Applications (AAA) University Participation Program (UPP) Director to the U.S. Department of Energy (DOE) as described in the UNLV AAA proposal and Statement of Work for the Fourth Quarter.

The UNLV AAA UPP Director implements the program’s administration using staff from the Harry Reid Center for Environmental Studies (HRC) to ensure that work conducted under the UNLV AAA UPP meets program objectives. The UNLV AAA program consists of three components: Program Support, Research Infrastructure Augmentation, and Student Research.