Physical Sciences and Mathematics Commons^™

Search For Large Extra Dimensions In The Monojet +ET Channel With The Dø Detector, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We present a search for large extra dimensions (ED) in pp̅ collisions at a center-of-mass energy of 1.8 TeV using data collected by the DØ detector at the Fermilab Tevatron in 1994–1996. Data corresponding to 78.8 ± 3.9 pb^-1 are examined for events with large missing transverse energy, one high-p_T jet, and no isolated muons. There is no excess observed beyond expectation from the standard model, and we place lower limits on the fundamental Planck scale of 1.0 and 0.6 TeV for 2 and 7 ED, respectively.

Search For The Supersymmetric Partner Of The Top Quark In Dilepton Events From Pp̅ Collisions At √S=1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have searched for pair production of the supersymmetric partner of the top quark (stop) in 107 pb^-1 of pp̅ collisions at √s=1.8 TeV collected by the Collider Detector at Fermilab (CDF). Each stop is assumed to decay into a lepton, bottom quark, and supersymmetric neutrino. Such a scenario would give rise to events with two leptons, two hadronic jets, and a substantial imbalance of transverse energy. No evidence of such a stop signal has been found. We exclude stop masses in the region (80≤ m t̅≤135 GeV/c²) in the mass plane of stop versus …

Focusing Of Spin Polarization In Semiconductors By Inhomogeneous Doping, Yuriy V. Pershin Dr, Vladimir Privman

Faculty Publications

We study the evolution and distribution of nonequilibrium electron spin polarization in n-type semiconductors within the two-component drift-diffusion model in an applied electric field. Propagation of spin-polarized electrons through a boundary between two semiconductor regions with different doping levels is considered.We assume that inhomogeneous spin polarization is created locally and driven through the boundary by the electric field.We show that an initially created narrow region of spin polarization can be further compressed and amplified near the boundary. Since the boundary involves variation of doping but no real interface between two semiconductor materials, no significant spin polarization loss is expected. …

The Shapes Of Dirichlet Defects, Mark Bowick, Antonio De Felice, Mark Trodden

Physics - All Scholarship

If the vacuum manifold of a field theory has the appropriate topological structure, the theory admits topological structures analogous to the D-branes of string theory, in which defects of one dimension terminate on other defects of higher dimension. The shapes of such defects are analyzed numerically, with special attention paid to the intersection regions. Walls (co-dimension 1 branes) terminating on other walls, global strings (co-dimension 2 branes) and local strings (including gauge fields) terminating on walls are all considered. Connections to supersymmetric field theories, string theory and condensed matter systems are pointed out.

Threshold Electrodisintegration Of 3he, R S. Hicks, A Hotta, S Churchwell, X Jiang, Gerald Alvin Peterson, J Shaw, B Asavapibhop, M C. Berisso, P E. Bosted, K Burchesky, R A. Miskimen, S E. Rock

Gerald Alvin Peterson

Cross sections were measured for the near-threshold electrodisintegration of 3He at momentum transfer values of q=2.4, 4.4, and 4.7fm-1. From these and prior measurements the transverse and longitudinal response functions RT and RL were deduced. Comparisons are made against previously published and new nonrelativistic A=3 calculations using the best available nucleon-nucleon NN potentials. In general, for q<2fm-1 these calculations accurately predict the threshold electrodisintegration of 3He. Agreement at increasing q demands consideration of two-body terms, but discrepancies still appear at the highest momentum transfers probed, perhaps due to the neglect of relativistic dynamics, or to the underestimation of high-momentum wave-function components.

Iteration Methods For Approximating The Lowest Order Energy Eigenstate Of A Given Symmetry For One- And Two-Dimensional Systems, Chad Everett Junkermeier

Theses and Dissertations

Using the idea that a quantum mechanical system drops to its ground state as its temperature goes to absolute zero several operators are devised to enable the approximation of the lowest order energy eigenstate of a given symmetry; as well as an approximation to the energy eigenvalue of the same order.

Radio Polarization Of The Young High-Magnetic-Field Pulsar Psr J1119-6127, Fronefield Crawford, Nathan C. Keim

Physics

We have investigated the radio polarization properties of PSR J1119-6127, a recently discovered young radio pulsar with a large magnetic field. Using pulsar-gated radio imaging data taken at a center frequency of 2496 MHz with the Australia Telescope Compact Array, we have determined a rotation measure for the pulsar of +842 +/- 23 rad m^-2. These data, combined with archival polarimetry data taken at a center frequency of 1366 MHz with the Parkes telescope, were used to determine the polarization characteristics of PSR J1119-6127 at both frequencies. The pulsar has a fractional linear polarization of ~75% and ~55% at 1366 …

Inelastic Neutron Scattering Signal From Deconfined Spinons In A Fractionalized Antiferromagnet, Courtney Lannert, Matthew P.A. Fisher

Physics: Faculty Publications

We calculate the contribution of deconfined spinons to inelastic neutron scattering (INS) in the fractionalized antiferromagnet (AF*), introduced elsewhere. We find that the presence of free spin-1/2 charge-less excitations leads to a continuum INS signal above the Néel gap. This signal is found above and in addition to the usual spin-1 magnon signal, which to lowest order is the same as in the more conventional confined antiferromagnet. We calculate the relative weights of these two signals and find that the spinons contribute to the longitudinal response, where the magnon signal is absent to lowest order. Possible higher-order effects of interactions …

Application Of A Photopolymer Material In Speckle Pattern Shearing Interferometry, Emilia Mihaylova, Izabela Naydenova, Suzanne Martin, Vincent Toal

Conference Papers

A new application of a photopolymer diffractive optical element in electronic speckle pattern shearing interferometer (ESPSI) is presented. In the first stage a holographic grating is recorded using an acrylamide based photopolymer material. Since the polymerisation process occurs during recording, the holograms are produced without any development or processing. In the second stage the holographic grating is used to produce the two sheared images in an ESPSI configuration. A ground glass screen following the grating serves the purpose of eliminating unwanted diffraction orders. The distance between the grating and the ground glass can be used to control the amount of …

Nanoscale Polarization Manipulation And Conductance Switching In Ultrathin Films Of A Ferroelectric Copolymer, Hongwei Qu, Wei Yao, T. Garcia, Jiandi Zhang, A.V. Sorokin, Stephen Ducharme, Peter A. Dowben, V.M. Fridkin

Peter Dowben Publications

We report the direct observation of induced molecular reorientation on a ferroelectric copolymer with a scanning tunneling microscope (STM). Ultrathin copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%) revealed a quasihexagonal close-packing structure with long-range polymer chain ordering. By flipping the polarity of the STM tip bias voltage, a reversal of local polarization was observed through an apparent lattice shift and was accompanied by an asymmetric ‘‘diode-like’’ character in tunneling current I(V). These results clearly demonstrated conductance switching behavior on nanoscale with local polarization reversal. © 2003 American Institute of Physics.

Phase Ii: Design And Analysis Of A Process For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Yitung Chen, Randy Clarksean, Darrell Pepper

Fuels Campaign (TRP)

This research report develops a model to analyze the transport of americium from the melt to the vapor phase above the crucible. The model considers mass transport in the melt, vaporization at the surface, and transport through the vapor phase. The greatest problem with the model is the uncertainty of the thermodynamic properties of the proposed ternary alloy. The details of the model and the specific quantities needed for the physical properties will be discussed.

Theoretical Study On The Optical Properties Of Polyvinylidene Fluoride Crystal, Chun-Gang Duan, Wai-Ning Mei, Wei-Guo Yin, Jianjun Liu, J. R. Hardy, Mengjun Bai, Stephen Ducharme

Stephen Ducharme Publications

We report our first-principles studies on the linear and non-linear optical properties of ferroelectric polyvinylidene fluoride crystal. Calculated values of the refractive indices agree well with experiments. As regards the second-harmonic-generation coefficients, theoretical values are larger than experimental ones. Possible reasons for the discrepancy are discussed.

The Flaring H2o Megamaser And Compact Radio Source In Markarian 348, A. B. Peck, C. Henkel, J. S. Ulvestad, A. Brunthaler, H. Falcke, Moshe Elitzur, K. M. Menten, J. F. Gallimore

Physics and Astronomy Faculty Publications

We report on single-dish monitoring and extremely high angular resolution observations of the flaring H₂O megamaser in the Seyfert 2 galaxy Mrk 348. The H₂O line is redshifted by ~130 km s^-1 with respect to the systemic velocity, is very broad, with an FWHM of 130 km s^-1, and has no detectable high-velocity components within 1500 km s^-1 on either side of the strong line. Monitoring observations made with the Effelsberg 100 m telescope show that the maser varies significantly on timescales as short as 1 day and that the integrated line …

Radiative Decays Involving A0(980) And F0(980) In The Vector Meson Dominance Model, Joseph Schechter, Deirdre Black, Masayasu Harada

Physics - All Scholarship

We summarize some features of the vector meson dominance model which was recently proposed for studying radiative decays involving the scalar mesons. Using the experimental values of \Gamma(a_0 \to \gamma\gamma), \Gamma(f_0 \to \gamma\gamma) and \Gamma(\phi \to a_0 \gamma) as inputs, we show that the model predicts a large hierarchy between \Gamma(a_0 \to \omega \gamma) and \Gamma(a_0 \to \rho \gamma) as well as between \Gamma(f_0 \to \omega \gamma) and \Gamma(f_0 \to \rho \gamma).

Laboratory Simulation Of Charge Exchange - Produced X-Ray Emission From Comets, P. Beiersdorfer, K. R. Boyce, G. V. Brown, H. Chen, S. M. Kahn, R. L. Kelley, M. May, Ronald E. Olson, F. S. Porter, C. K. Stahle, W. A. Tillotson

Physics Faculty Research & Creative Works

In laboratory experiments using the engineering spare microcalorimeter detector from the ASTRO-E satellite mission, we recorded the x-ray emission of highly charged ions of carbon, nitrogen, and oxygen, which simulates charge exchange reactions between heavy ions in the solar wind and neutral gases in cometary comae. the spectra are complex and do not readily match predictions. We developed a charge exchange emission model that successfully reproduces the soft x-ray spectrum of comet Linear C/1999 S4, observed with the Chandra X-ray Observatory.

Search For Associated Production Of Υand Vector Boson In Pp̅ Collisions At √S =1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a search for associated production of the Υ (1S) and a vector boson in 83 pb^-1 of pp̅ collisions at √s =1.8 TeV collected by the CDF experiment in 1994–1995. We find no evidence of the searched signal in the data, and set upper limits to the production cross sections.

Observations Of Discrete, Global Magnetospheric Oscillations Directly Driven By Solar Wind Density Variations, L. Kepko, Harlan E. Spence

Physics & Astronomy

No abstract provided.

Предсказание Термодинамики И Упорядочения В Металлических Сплавах Из Первых Принципов, Николай Заркевич

Nikolai A. Zarkevich

Кластерные разложения по взаимодействиям все чаще используются для много- масштабного моделирования, сочетающего расчёты электронной структуры из первых принципов и методы Монте-Карло для предсказания термодинамических свойств сплавов. Кластерное разложение – это разложение по базису геометрических объектов (кластеров) на решётке и эффективных межатомных взаимодействий. Кластерное разложение может быть математически точным и бесконечным, но практично только в усечённом конечном базисе. Однако до сих пор процедура усечения базиса не была строго определена и не гарантировала надёжный результат. Мы предлагаем метод оптимального усечения базиса геометрических кластеров, который ведёт к надёжным предсказаниям термодинамики. Далее для примера мы проводим количественный расчёт термодинамических свойств ГЦК сплава Ni3V и …

Mobility Of Taxol In Microtubule Bundles, Jennifer Ross, D. Kuchnir Fygenson

Jennifer Ross

Mobility of taxol inside microtubules was investigated using fluorescence recovery after photobleaching on flowaligned bundles. Bundles were made of microtubules with either GMPCPP or GTP at the exchangeable site on the tubulin dimer. Recovery times were sensitive to bundle thickness and packing, indicating that taxol molecules are able to move laterally through the bundle. The density of open binding sites along a microtubule was varied by controlling the concentration of taxol in solution for GMPCPP samples. With [63% sites occupied, recovery times were independent of taxol concentration and, therefore, inversely proportional to the microscopic dissociation rate, koff. It was found …

Thickness Dependence Of Magnetic Blocking In Granular Thin Films With Interacting Magnetic Particles, Jian Qing Wang, Zhi Dong Zhao, Scott L. Whittenburg

Chemistry and Biochemistry Faculty Publications

Interparticle interaction among single domain nanosize magnetic particles embedded in nonmagnetic matrix was studied. Attention was paid to concentrated Cu–Co granular thin films with a fixed magnetic volume fraction (20%). By analyzing theoretical models and comparing with experimental results, a dimensional constraint on the magnetic properties was found. As the film thickness reduces toward the thin limit the interparticle interaction plays important roles in modifying the magnetic behavior. The dipolar interaction energy was calculated among magnetic particles including far-neighbor interaction for films with different thickness values. When magnetization variation is included in the calculation, the resulting calculated interaction energy versus …

Suprathermal Electron Isotropy In High-Beta Solar Wind And Its Role In Heat Flux Dropouts, N. U. Crooker, D. E. Larson, S. W. Kahler, S. M. Lamassa, Harlan E. Spence

Physics & Astronomy

[1] Time variations in plasma beta and a parameter which measures isotropy in suprathermal electron pitch angle distributions show a remarkably close correspondence throughout the solar wind. The finding implies that high-beta plasma, with its multiple magnetic holes and sharp field and plasma gradients, is conducive to electron pitch-angle scattering, which reduces heat flux from the Sun without field-line disconnection. Thus the finding impacts our understanding of signatures we use to determine magnetic topology in the heliosphere.

Projectile-Charge Sign Dependence Of Four-Particle Dynamics In Helium Double Ionization, Daniel Fischer, Robert Moshammer, Alexander Dorn, Jose R. Crespo Lopez-Urrutia, Bernold Feuerstein, C. Hohr, Claus Dieter Schroter, Siegbert Hagmann, Holger Kollmus, Rido Mann, Bhas Bapat, Joachim Hermann Ullrich, Holger Kollmus

Physics Faculty Research & Creative Works

Double ionization of helium by 6 MeV proton impact has been explored in a kinematically complete experiment using a “reaction microscope.” For the first time, fully differential cross sections for positively charged projectiles have been obtained and compared with data from 2 keV electron impact. The significant differences observed in the angular distribution of the ejected electrons are attributed to the charge sign of the projectile, resulting in different dynamics of the four-particle Coulomb system, which is not considered in the first Born approximation.

Optical Solitons In A Three-State Medium, Talal Ghannam

Masters Theses

When a beam of light propagates within a typical medium, absorption is a common phenomenon. This happens when the frequency of the light is close to a resonant frequency of the atoms composing the medium. But in the past few decades, it has been shown that in certain circumstances, carefully chosen pulse shapes are able to propagate without significant absorption even when the frequency of the light is close to an atomic resonant frequency. It was called Self Induced Transparency (SIT).

This phenomenon was intensively studied in the two-state systems. On the other hand, the three-state systems seems not to …

Effect Of H-2 On The Martian Ionosphere: Implications For Atmospheric Evolution, Jane L. Fox

Physics Faculty Publications

Because H₂ reacts efficiently with O⁺, CO₂ ⁺, CO⁺, and N₂ ⁺, the molecular hydrogen abundance assumed in models of the Martian ionosphere greatly affects the high altitude density profiles of these ions. We have found that models of the low solar activity Martian ionosphere exhibit much smaller O⁺ densities than the measured values if the adopted H₂ abundance is of the order of 40 ppm, the value proposed in a 1998 model of the Martian atmosphere. For a model based on the recently measured H₂ abundance of …

A Combined Heating Cooling Stage For Cluster Thermalization In The Gas Phase, D. N. Ievlev, A. Küster, Axel Enders, N. Malinowski, H. Schaber, Klaus Kern

Axel Enders Publications

We report on the design and performance of a combined heating/cooling stage for the thermalization of clusters in a gas phase time-of-flight mass spectrometer. With this setup the cluster temperature can sensitively be adjusted within the range from 100 up to 800 K and higher. The unique combination of a heating stage with a subsequent cooling stage allows us to perform thermodynamic investigations on clusters at very high temperatures without quality losses in the spectra due to delayed fragmentation in the drift tube of the mass spectrometer. The performance of the setup is demonstrated by the example of (C_{60 …}

Black Hole Attractor Varieties And Complex Multiplication, Monika Lynker, Vipul Periwal, Rolf Schimmrigk

Faculty Articles

Black holes in string theory compactified on Calabi-Yau varieties a priori might be expected to have moduli dependent features. For example the entropy of the black hole might be expected to depend on the complex structure of the manifold. This would be inconsistent with known properties of black holes. Supersymmetric black holes appear to evade this inconsistency by having moduli fields that flow to fixed points in the moduli space that depend only on the charges of the black hole. Moore observed in the case of compactifications with elliptic curve factors that these fixed points are arithmetic, corresponding to curves …

Use Of Optical Tweezers For Colloid Science, Andrew Resnick

Physics Faculty Publications

A space-borne optical tweezer apparatus for use with colloidal crystallization experiments has been characterized. The trapping force has been measured as a function of index mismatch between colloidal microspheres and the surrounding fluid and as a function of particle size. This work also presents a method to determine the refractive index of a colloidal microsphere, which is then used to calculate the applied trapping force for the case of an arbitrary background fluid. This is useful for work with dense colloidal suspensions when the usual (e.g., Stokes flow) trap force measurement methods do not apply, as well as microrheological studies …

Afci Quarterly Input – Unlv April Through June, 2003, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

Microspectrophotometry Of Respiratory Pigments, Karen Yvonne Kavanagh

Doctoral

This research thesis describes the design, construction and optical testing of three fibre-optic microspectrophotometer systems to monitor the reduction of mitochondrial respiratory pigments. The optical and biochemical characteristics of mitochondrial respiration are discussed and the current optical techniques employed in the biochemical analysis of respiratory enzymes are presented. The primary focus of this study is the system parameters surrounding the spectrophotometric determination of mitochondrial respiratory activity. Three separate fibre-optic set-ups are described, which use visible spectrophotometry to measure the reduction of mitochondrial electron carriers from a range of biological sources. Each system is based around the Ocean Optics S1000/S2000 series …

Localized Ferromagnetic Resonance In Inhomogeneous Thin Films, R. D. Mcmichael, D. J. Twisselmann, Andrew Kunz

Physics Faculty Research and Publications

The effect of sample inhomogeneity on the ferromagnetic resonance linewidth is determined by diagonalization of a spin wave Hamiltonian for ferromagnetic thin films with inhomogeneities spanning a wide range of characteristic length scales. A model inhomogeneity is used that consist of size D grains and an anisotropy field H_p that varies randomly from grain to grain in a film with thickness d and magnetization M_s. The resulting linewidth agrees well with the two-magnon model for small inhomogeneity, H_pD « πM_sd. For large inhomogeneity, H_pD » πM_sd the precession …