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2003

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Articles 1 - 30 of 566

Full-Text Articles in Physics

Pion-Kaon Correlations In Central Au+Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez Dec 2003

Pion-Kaon Correlations In Central Au+Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez

Physics

Pion-kaon correlation functions are constructed from central Au+Au STAR data taken at √sNN=130  GeV by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The results suggest that pions and kaons are not emitted at the same average space-time point. Space-momentum correlations, i.e., transverse flow, lead to a space-time emission asymmetry of pions and kaons that is consistent with the data. This result provides new independent evidence that the system created at RHIC undergoes a collective transverse expansion.


Anomaly In Conformal Quantum Mechanics: From Molecular Physics To Black Holes, Horacio E. Camblong Dec 2003

Anomaly In Conformal Quantum Mechanics: From Molecular Physics To Black Holes, Horacio E. Camblong

Physics and Astronomy

A number of physical systems exhibit a particular form of asymptotic conformal invariance: within a particular domain of distances, they are characterized by a long-range conformal interaction (inverse square potential), the apparent absence of dimensional scales, and an SO(2,1) symmetry algebra. Examples from molecular physics to black holes are provided and discussed within a unified treatment. When such systems are physically realized in the appropriate strong-coupling regime, the occurrence of quantum symmetry breaking is possible. This anomaly is revealed by the failure of the symmetry generators to close the algebra in a manner shown to be independent of ...


Diffusion And Drift In Terahertz Emission At Gaas Surfaces, James Heyman, N Coates, A Reinhardt, G Strasser Dec 2003

Diffusion And Drift In Terahertz Emission At Gaas Surfaces, James Heyman, N Coates, A Reinhardt, G Strasser

James Heyman

No abstract provided.


Projectile-Shape Dependence Of Impact Craters In Loose Granular Media, K. A. Newhall Dec 2003

Projectile-Shape Dependence Of Impact Craters In Loose Granular Media, K. A. Newhall

Department of Physics Papers

We report on the penetration of cylindrical projectiles dropped from rest into a dry, noncohesive granular medium. The cylinder length, diameter, density, and tip shape are all explicitly varied. For deep penetrations, as compared to the cylinder diameter, the data collapse onto a single scaling law that varies as the 1/3 power of the total drop distance, the 1/2 power of cylinder length, and the 1/6 power of cylinder diameter. For shallow penetrations, the projectile shape plays a crucial role with sharper objects penetrating deeper.


Three-Pion Hanbury Brown–Twiss Correlations In Relativistic Heavy-Ion Collisions From The Star Experiment, Star Collaboration, T.D. Gutierrez Dec 2003

Three-Pion Hanbury Brown–Twiss Correlations In Relativistic Heavy-Ion Collisions From The Star Experiment, Star Collaboration, T.D. Gutierrez

Physics

Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory, Au+Au collisions at √sNN=130   GeV, have been analyzed by the STAR Collaboration using three-pion correlations with charged pions to study whether pions are emitted independently at freeze-out. We have made a high-statistics measurement of the three-pion correlation function and calculated the normalized three-particle correlator to obtain a quantitative measurement of the degree of chaoticity of the pion source. It is found that the degree of chaoticity seems to increase with increasing particle multiplicity.


Resonant Emergence Of Global And Local Spatiotemporal Order In A Nonlinear Field Model, Marcelo Gleiser, Rafael C. Howell Dec 2003

Resonant Emergence Of Global And Local Spatiotemporal Order In A Nonlinear Field Model, Marcelo Gleiser, Rafael C. Howell

Open Dartmouth: Published works by Dartmouth faculty

We investigate the nonequilibrium evolution of a scalar field in (2+1) dimensions. The field is set in a double-well potential in contact (open) or not (closed) with a heat bath. For closed systems, we observe the synchronized emergence of coherent spatiotemporal configurations, identified with oscillons. This initial global ordering degenerates into localized order until all oscillons disappear. We show that the synchronization is driven by resonant parametric oscillations of the field’s zero mode and that local ordering is only possible outside equipartition. None of these orderings occur for open systems.


Fundamental And Magnetic-Hardening Studies Of Rare-Earth And Nanocomposite Magnets, David J. Sellmyer, George C. Hadjipanayis Dec 2003

Fundamental And Magnetic-Hardening Studies Of Rare-Earth And Nanocomposite Magnets, David J. Sellmyer, George C. Hadjipanayis

David Sellmyer Publications

In this project we study new nanocrystalline and nanocomposite structures that have high potential for permanent-magnet development. These materials, which can be synthesized to have either very high or intermediate coercivities, have many applications in electric power, transportation, and information-storage industries. There is great interest in further development of understanding and application of these materials. Following are brief discussions of recent research highlights for the present grant.


Prediction Of Dopant Ionization Energies In Silicon: The Importance Of Strain, A. Rockett, Duane D. Johnson, S. V. Khare, B. R. Tuttle Dec 2003

Prediction Of Dopant Ionization Energies In Silicon: The Importance Of Strain, A. Rockett, Duane D. Johnson, S. V. Khare, B. R. Tuttle

Duane D. Johnson

Based on a hydrogenic state and strain changes upon defect charging, we propose a simple, parameter-free model that agrees well with the observed group III and V monovalent-impurity ionization energies in Si, revealing the importance of such strain effects. Changes in lattice strain upon defect charging are obtained via superposition and elasticity theory using atomic relaxations from density functional theory.


Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher Dec 2003

Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher

Jeffrey Dyck

We have measured electrical and magnetic properties of single crystals of Sb2_xMnxTe3 with x =0 – 0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2– VI3 diluted magnetic semiconductors, at least ...


Strong Field Detachment Of A Negative Ion With Non-Zero Angular Momentum: Application To F-, M. V. Frolov, N. L. Manakov, E. A. Pronin, Anthony F. Starace Dec 2003

Strong Field Detachment Of A Negative Ion With Non-Zero Angular Momentum: Application To F-, M. V. Frolov, N. L. Manakov, E. A. Pronin, Anthony F. Starace

Anthony F. Starace Publications

We apply our recently developed, model-independent quantum approach for intense laser detachment of a weakly bound electron to interpret a recent experiment on above-threshold detachment (ATD) of the F- ion. We find that the measured electron energies correspond to the “Keldysh part” of the ATD spectrum, just below the onset of our predicted rescattering plateau. Overall, our predicted ATD spectrum (using a scaled peak intensity and focal averaging) is in excellent agreement with the experimental data, except for certain structures observed for electron energies above 12.6 eV that we attribute to known two-electron resonances of F-. A number of ...


Measurement Of Prompt Charm Meson Production Cross Sections In Pp̅ Collisions At √S=1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 2003

Measurement Of Prompt Charm Meson Production Cross Sections In Pp̅ Collisions At √S=1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on measurements of differential cross sections d /dpT for prompt charm meson production in pp̅ collisions at √s=1.96 TeV using 5.8±0.3 pb-1 of data from the CDF II detector at the Fermilab Tevatron. The data are collected with a new trigger that is sensitive to the long lifetime of hadrons containing heavy flavor. The charm meson cross sections are measured in the central rapidity region |y|≤1 in four fully reconstructed decay modes: D0K- π+, D*+→D0 π+, D+K- π+ π+, Ds+→ Φπ+, and their charge conjugates ...


Linear Perturbations In Brane Gas Cosmology, Scott Watson, Robert H. Brandenberger Dec 2003

Linear Perturbations In Brane Gas Cosmology, Scott Watson, Robert H. Brandenberger

Physics

We consider the effect of string inhomogeneities on the time dependent background of Brane Gas Cosmology. We derive the equations governing the linear perturbations of the dilaton-gravity background in the presence of string matter sources. We focus on long wavelength fluctuations and find that there are no instabilities. Thus, the predictions of Brane Gas Cosmology are robust against the introduction of linear perturbations. In particular, we find that the stabilization of the extra dimensions (moduli) remains valid in the presence of dilaton and string perturbations.


United States Patent: Application Of High Spin Polarization Materials In Two Terminal Non-Volatile Bistable Memory Devices, Bernard Doudin, Andrei Sokolov, Cheol-Soo Yang, Lu Yuan, Sy-Hwang Liou Dec 2003

United States Patent: Application Of High Spin Polarization Materials In Two Terminal Non-Volatile Bistable Memory Devices, Bernard Doudin, Andrei Sokolov, Cheol-Soo Yang, Lu Yuan, Sy-Hwang Liou

Si-Hwang Liou Publications

Disclosed are two terminal bistable memory cells having least two high-spin polarization magnetic material junctions which are separated from one another by electron trap site defect containing insulator. The two terminal bistable memory cells demonstrate stable, low current readable, hysteretic resistance states which are set by the flow of a relatively high, (eg. a milliamp or less), plus or minus polarity D.C. current therethrough, which resistance is monitored by lower magnitude A.C. or D.C. current flow therethrough. Preferred cells have at least one Cr02/Cr203/ CrO2 sequence but typically have multiple Cr0 ...


Physics Department News, December 2003, College Of Arts And Sciences Dec 2003

Physics Department News, December 2003, College Of Arts And Sciences

Physics Newsletter

Contents from Volume 2, Issue 2:

  • A Note from the Editor
  • From the Chair
  • What’s New at the University
  • Faculty Highlights
  • Staff Highlights
  • Accelerator Upgrade 5
  • PhysTEC
  • Distinguished Alumni Award
  • Alumni News
  • Recent Guest
  • Goldwater Scholar
  • New Grants
  • Student Awards
  • Recent Graduates
  • Department Roster
  • Photo Gallery
  • Feedback/Update Reply Form


Isotropic Loop Quantum Cosmology With Matter. Ii. The Lorentzian Constraint, F. Hinterleitner, Seth Major Dec 2003

Isotropic Loop Quantum Cosmology With Matter. Ii. The Lorentzian Constraint, F. Hinterleitner, Seth Major

Articles

The Lorentzian Hamiltonian constraint is solved for isotropic loop quantum cosmology coupled to a massless scalar field. As in the Euclidean case, the discreteness of quantum geometry removes the classical singularity from the quantum Friedmann models. In spite of the absence of the classical singularity, a modified DeWitt initial condition is incompatible with a late-time smooth behavior. Further, the smooth behavior is recovered only for positive or negatives times but not both. An important feature, which is shared with the Euclidean case, is a minimal initial energy of the order of the Planck energy required for the system to evolve ...


“Don’T Tell Me, I’Ll Find Out”: Robert Karplus—A Science Education Pioneer, Robert Fuller Dec 2003

“Don’T Tell Me, I’Ll Find Out”: Robert Karplus—A Science Education Pioneer, Robert Fuller

Robert G. Fuller Publications and Presentations

Robert Karplus (1927–90), who began his career as a brilliant theoretical physicist, switched to science education in the early 1960s. He made many substantial contributions to this field in addition to developing a complete K–6 hands-on science curriculum. Karplus provided his curriculum with a sound epistemological foundation, based on the work of Piaget. He developed an effective classroom teaching strategy, the learning cycle. He and his team used a scientific approach to curriculum development. They focused on teacher development. Karplus was committed to science for ALL students. Through science activities he sought to share the joy of discovery ...


A High Shear-Rate Optical Rheometer For Complex Fluids, Khaled S. Mriziq Dec 2003

A High Shear-Rate Optical Rheometer For Complex Fluids, Khaled S. Mriziq

Doctoral Dissertations

A parallel-plate optical rheometer in a magnetic-disc drive configuration has been designed and constructed of optically transparent materials and operating with a very small gap to obtain rheological and structural measurements at very high shear rates.

The friction force at the disk-slider interface has been measured as a function of sliding speed while the film thickness was monitored in situ using a capacitance technique. The shear rate is calculated from the film thickness and the sliding speed. A thin film can be applied on the disk, which allows very high-shear-rate measurements at low sliding speeds with negligible viscous heating.

Both ...


Production In Au-Au Collisions, Robert Jason Newby Dec 2003

Production In Au-Au Collisions, Robert Jason Newby

Doctoral Dissertations

This thesis presents the first J/ Ψ production analysis of Au+Au reactions at forward rapidity at p √sNN = 200 GeV. In the second year of RHIC running, design energy was achieved in the collisions of both Au+Au ions and proton+proton reactions. The production of the J/Ψ is measured by the PHENIX experiment in Au+Au collisions as well as in proton-proton collisions. The scientific goal is to investigate the nature of hot, dense nuclear matter capitalizing on the unique properties of the J/ Ψ as a probe of this matter. Recent experimental results by the NA50 ...


Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraft Charging, A Robb Frederickson, Jr Dennison Dec 2003

Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraft Charging, A Robb Frederickson, Jr Dennison

Journal Articles

Improved experimental methods are discussed for laboratory measurement of conductivity and electric field in insulating spacecraft material intended for space radiation and plasma environments. These measurement techniques investigate the following features: 1) Measurements of conductivity are up to four orders of magnitude smaller than those determined by existing standard methods. 2) Conductivity is altered as radiation accumulates and trapping states fill with electrons. 3) With intense keV electron irradiation, electrons are continually emitted for hours from the irradiated surface after the irradiation ceases. 4) Charging induced by electron irradiation is strongly modified by the electron-hole pairs that the irradiation generates ...


Low Latitude Ionospheric Disturbance Electric Field Effects Duringthe Recovery Phase Of The October 19-21, 1998 Magnetic Storm, Bela G. Fejer, J. T. Emmert Dec 2003

Low Latitude Ionospheric Disturbance Electric Field Effects Duringthe Recovery Phase Of The October 19-21, 1998 Magnetic Storm, Bela G. Fejer, J. T. Emmert

Bela G. Fejer

[1] Low-latitude ionospheric electric fields and currents are often strongly disturbed during periods of enhanced geomagnetic activity. These perturbations can last for several hours after geomagnetic quieting. We use incoherent scatter radar measurements from Jicamarca and Arecibo during 19–21 October 1998 to study, for the first time, the low-latitude disturbance electric fields during the recovery phase of a large magnetic storm. On 19 October the Jicamarca data showed initially large and short-lived (time scale of about 10–20 min) upward and westward drift perturbations in the early afternoon sector, due to the penetration of strong magnetospheric electric fields probably ...


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

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

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

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.


Modelling Growth And Testing Of Multilayer Cavity Structures Incorporating Birefringent Materials, Nour-Eddine El Khachia Dec 2003

Modelling Growth And Testing Of Multilayer Cavity Structures Incorporating Birefringent Materials, Nour-Eddine El Khachia

Masters

A simple one-dimensional photonic bandgap structure, which is also known as a Fabry-Perot Microcavity (FPM) structure was studied theoretically and experimentally. In particular this project addressed introducing an optically birefringent material in the cavity. This FPM consists of two grown regular Distributed Bragg Reflector (DBR) mirrors that can be put together as a sandwich with a space between them, which will lead to the creation of the desired cavity. Each mirror, or one-dimensional dielectric stack structure, was grown using the Vacuum Evaporation Technique and consists of multiple layers of alternating high-and low-refractive index dielectric materials arranged periodically. The project covers ...


Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraft Charging, A. R. Frederickson, Jr Dennison Dec 2003

Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraft Charging, A. R. Frederickson, Jr Dennison

All Physics Faculty Publications

Improved experimental methods are discussed for laboratory measurement of conductivity and electric field in insulating spacecraft material intended for space radiation and plasma environments. These measurement techniques investigate the following features: 1) measurements of conductivity are up to four orders of magnitude smaller than those determined by existing standard methods. 2) Conductivity is altered as radiation accumulates and trapping states fill with electrons. 3) With intense kiloelectronvolt electron irradiation, electrons are continually emitted for hours from the irradiated surface after the irradiation ceases. 4) Charging induced by electron irradiation is strongly modified by the electron-hole pairs that the irradiation generates ...


Physica: The Newsletter Of Utep's Department Of Physics, Utep Department Of Physics Dec 2003

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

The Department of Physics

Electronic newsletter of UTEP's Department of Physics, December 2003.


Charge Transfer In Slow Collisions Of C⁴⁺ With H Below 1 Kev/Amu, Chen-Nan Liu, Anh-Thu Le, C. D. Lin Dec 2003

Charge Transfer In Slow Collisions Of C⁴⁺ With H Below 1 Kev/Amu, Chen-Nan Liu, Anh-Thu Le, C. D. Lin

Physics Faculty Research & Creative Works

We reexamined charge-transfer cross sections for C⁴⁺ + H collisions for energies from 1 meV/amu to 1 keV/amu using the recently developed hyperspherical close-coupling method. Our results agree with several previous theoretical calculations using molecular-orbital expansion. However, these converged theoretical predictions do not agree with total cross sections from the merged-beam experiments.


Midrapidity Neutral-Pion Production In Proton-Proton Collisions At Root S 200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Dec 2003

Midrapidity Neutral-Pion Production In Proton-Proton Collisions At Root S 200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The invariant differential cross section for inclusive neutral-pion production in p+p collisions at root s=200 GeV has been measured at midrapidity (\eta\<0.35) over the range 1 < p(T) less than or similar to 14 GeV/c by the PHENIX experiment at the Relativistic Heavy Ion Collider. Predictions of next-to-leading order perturbative QCD calculations are consistent with these measurements. The precision of our result is sufficient to differentiate between prevailing gluon-to-pion fragmentation functions.


Spatial Frequency Response Of Acrylamide Based Holographic Photopolymer, Raghavendra Jallapuram, Izabela Naydenova, Vincent Toal, Suzanne Martin, Robert Howard Dec 2003

Spatial Frequency Response Of Acrylamide Based Holographic Photopolymer, Raghavendra Jallapuram, Izabela Naydenova, Vincent Toal, Suzanne Martin, Robert Howard

Conference Papers

It has been shown that photopolymers are useful in holographic optical elements [1] and holographic interferometry [2]. However, the list of potential applications increases greatly if reflection holography is possible. Reflection holography requires a material that has the potential to record high spatial frequencies. Here we studied the spatial frequency response of an acrylamide based dye sensitized holographic photopolymer. We have investigated the effect of molecular weight of the binder and concentration of crosslinking monomer on diffusion using real time monitoring of the holographic grating formation. The effect of uniform pre-exposure on diffusion was also investigated. We have also demonstrated ...


Development Of Dose Conversion Coefficients For Radionuclides Produced In Spallation Neutron Sources: Quarterly Progress Report 8/20/03 – 12/01/03, Phillip W. Patton, Mark Rudin Dec 2003

Development Of Dose Conversion Coefficients For Radionuclides Produced In Spallation Neutron Sources: Quarterly Progress Report 8/20/03 – 12/01/03, Phillip W. Patton, Mark Rudin

Transmutation Sciences Physics (TRP)

A research consortium comprised of representatives from several universities and national laboratories has been established as part of this project to generate internal and external dose conversion coefficients for radionuclides produced in spallation neutron sources. Information obtained from this multi-year study will be used to support the siting and licensing of future accelerator-driven nuclear initiatives within the U.S. Department of Energy complex, including the Spallation Neutron Source (SNS) and Accelerator Production of Tritium (APT) Projects. Determination of these coefficients will also fill data gaps for several hundred radionuclides that exist in Federal Guide Report No. 11 and in Publications ...


Lamb Shift Of Laser-Dressed Atomic States, Ulrich D. Jentschura, Jorg Evers, Martin K. Haas, Christoph H. Keitel Dec 2003

Lamb Shift Of Laser-Dressed Atomic States, Ulrich D. Jentschura, Jorg Evers, Martin K. Haas, Christoph H. Keitel

Physics Faculty Research & Creative Works

We discuss radiative corrections to an atomic two-level system subject to an intense driving laser field. It is shown that the Lamb shift of the laser-dressed states, which are the natural state basis of the combined atom-laser system, cannot be explained in terms of the Lamb shift received by the atomic bare states which is usually observed in spectroscopic experiments. In the final part, we propose an experimental scheme to measure these corrections based on the incoherent resonance fluorescence spectrum of the driven atom.


Probing Scattering Wave Functions Close To The Nucleus, Don H. Madison, Daniel Fischer, Matthew S. Foster, Michael Schulz, Robert Moshammer, Stephenie J. Jones, Joachim Hermann Ullrich Dec 2003

Probing Scattering Wave Functions Close To The Nucleus, Don H. Madison, Daniel Fischer, Matthew S. Foster, Michael Schulz, Robert Moshammer, Stephenie J. Jones, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

Recently, three-dimensional imaging of the ejected electrons following 100  MeV/amu C6+ single ionization of helium led to the observation of a new structure not predicted by theory [M. Schulz et al., Nature (London) 422, 48 (2003)]. Instead of the usual “recoil lobe” centered on the momentum-transfer axis, a ring-shaped structure centered on the beam axis was observed. New measurements at 2  MeV/amu exhibit a similar structure, which is now predicted by theory. We argue that the same theory failed at 100  MeV/amu because the faster projectiles probe distances much closer to the nucleus, where our multiple-scattering ...