Physical Sciences and Mathematics Commons^™

Inclusive Decays B->Dx And B->D*X, L. Gibbons, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

We report new measurements of the differential and total branching ratios for inclusive B decay to D-0, D+, and D*+ and the first measurement of the same quantities for inclusive B decay to D-*0. Here B is the mixture of B-d and B-u from Y(4S) decay. Furthermore, since more than one charm particle (or antiparticle) of the same kind can be produced in B decay, here ''inclusive B branching ratio'' is used to mean the average number of charm particles and their antiparticles of a certain species: produced in B decay. We obtain the following results (the first error is …

Shock Waves In Nonequilibrium Gases And Plasmas, William M. Hilbun

Theses and Dissertations

An analysis and assessment of three mechanisms describing plasma/shock wave interactions was conducted under conditions typically encountered in a weakly ionized glow discharge. The mechanisms of ion-acoustic wave damping, post-shock energy addition and thermal inhomogeneities were examined by numerically solving the Euler equations with appropriate source terms adapted for each mechanism. Ion-acoustic wave damping was examined by modeling the partially ionized plasma as two fluids in one spatial dimension using the Riemann problem as a basis. Post-shock energy addition in the form of nonequilibrium vibrational energy relaxation was also examined in one spatial dimension using the Riemann problem as a …

Aspects Of Postcollision Interactions (Pci) Near The Ar L-Shell, James A.R. Samson, Y. Lu, Wayne C. Stolte

Chemistry and Biochemistry Faculty Research

In the present work we are interested in near-threshold photoionization experiments involving postcollision effects related to the Auger decay of a vacancy in the Ar L shell. In particular, we have measured the photoelectron energy spectrum resulting from the above postcollision interaction effects and have observed electrons produced by the process of electron capture and reemission.

System For Electron Paramagnetic Resonance Measurements At High Pressure And Low Temperature, Ke Huang, Daniel L. Decker, H. Mark Nelson, J. Dean Barnett

Faculty Publications

Major improvements have been made on the sensitive high pressure electron paramagnetic resonance (EPR) system developed previously in 1978 at this laboratory. These changes allow low temperature measurements and provide a more stable signal. The high pressure EPR cell is placed inside a vacuum chamber to provide thermal isolation, so that the system may be cooled by a closed cycle refrigerator to temperatures between 45 and 60 K, depending on the energy input to the modulation coil. The combination of high pressure and low temperature greatly expands the thermodynamic range over which EPR measurements can be made. An improved and …

Selective Cvd Growth Of Diamond Crystals On Tungsten, Charles Randal Cole

Electrical & Computer Engineering Theses & Dissertations

Typical field emitters consist of sharp metal tips which usually have a short life due to erosion and contamination. To improve the performance of regular field emitters, diamond can be placed on the emitter tip. This is done by selectively growing diamond on tungsten tips using chemical vapor deposition (CVD) processing. Diamond exhibits negative electron affinity, so that electrons will be emitted by properly biasing the tip.

To obtain single crystal growth right at the tip, a cantilever controlled nucleation method was developed which worked better than other methods. Surface preparation was also important to the growth process. An oxide …

First Observation Of Τ→3ΠηνΤ And Τ→ F1ΠνΤ Decays, T. Bergfeld, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have observed new channels for τ decays with an η in the final state. We study 3-prong tau decays, using the η →γγ and η → 3π ⁰ decay modes and 1-prong decays with two π ⁰’s using the η →γγ channel. The measured branching fractions are B(τ^- → π^-π^-π⁺ην_τ) = (3. _-0.5^+0.6 ± 0.6) X 10^-4 and B(τ^- → π^-2π ⁰ην_τ) = (1.4 ± 0.6 ± 0.3) X 10^-4. We observe clear evidence for f_{1 …}

Single-Shot Detection Of Wavepacket Evolution, M. B. Campbell, Thomas J. Bensky, Robert R. Jones

Physics

We have developed a new instrument for monitoring electronic wavepacket dynamics using a single electromagnetic pulse pair. The operation of the device is analogous to that of single-shot cross-correlators commonly used to monitor the temporal evolution of short laser pulses. We have used the instrument to probe wavepacket evolution over time scales ranging from 100 psec to less than 1 fsec. The device reduces the amount of time required to collect pump-probe time delay data by orders of magnitude, greatly reducing the deleterious effects of experimental drifts. In addition, the single-shot feature provides real-time feedback as to the affect of …

Effects Of Self-Avoidance On The Tubular Phase Of Anisotropic Membranes, Mark Bowick, Emmanuel Guitter

Physics - All Scholarship

We study the tubular phase of self-avoiding anisotropic membranes. We discuss the renormalizability of the model Hamiltonian describing this phase and derive from a renormalization group equation some general scaling relations for the exponents of the model. We show how particular choices of renormalization factors reproduce the Gaussian result, the Flory theory and the Gaussian Variational treatment of the problem. We then study the perturbative renormalization to one loop in the self-avoiding parameter using dimensional regularization and an epsilon-expansion about the upper critical dimension, and determine the critical exponents to first order in epsilon.

Crossover Dynamics For Polymer Simulation In Porous Media, V. Yamakov, D. Stauffer, A. Milchev, G.M. Foo, R.B. Pandey

Faculty Publications

Off-lattice Monte Carlo simulations show anomalous diffusion at intermediate times without a clear Rouse regime, for the motion of chains through a random porous medium.

Locally Optimally Emitting Clouds And The Narrow Emission Lines In Seyfert Galaxies, Jason W. Ferguson, Kirk T. Korista, Jack A. Baldwin, Gary J. Ferland

Physics and Astronomy Faculty Publications

The narrow emission line spectra of active galactic nuclei are not accurately described by simple photoionization models of single clouds. Recent Hubble Space Telescope images of Seyfert 2 galaxies show that these objects are rich with ionization cones, knots, filaments, and strands of ionized gas. Here we extend to the narrow-line region the ``locally optimally emitting cloud'' (LOC) model, in which the observed spectra are predominantly determined by powerful selection effects. We present a large grid of photoionization models covering a wide range of physical conditions and show the optimal conditions for producing many of the strongest emission lines. We …

Singular Structure In 4d Simplicial Gravity, Simon Catterall, R. Renken, John B. Kogut

Physics - All Scholarship

We show that the phase transition previously observed in dynamical triangulation models of quantum gravity can be understood as being due to the creation of a singular link. The transition between singular and non-singular geometries as the gravitational coupling is varied appears to be first order.

Ionization Of Na Rydberg Atoms By Subpicosecond Quarter-Cycle Circularly Polarized Pulses, Thomas J. Bensky, G. Haeffler, Robert R. Jones

Physics

We report the first observation of ionization of Rydberg atoms by subpicosecond, circularly polarized THz radiation. The field amplitude in these pulses is non-negligible for only one-quarter of an optical cycle. The experiment is performed in the short-pulse regime, where the duration of the ionizing pulse is shorter than the classical Kepler period of the Rydberg electron. We find that the ionization probability for these atoms is remarkably insensitive to the time-varying polarization of the THz field.

Inclination Effects In Spiral Galaxy Gravitational Lensing, Ariyeh Maller, Ricardo Flores, Joel Primack

Physics Faculty Works

Spheroidal components of spiral galaxies have been considered to be the only dynamically important component in gravitational lensing studies to date. Here we point out that including the disk component can have a significant effect, which depends on the disk inclination, on a variety of lensing properties that are relevant to present studies and future surveys. As an example, we look at the multiple image system B1600+434, which was recently identified as being lensed by a spiral galaxy. We find that by including the disk component, one can understand the fairly large image separation as being caused by the inclination …

Statistical Topography Of Glassy Interfaces, Alan Middleton, Chen Zeng, Jane Kondev, David Mcnamara

Physics - All Scholarship

Statistical topography of two-dimensional interfaces in the presence of quenched disorder is studied utilizing combinatorial optimization algorithms. Finite-size scaling is used to measure geometrical exponents associated with contour loops and fully packed loops. We find that contour-loop exponents depend on the type of disorder (periodic ``vs'' non-periodic) and they satisfy scaling relations characteristic of self-affine rough surfaces. Fully packed loops on the other hand are unaffected by disorder with geometrical exponents that take on their pure values.

Electron-Collision-Induced Alignment Of Rare Gases Near Threshold, V. Zeman, K. Bartschat, Timothy J. Gay, K. W. Trantham

Timothy J. Gay Publications

Results of a semirelativistic R-matrix calculation are compared with experimental values for light polarizations and alignment parameters of the second excited-state manifolds of neon and krypton following electron impact excitation. The calculations focus on the near-threshold regime, where negative-ion resonances have a significant effect on the atomic alignment. A grouping of the alignment values according to the electronic angular momentum J of the excited state is observed and qualitatively explained by angular momentum coupling considerations.

Measurement Of The Proton Structure Function F2 And ΣΓ*ΡTot At Low Q2 And Very Low X 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, E. Anselmo, R. 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

A small electromagnetic sampling calorimeter, installed in the ZEUS experiment in 1995, significantly enhanced the acceptance for very low x and low Q2 inelastic neutral current scattering, e+p → e+X, at HERA. A measurement of the proton structure function F2 and the total virtual photon-proton (γ*p) cross-section is presented for 0.11 ≤ Q2 ≤ 0.65 GeV2 and 2 × 10-6 ≤ x ≤ 6 × 10-5, corresponding to a range in the γ*p c.m. energy of 100 ≤ W ≤ 230 GeV. Comparisons with various models are also presented. © 1997 Published by Elsevier Science B.V.

D* Production In Deep Inelastic Scattering 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, R. 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

This paper presents measurements of D*f± production in deep inelastic scattering from collisions between 27.5GeV positrons and 820GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel D*+ → (D0 → K-π+)π+ (+c.c.) has been used in the study. The e+p cross section for inclusive D*± production with 5 < Q2 < 100GeV2 and y < 0.7 is 5.3±1.0±0.8nb in the kinematic region 1.3 < pT(D*±) < 9.0GeV and |η(D*±) | < 1.5. Differential cross sections as functions of pT(D*±), η(D*±), W and Q2 are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in pT(D*±) and η(D*±), the charm contribution Fcc̄2(x,Q2) to the proton structure function is determined for Bjorken x between 2 · 10-4 and 5 · 10-3. © 1997 Elsevier Science B.V.

Fluctuation Properties Of Precipitation. Part I: On Deviations Of Single-Size Drop Counts From The Poisson Distribution, Alexander Kostinski, A. R. Jameson

Department of Physics Publications

The traditional statistical description of the spatial and temporal distributions of cloud droplets and raindrops is the Poisson process, which tends to place the drops as uniformly as randomness allows. Yet, the “clumpy” nature of clouds and precipitation is apparent to most casual observers and well known to cloud physicists. Is such clumpiness consistent with the Poisson statistics? The authors explore the possibility of deviations from the Poisson distribution using temporal raindrop counting experiments. Disdrometer measurements during the passage of a squall line strongly indicate that a mixture of Poisson distributions (Poisson mixture) provides a better description of the frequency …

High Coercivity Smfealc Thin Films Fabricated By Multilayer Sputtering, M.L. Yan, Z.S. Shan, Yi Liu, David J. Sellmyer

David Sellmyer Publications

Multilayer sputtering of SmFe/C(Al) plus appropriate thermal processing has been used to fabricate SmFeC thin films with A1 substitution for Fe. It was found that the SmFeAlC thin films exhibited exceptionally high Coercivities. A coercivity of 28 kOe was realized for the thin film with structure of Ta(l000 Å)/|SmFe(40Å)/ C(Al)(5Å)]x50/Ta(200Å) with subsequent annealing at 650°C.

Magnetic And Structural Properties Of Sm2Fe10Co7/MXCY Thin Films, I.A. Al-Omari, N. J. Cunningham, David J. Sellmyer

David Sellmyer Publications

The structural and magnetic properties of Sm₂Fe₁₀Co₇/M_xC_y (M=A1 and Si; x≥0 and y≥0) multilayer films with Ta underlayers and overlayers before and after annealing at 700 °C for 5-12 min have been fabricated and studied. Structural studies show evidence of layer diffusion upon annealing. X-ray diffraction shows that the samples after annealing consist of a soft phase, α -Fe, and a hard phase with the 2-17-type structure. The samples studied have in-plane anisotropy with single hysteresis loops indicating that the two phases are strongly exchange coupled. After annealing, the coercivity of …

“Atomic Processes In High Energy Density Plasmas," Summaries Of Fy 1997 Research In The Chemical Sciences, Donald P. Umstadter

Donald Umstadter Publications

Several important plasma atomic processes are studied in a controlled manner. These studies are enabled by the recent invention of ultrashortpulse- duration lasers, which produce plasmas with independently controllable parameters.

Segregation Of Bismuth To Triple Junctions In Copper, K.-M. Yin, Alexander H. King, T.E. Hsieh, F.-R. Chen, J.J. Kai, L. Chang

Alexander H. King

Bismuth segregation in copper has been studied using energy-dispersive X-ray spectrometry (EDX) in a JEOL 2010F transmission electron microscope. In addition to the expected solute enrichment at grain boundaries, we have observed extremely high concentrations of bismuth at certain triple junctions, with significantly greater enrichment factors than in the adjacent grain boundaries. It is shown here that the triple junction segregation is a function of the parameters of the grain boundaries at the triple line, and existence of this type of segregation implies that the affected triple junctions embody excess free energy. At least one of the observed triple junctions …

Vibrational Spectra In Ordered And Disordered Ni3al, Jeffrey D. Althoff, Dane Morgan, Didier De Fontaine, Mark Asta, S. M. Foiles, Duane D. Johnson

Duane D. Johnson

We calculate the vibrational density of states (DOS) and corresponding thermodynamic properties of L12 ordered and disordered Ni3Al in the quasiharmonic approximation using the embedded-atom method. Vibrational and thermodynamic properties, including vibrational entropy differences between ordered and disordered states, are found to be in good agreement with experiment. The DOS of the configurationally disordered alloy resembles a broadened version of the DOS of the L12 phase, not a one-atom per cell fcc DOS, and is shifted downward in frequency because the disordered state has a larger volume than the ordered phase. Calculations of the projected DOS indicate that high-frequency modes …

Solitary Waves And Atomic Population Transfer Via The Continuum, Foek T. Hioe, C. E. Carroll

Physics Faculty/Staff Publications

Exact analytic results are presented that represent a pair of solitary waves that can propagate through an atomic medium with their shapes invariant while producing transfer of atoms or molecules from one bound state to another via a continuum. The speed of the waves and the amount of population transfer are given in terms of the wave amplitudes. A general ~not solitary wave! solution for the case of a single wave is presented, together with a nonlinear Beer’s law of absorption.

Hydrocarbon Ions In The Ionosphere Of Titan, Jane L. Fox, Roger V. Yelle

Physics Faculty Publications

We have constructed a new model of the ionosphere of Titan that includes 67 species and 626 reactions. Although N₂⁺ is the major ion produced over most of the ionosphere, the ionization flows to ions whose parent neutrals have lower ionization potentials and to ions formed from species with large proton affinities. In contrast to other models, which have predicted that HCNH⁺ should be the major ion, our calculations suggest that the major ions at and below the ion peak are hydrocarbon ions, and H, C, and N-containing ions. Our predicted peak electron density for a solar …

High Quality Interfaces In Gaas-Alas Quantum Wells Determined From High Resolution Photoluminescence, D. C. Reynolds, David C. Look, B. Jogai, R. Kaspi, K. R. Evans, M. Estes

Physics Faculty Publications

No abstract provided.

A Football Chase On Video, Norman F. Derby, Robert Fuller, Thomas A. Summers

Robert G. Fuller Publications

At some universities, football examples are used to motivate students in physics courses to study the law of kinematics and collisions. (In fact, it has been rumored that the number of such examples is inversely related the national ranking of the local football team.) In addition, pursuit-and-evasion strategies are often introduced in beginning calculus courses as a device for teaching mathematical modeling and problem solving. Some recent papers describe theoretical strategies for pursuit-and-evasion that are appropriate for a one-on-one situation in a football game. But what do players actually do in a real football game? We decided to look into …

Quantum Coulomb Glass Within A Hartree-Fock Approximation, Frank Epperlein, Michael Schreiber, Thomas Vojta

Physics Faculty Research & Creative Works

We study the influence of electron-electron interactions on the electronic properties of disordered materials. In particular, we consider the insulating side of a metal-insulator transition where screening breaks down and the electron-electron interaction remains long ranged. The investigations are based on the quantum Coulomb glass, a generalization of the classical Coulomb glass model of disordered insulators. The quantum Coulomb glass is studied by decoupling the Coulomb interaction by means of a Hartree-Fock approximation and exactly diagonalizing the remaining localization problem. We investigate the behavior of the Coulomb gap in the density of states when approaching the metal-insulator transition and study …

Remanence Enhancement And Exchange Coupling In Prco/Co Films, J. Ping Liu, Yi Liu, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

PrCo/Co multilayer thin films have been prepared by sputtering. After heat treatment, high coercivity is developed and the remanence is enhanced for the insertion of the CO layers and the exchange coupling between the hard phase and the soft phase, which leads to high energy products of the composite magnets. The nanostructure of the films has been studied by TEM. It is found that the grain size of the films with high energy products is in the range from 10 to 25 nanometers.

Defect Donor And Acceptor In Gan, David C. Look, D. C. Reynolds, Joseph W. Hemsky, J. R. Sizelove, R. L. Jones, Richard J. Molnar

Physics Faculty Publications

No abstract provided.