Physics Commons^™

Search For Higgs Bosons Produced In Association With A Vector Boson In Pp̅ Collisions At √S = 1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We search for Higgs bosons produced in association with a massive vector boson in 91 ± 7 pb^-1 of pp̅ collisions at √s =1.8 TeV recorded by the Collider Detector at Fermilab. We assume the Higgs scalar H⁰ decays to a bb̅ pair with branching ratio β, and we consider the hadronic decays of the vector boson V (W or Z). Observations are consistent with background expectations. We place 95% confidence level upper limits on σ (pp̅→H⁰V) β as a function of the scalar mass (MH⁰) …

Search For The Decays BS0,BD0 → E±Μ± And Pati-Salam Leptoquarks, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have searched for the decays B_s⁰→ e^±μ^± and B_d⁰ → e^±μ^± using a 102 pb^-1 data sample of pp̅ collisions at √s =1.8 TeV collected with the Collider Detector at Fermilab. We set upper limits on the branching fractions of Ɓ(B_s⁰ → e^±μ^±) < 6.1(8.2) X 10^-6 and Ɓ(B_d⁰ → e^±μ^±) < 3.5(4.5) X 10^-6 at 90(95)% confidence level. Using these limits, we set lower bounds on the corresponding Pati-Salam leptoquark masses and find that M_LQ(B …

An Ab Initio Study Of The Mono- And Difluorides Of Krypton, Gerald J. Hoffman, Laura A. Swafford '97, Robert J. Cave

All HMC Faculty Publications and Research

Results from ab initio calculations at the CCSD(T) level of theory are presented for krypton monofluoride (KrF), krypton monofluoride cation (KrF+), linear, ground-state krypton difluoride (KrF2), the triplet state of krypton difluoride, and the krypton–fluorine van der Waals complex (Kr–F2). These are the first calculations demonstrating that KrF is a bound molecule, in agreement with experimental observation. When corrected for basis-set superposition error, the calculated potential displays quantitative agreement with the attractive wall of the experimentally measured potential curve. Results are also presented for KrF+ and linear KrF2 which yield accurate values for their dissociation energies. The triplet state of …

Density Of Zeros On The Lee-Yang Circle Obtained From Magnetization Data Of A Two-Dimensional Ising Ferromagnet, Christian Binek

Christian Binek Publications

In order to provide experimental access to the statistical theory of Lee and Yang [Phys. Rev. 87, 410 (1952)] the density function g(θ) of zeros on the Lee-Yang circle has been determined for the first time by analyzing isothermal magnetization data m(H) of the Ising ferromagnet FeCl₂ in axial magnetic fields H at temperatures 34≤T≤99 K. The validity of our approach is demonstrated by the perfect agreement of magnetic specific heat data as calculated from g(θ) and m(H) via Maxwell's relation. Moreover, the correct in-plane exchange constant of FeCl₂ emerges from the …

Fundamental And Magnetic-Hardening Studies Of Nanocrystalline And Naaocomposite 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.

Experimental Observation Of Relativistic Nonlinear Thomson Scattering, Szu-Yuan Chen, Anatoly Maksimchuk, Donald Umstadter

Donald Umstadter Publications

Classical Thomson scattering—the scattering of low-intensity light by electrons—is a linear process, in that it does not change the frequency of the radiation; moreover, the magnetic-field component of light is not involved. But if the light intensity is extremely high (~10¹⁸ Wcm^–2), the electrons oscillate during the scattering process with velocities approaching the speed of light. In this relativistic regime, the effect of the magnetic and electric fields on the electron motion should become comparable, and the effective electron mass will increase. Consequently, electrons in such high fields are predicted to quiver nonlinearly, moving in figure-eight patterns …

Relativistic Nonlinear Optics, Phillip F. Schewe, Ben Stein, Donald P. Umstadter

Donald Umstadter Publications

Laser light is a convenient way of transporting both electric and magnetic fields. When an electron encounters light, however, it is usually the electric field that does the talking; the magnetic part of light is less influential since its effect on the electron is proportional to the electron's speed as a fraction of the speed of light (c). In new experiments at the University of Michigan this is all changed since the intensity of the laser light used is so great (a terawatt of power, compared to a milliwatt for a laser in a CD player) that the electrons in …

Events With A Rapidity Gap Between Jets In P̅P Collisions At √S = 630 Gev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report a measurement of the fraction of dijet events with a rapidity gap between jets produced by color-singlet exchange in p̅p collisions at √s =630 GeV at the Fermilab Tevatron. In events with two jets of transverse energy E_T^jet > 8 GeV, pseudorapidity in the range 1.8 <|η^jet | < 3.5 and η₁ η₂ < 0, the color-singlet exchange fraction is found to be R=[2.7 ± 0.7(stat) ± 0.6(syst)]%. Comparisons are made with results obtained at √s =1800 GeV and with theoretical expectations.

Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xiii. Ultraviolet Observations Of The Broad-Line Radio Galaxy 3c 390.3, Paul T. O'Brien, M. Dietrich, K. Leighly, D. Alloin, J. Clavel, D. Michael Crenshaw, K. Horne, G. A. Criss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Bradley M. Peterson, G. A. Reichert, P. M. Rodriguez-Pascual, W. Wamsteker, K. S.J. Anderson, N. G. Bochkarev, F.-Z. Cheng, A. V. Filippenko, C. Martin Gaskell, I. M. George, M. R. Goad, L. C. Ho, Shai Kaspi, W. Kollatschny, Kirk T. Korista, G. Macalpine, D. Marlow, P. G. Martin, S. L. Morris, Richard William Pogge, B. C. Qian, M. C. Recondo-Gonzalez, J. M. Rodriguez Espinosa, M. Santos-Lleo, A. I. Shapovalova, J. M. Shull, G. M. Stirpe, W.-H. Sun, T. J. Turner, R. Vio, S. Wagner, I. Wanders, K. A. Wills, H. Wu, S. J. Xue, Z.-L. Zou

C. Martin Gaskell Publications

As part of an extensive multi-wavelength monitoring campaign, the International Ultraviolet Explorer satellite was used to observe the broad-line radio galaxy 3C 390.3 during the period 1994 December 31-1996 March 5. Spectra were obtained every 6È10 days. The UV continuum varied by a factor of 7 through the campaign, while the broad emission lines varied by factors of 2È5. Unlike previously monitored Seyfert 1 galaxies, in which the X-ray continuum generally varies with a larger amplitude than the UV, in 3C 390.3 the UV continuum light curve is similar in both amplitude and shape to the X-ray light curve observed …

Measurement Of Three-Jet Distributions In Photoproduction At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, 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, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi

Faculty Publications

The cross section for the photoproduction of events containing three jets with a three-jet invariant mass of M31 > 50 GeV has been measured with the ZEUS detector at HERA. The three-jet angular distributions are inconsistent with a uniform population of the available phase space but are well described by parton shower models and script O sign(α α2s) pQCD calculations. Comparisons with the parton shower model indicate a strong contribution from initial state radiation as well as a sensitivity to the effects of colour coherence. © 1998 Elsevier Science B.V. All rights reserved.

Static-Electric-Field-Induced, High-Energy Plateau For Scattered X-Ray Photons In Laser-Assisted, X-Ray–Atom Scattering, Dejan B. Miloševic, Anthony F. Starace

Anthony F. Starace Publications

We consider scattering of x rays by H atoms in the presence of both a linearly polarized laser field and a static electric field. Results for the differential cross section as a function of the number of photons n exchanged with the laser field are presented. For x-ray–atom scattering in the presence of a 10¹⁴ W/cm² laser field the differential cross section has a plateau only for emitted photons (n<0). Adding a static electric field gives rise to an extended plateau for absorbed photons (n>0), indicating a substantial increase of the scattered x-ray energies. We present a quasiclassical explanation of these results.

Magnetic Microstructure Of Magnetotactic Bacteria By Electron Holography, Rafal E. Dunin-Borkowski, Martha R. Mccartney, Richard B. Frankel, Dennis A. Bazylinski, Mihály Pósfai, Peter R. Buseck

Physics

Off-axis electron holography in the transmission electron microscope was used to correlate the physical and magnetic microstructure of magnetite nanocrystals in magnetotactic bacteria. The magnetite crystals were all single magnetic domains, and the magnetization directions of small superparamagnetic crystals were constrained by magnetic interactions with larger crystals in the chains. Shape anisotropy was found to dominate magnetocrystalline anisotropy in elongated crystals. A coercive field between 300 and 450 oersted was determined for one chain.

Nonanalytic Magnetization Dependence Of The Magnon Effective Mass In Itinerant Quantum Ferromagnets, Dietrich Belitz, Theodore R. Kirkpatrick, Andrew J. Millis, Thomas Vojta

Physics Faculty Research & Creative Works

The spin-wave dispersion relation in both clean and disordered itinerant quantum ferromagnets is calculated. It is found that effects akin to weak-localization physics cause the frequency of the spin waves to be a nonanalytic function of the magnetization m. For low frequencies Ω, small wave vectors k, and m→0, the dispersion relation is found to be of the form Ω=const x m^1-αk², with α = (4-d)/2 (2 < d < 4) for disordered systems, and α = (3-d) (1 < d < 3) for clean ones. In d = 4 (disordered) and d = 3 (clean), Ωαm ln (1/m) k². Experiments to test these predictions are proposed.

Effect Of Ammonia Flow Rate On Impurity Incorporation And Material Properties Of Si-Doped Gan Epitaxial Films Grown By Reactive Molecular Beam Epitaxy, Wook Kim, A. E. Botchkarev, H. Morkoç, Z-Q. Fang, David C. Look, David J. Smith

Physics Faculty Publications

Effect of ammonia flow rate on the impurity incorporation and material properties of Si-doped GaN films grown by reactive molecular beam epitaxy (RMBE) process is discussed. It appears that the ammonia flow rate has a marginal effect on the incorporation of impurities into the Si-doped GaN films except there was a little decrease in O and Si with increasing ammonia flow rate when the Si concentration in the film is higher than 10¹⁸ cm⁻³. Electron Hall mobility of Si-doped GaN films grown by RMBE varies with ammonia flow rate used during film growth. From deep level transient …

Differences Between Regular And Random Order Of Updates In Damage-Spreading Simulations, Thomas Vojta, Michael Schreiber

Physics Faculty Research & Creative Works

We investigate the spreading of damage in the three-dimensional Ising model by means of large-scale Monte Carlo simulations. Within the Glauber dynamics we use different rules for the order in which the sites are updated. We find that the stationary damage values and the spreading temperature are different for different update order. In particular, random update order leads to larger damage and a lower spreading temperature than regular order. Consequently, damage spreading in the Ising model is nonuniversal not only with respect to different update algorithms (e.g., Glauber vs heat-bath dynamics) as already known, but even with respect to the …

Translational Shape Invariance And The Inherent Potential Algebra, Asim Gangopadhyaya, Jeffrey Mallow, Uday P. Sukhatne

Physics: Faculty Publications and Other Works

For all quantum-mechanical potentials that are known to be exactly solvable, there are two different, and seemingly independent methods of solution. The first approach is the potential algebra of symmetry groups; the second is supersymmetric quantum mechanics, applied to shape-invariant potentials, which comprise the set of known exactly solvable potentials. Using the underlying algebraic structures of Natanzon potentials, of which the translational shape-invariant potentials are a special subset, we demonstrate the equivalence of the two methods of solution. In addition, we show that, while the algebra for the general Natanzon potential is so(2,2), the subgroup so(2,1) suffices for the shape …

Analysis Of Doubly Excited State Resonances Below The Li(5p) Threshold In Li- Photodetachment, Chien-Nan Liu, Anthony F. Starace

Anthony F. Starace Publications

Larger scale eigenchannel R-matrix calculations than those of Pan et al.  [Phys. Rev. A53, 840 (1996)] confirm the prediction of a 2-meV-wide resonance feature at a photon energy of 5.421 eV in the Li (3s) partial cross section resulting from photodetachment of Li^-. This resonance was neither clearly observed nor identified in measurements of Ljungblad et al. [Phys. Rev. Lett. 77, 3751 (1996)]. We identify this resonance as a _N{υ}_n^A=₅{1}₆^- state [having angular symmetry (K,T)^A=(2,0) ^- or (n …

Excitation Efficiency Of A Morphology-Dependent Resonance By A Focused Gaussian Beam, James A. Lock

Physics Faculty Publications

The excitation efficiency of a morphology-dependent resonance (MDR) by an incident beam is defined as the fraction of the beam power channeled into the MDR. The efficiency is calculated for a focused Gaussian beam of arbitrary width incident on either a spherical particle or a cylindrical fiber located at an arbitrary position in the plane of the beam waist. In each case a simple formula for the efficiency is derived by use of the localized approximation for the beam-shape coefficients in the partial-wave expansion of the beam. The physical interpretation of the efficiency formulas is also discussed. (C) 1998 Optical …

Relaxational Mode Structure For Optical Probe Diffusion In High Molecular Weight Hydroxypropylcellulose, Kiril A. Streletzky, George D.J. Phillies

Physics Faculty Publications

We studied translational diffusion of dilute monodisperse spheres (diameters 14 < d < 455 nm) in aqueous 1 MDa hydroxypropylcellulose (0 ≤ c ≤ 7 g/L) at 25°C using quasielastic light scattering. Spectra are highly bimodal. The two spectral modes (“slow,” “fast”) have different physical properties. Probe behavior differs between small (d < Rh) and large (d ≥ Rg) probes; Rh and Rg are the matrix polymer hydrodynamic radius and the radius of gyration, respectively. We examined the dependences of spectral lineshape parameters on d, c, scattering vector q, and viscosity η for all four probe-size and mode-type combinations. We find three time scale-separated modes: (1) a large-probe slow mode has properties characteristic of particle motion in a viscous medium; (2) a large-probe fast mode and small-probe slow modes share the same time scale, and have properties characteristic of probe motion coupled to internal chain dynamics; and (3) a small-probe fast mode has properties that can be attributed to the probe sampling local chain relaxations. In the analysis, we also attempted to apply the coupling/scaling (CS) model of Ngai and Phillies [Ngai, K. L., Phillies, G. D. J. J. Chem. Phys.,105, 8385 (1996)] to analyze our data. We find that the second mode is described by the coupling/scaling model for probe diffusion; the first and third modes do not follow the predictions of this model.

Collisional Effects In The Absorption Spectra Of The Oxygen A Band And Nitric Oxide Fundamental Band, Robert S. Pope

Theses and Dissertations

Fourier transform spectroscopy was used to measure pressure broadening coefficients in the absorption spectra of both the oxygen A band and the nitric oxide fundamental band. Oxygen spectra were recorded with O₂, N₂, CO, CO₂, SF₆ and noble gas collision partners, while nitric oxide spectra were recorded using noble gas collision partners. Pressure broadening coefficients were determined in the P and R branches for every resolved line for each of the fifteen collision pairs studied. In addition, broadening coefficients and qualitative evidence of line coupling were found for the Q branch of NO …

Production Of Bound Μ⁺Μˉ Systems In Relativistic Heavy Ion Collisions, Ilya F. Ginzburg, Ulrich D. Jentschura, Savely Karshenboim, Frank Krauss, Valery G. Serbo, Gerhard Soff

Physics Faculty Research & Creative Works

Dimuonium (the bound system of two muons, the μ⁺ μ^--atom system) has not been observed yet. In this paper we discuss the electromagnetic production of dimuonium at RHIC and LHC in relativistic heavy ion collisions. The production of parastates is analyzed in the equivalent photon approximation. For the treatment of orthostates, we develop a three-photon formalism. We determine the production rates at RHIC and LHC with an accuracy of a few percent and discuss problems related to the observation of dimuonium.

Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos

Dartmouth Scholarship

We study the conditions under which an overdamped regime can be attained in the dynamic evolution of a quantum field configuration. Using a real-time formulation of finite temperature field theory, we compute the effective evolution equation of a scalar field configuration, quadratically interacting with a given set of other scalar fields. We then show that, in the overdamped regime, the dissipative kernel in the field equation of motion is closely related to the shear viscosity coefficient, as computed in scalar field theory at finite temperature. The effective dynamics is equivalent to a time-dependent Ginzburg-Landau description of the approach to equilibrium …

Batelaan And Gay Reply, Herman Batelaan, Timothy J. Gay

Timothy J. Gay Publications

In their Comment [1] to our Letter [2], Rutherford and Grobe first disagree with our conclusion that “a tabletop Stern-Gerlach filter is feasible.” Given our estimate of the throughput for such a device, ~0.3 electrons/s, we were clearly not proposing it as an alternative to standard polarized electron sources (~10¹⁵ electrons/s). The main argument for “feasibility” is based on the relatively low currents required to establish the solenoidal magnetic field (5 A)—hence the use of the word “tabletop” in the abstract. In retrospect, a better statement would have been that “experimental demonstration of such a spin-splitting effect may be …

Insulator-Metal Crossover Near Optimal Doping In Pr22xcexcuo4: Anomalous Normal-State Low Temperature Resistivity, P. Fournier, P. Mohanty, E. Maiser, S. Darzens, T. Venkatesan, C. J. Lobb, G. Czjzek, Richard A. Webb, R. L. Greene

Faculty Publications

Normal-state resistivity measurements at high fields and low temperatures in electron-doped Pr_2-xCe_xCuO₄ thin films reveal an insulator-metal crossover near a doping level x≈0.15, similar to a previous report on hole-doped La_2-xSr_xCuO₄. The temperature dependence of the resistivity of insulatinglike samples is sublogarithmic, while for metallic samples (with x = 0.17) the resistivity is linear from 40 mK to 40 K. This surprising latter observation suggests an unusual contribution to the scattering processes at low temperature in these materials. We conclude that the ground state at x = 0.15, corresponding …

Laser Cooling And Trapping Of Argon Metastable Atomic Beam, Juan Carlos Catala

FIU Electronic Theses and Dissertations

The high velocity of free atoms associated with the thermal motion, together with the velocity distribution of atoms has imposed the ultimate limitation on the precision of ultrahigh resolution spectroscopy. A sample consisting of low velocity atoms would provide a substantial improvement in spectroscopy resolution.

To overcome the problem of thermal motion, atomic physicists have pursued two goals; first, the reduction of the thermal motion (cooling); and second, the confinement of the atoms by means of electromagnetic fields (trapping). Cooling carried sufficiently far, eliminates the motional problems, whereas trapping allows for long observation times.

In this work the laser cooling …

Laser-Plasma Harmonics With High-Contrast Pulses And Designed Prepulses, R.S. Marjoribanks, L. Zhao, F.W. Budnik, G. Kulcsar, A. Vitcu, H. Higaki, R. Wagner, Anatoly Maksimchuk, Donald P. Umstadter, S.P. Le Blanc, M.C. Downer

Donald Umstadter Publications

One aspect of the complexity of mid- and high-harmonic generation in highintensity laser-plasma interactions is that nonlinear hydrodynamics is virtually always folded together with the nonlinear optical conversion process. We have partly dissected this issue in picosecond and subpicosecond interactions with preformed plasma gradients, imaging and spectrally resolving low- and mid-order harmonics. We describe spatial breakup of the picosecond beam in preformed plasmas, concomitant broaden~ng and breakup of the harmonic spectrum. presumably through self-phase modulation, together with data on the sensitivity of harmonics production efficiency to the gradient or extent of prefomed plasma. Lastly. we show preliminary data of regular …

Development Of A Generalized Theoretical Model For The Response Of A Phase/Doppler Measurement System To Arbitrarily Oriented Fibers Illuminated By Gaussian Beams, Scott A. Schaub, James A. Lock, Amir A. Naqwi

Physics Faculty Publications

We present a generalized theoretical model for the response of the phase/Doppler (P/D) measurement system to light scattered by cylindrical fibers. This theoretical model is valid for arbitrary fiber diameters and refractive indices, for Gaussian incident beams, and it accounts for arbitrary fiber orientations, fiber positions, and effects that are due to the two-dimensional receivers. The generalized P/D computer model (GPDCM) is the extension of an earlier study by the authors, combining past P/D simulation methodology with recent developments in modeling light scattering by tilted cylindrical fibers. A FORTRAN computer program that implements the GPDCM theoretical development was written and …

U-Duality, D-Branes And Black Hole Emission Rates: Agreements And Disagreements, Fay Dowker, David Kastor, Jennie Traschen

David Kastor

An expression for the spacetime absorption coefficient of a scalar field in a five dimensional, near extremal black hole background is derived, which has the same form as that presented by Maldacena and Strominger, but is valid over a larger, U-duality invariant region of parameter space and in general disagrees with the corresponding D-brane result. We develop an argument, based on D-brane thermodynamics, which specifies the range of parameters over which agreement should be expected. For neutral emission, the spacetime and D-brane results agree over this range. However, for charged emission, we find disagreement in the `Fat Black Hole' regime, …

Sputter Deposition Of High Resistivity Boron Carbide, Ahmad A. Ahmad, Natale J. Ianno, Seong-Don Hwang, Peter A. Dowben

Peter Dowben Publications

We have succeeded in the rf magnetron sputter deposition of high resistivity boron carbide (B1−xCx). This has been accomplished by the sputter depositing the boron carbide from a methane saturated boron carbide target. We show that the composition and optical band gap of the sputter deposited material are functions of the applied rf power. Furthermore, boron carbide/silicon heterojunction diodes fabricated via sputtering compare favorably with those fabricated from borane cage molecule sources using plasma enhanced chemical vapor deposition (PECVD).

Black Holes With Magnetic Charge And Quantized Mass, A. Yu. Ignatiev, G. C. Joshi, Kameshwar C. Wali

Physics - All Scholarship

We examine the issue of magnetic charge quantization in the presence of black holes. It is pointed out that quantization of magnetic charge can lead to the mass quantization for magnetically charged black holes. We also discuss some implications for the experimental searches of magnetically charged black holes.