Physics Commons^™

Measurement Of Diffractive Photoproduction Of Vector Mesons At Large Momentum Transfer At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, 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

Faculty Publications

No abstract provided.

Angular And Current-Target Correlations In Deep Inelastic Scattering At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, 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

Faculty Publications

Correlations between charged particles in deep inelastic e+ p scattering have been studied in the Breit frame with the ZEUS detector at HERA using an integrated luminosity of 6.4pb-1. Short-range correlations are analysed in terms of the angular separation between current-region particles within a cone centred around the virtual photon axis. Long-range correlations between the current and target regions have also been measured. The data support predictions for the scaling behaviour of the angular correlations at high Q2 and for anti-correlations between the current and target regions over a large range in Q2 and in the Bjorken scaling variable x. …

Measurement Of High-Q2 Charged-Current E+P Deep Inelastic Scattering Cross Sections At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, 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

Faculty Publications

The e+p charged-current deep inelastic scattering cross sections, dσ/dQ2 for Q2 between 200 and 60000 GeV2, and dσ/dx and dσ/dy for Q2 > 200 GeV2, have been measured with the ZEUS detector at HERA. A data sample of 47.7 pb-1, collected at a center-of-mass energy of 300 GeV, has been used. The double-differential cross-section dσ/dQ2 falls by a factor of about 50000 as Q2 increases from 280 to 30000 GeV2. The double differential cross section d2σ/dxdQ2 has also been measured. A comparison between the data and Standard Model (SM) predictions shows that contributions from antiquarks (ū and c̄) and quarks (d …

Series Operation Of Direct Current Xenon Chloride Excimer Sources, Ahmed El-Habachi, Wenhui Shi, Mohamed Moselhy, Robert H. Stark, Karl H. Schoenbach

Bioelectrics Publications

Stable, direct current microhollow cathode discharges in mixtures of hydrochloric acid, hydrogen, xenon, and neon have been generated in a pressure range of 200–1150 Torr. The cathode hole diameter was 250 μm. Sustaining voltages range from 180 to 250 V at current levels of up to 5 mA. The discharges are strong sources of xenon chloride excimer emission at a wavelength of 308 nm. Internal efficiencies of approximately 3% have been reached at a pressure of 1050 Torr. The spectral radiant power at this pressure was measured as 5 mW/nm at 308 nm for a 3 mA discharge. By using …

Measurements Of Electronic Properties Of Conducting Spacecraft Materials With Application To The Modeling Of Spacecraft Charging, W. Y. Chang, Jr Dennison, Parker Judd

Conference Proceedings

Many spacecraft system anomalies and component failures are known to result from spacecraft charging which is due to the bombardments of spacecraft by energetic electrons, ions, and photons in natural space surrounding [Hastings and Garrett, 1996; Bedingfield et al., 1996; Leach et al., 1995]. To assist spacecraft designers in accommodating and mitigating the harmful charging effects on spacecraft, NASA has developed an extensive set of engineering tools to predict the extent of charging in various spacecraft environments (for example, NASCAP/LEO, NASCAP/GEO, and POLAR) [Mandell et al., 1993]. However, current NASCAP databases lack electronic properties …

Inception Of Snapover And Gas Induced Glow Discharges, J. T. Galofaro, B V. Vayner, D C. Ferguson, C D. Thomson, Jr Dennison, R E. Davies

Conference Proceedings

Ground based experiments of the snapover phenomenon were conducted in the large vertical simulation chamber at the Glenn Research Center (GRC) Plasma Interaction Facility (PIF). Two Penning sources provided both argon and xenon plasmas for the experiments. The sources were used to simulate a variety of ionospheric densities pertaining to a spacecraft in a Low Earth Orbital (LEO) environment^1–4. Secondary electron emission is believed responsible for dielectric surface charging, and all subsequent snapover phenomena observed^2,5. Voltage sweeps of conductor potentials versus collected current were recorded in order to examine the specific charging history of each sample. …

Inception Of Snapover And Gas Induced Glow Discharges, J. T. Galofaro, B V. Vayner, W A. Degroot, D C. Ferguson, C D. Thomson, Jr Dennison, R E. Davies

Conference Proceedings

Ground based experiments of the snapover phenomenon were conducted in the large vertical simulation chamber at the Glenn Research Center (GRC) Plasma Interaction Facility (PIF). Two Penning sources provided both argon and xenon plasmas for the experiments. The sources were used to simulate a variety of ionospheric densities pertaining to a spacecraft in a Low Earth Orbital (LEO) environment^1-4. Secondary electron emission is believed responsible for dielectric surface charging, and all subsequent snapover phenomena observed^2,5. Voltage sweeps of conductor potentials versus collected current were recorded in order to examine the specific charging history of each sample. …

Evolution Of Secondary Electron Emission Characteristics Of Spacecraft Surfaces: Importance To Spacecraft Charging, R. E. Davies, Jr Dennison

Journal Articles

Secondary electron emission (SEE) plays a key role in spacecraft charging [Garrett, 1981; Frooninckx and Sojka, 1992] . As a result, spacecraft charging codes require knowledge of the SEE characteristics of various materials in order to predict vehicle potentials in various orbital environments [Katz, et. al., 1986]. Because SEE is a surface phenomenon, occurring in the first few atomic layers of a material, the SEE characteristics of a given surface are extremely sensitive to changes in surface condition—e.g., the addition or removal of surface contaminants, or changes in surface morphology. That spacecraft surfaces …

Critical Adsorption On Defects In Ising Magnets And Binary Alloys, Andreas Hanke

Physics and Astronomy Faculty Publications and Presentations

Long-range correlations in a magnet close to its critical point or in a binary alloy close to a continuous order-disorder transition can substantially enhance the effect of local perturbations. It is demonstrated using a position-space renormalization procedure that quasi-one-dimensional defects which break the symmetry of the order parameter have pronounced effects: They cause long-range critical adsorption profiles and give rise to new universal critical exponents, which are identified and calculated using field-theoretical methods.

Production Of A Signal By Irradiated Cells Which Leads To A Response In Unirradiated Cells Characteristic Of Initiation Of Apoptosis, Fiona Lyng, C. Seymour, C. Mothersill

Articles

This study investigated the ability of medium from irradiated cells to induce early events in the apoptotic cascade, such as mobilization of intracellular calcium, loss of mitochondrial membrane potential and increase in reactive oxygen species, in cells which were never exposed to radiation. Medium from irradiated human keratinocytes was harvested and transferred to unirradiated keratinocytes. Endpoints characteristic of the initiation of apoptosis were monitored for a period of 24 h following medium transfer. Clonogenic survival was also measured. Rapid calcium fluxes (within 30 s), loss of mitochondrial membrane potential, increases in reactive oxygen species (from 6 h after medium transfer), …

Quantum-Well Resistivity For Perpendicular Transport In Magnetic Layered Systems, Evgeny Y. Tsymbal, David G. Pettifor

Evgeny Tsymbal Publications

We show that quantum-well states enhance the current-perpendicular-to-planes resistivity of a metal film compared to the resistivity in the bulk at film thicknesses comparable with the mean free path due to the reduced number of conducting channels within the potential-well structure. This makes the mean free path an important parameter, which must be taken into account for the accurate treatment of results on currentperpendicular- to-plane giant magnetoresistance, rather than ignored by applying the two-current series-resistor model.

Track Theory Predictions For Single-Hit Cell Survival, Robert Katz, Francis Cucinotta

Robert Katz Publications

The track theory of cell survival after heavy-ion irradiation is based on the probability of survival after a single-particle transit, called ‘‘ion-kill’’ (not track core), joined to the cumulative effect of δ rays from adjacent ions in a beam, called ‘‘gamma-kill’’ (not penumbra). The model offers a set of equations containing four parameters, E₀ and m for the single-hit multitarget statistical model for gamma-kill, and additionally σ₀ and κ for ion-kill. A single set of parameters is used to fit a family of survival curves obtained with ions of different LET simultaneously.

Measurement Of D*± Production And The Charm Contribution To F2 In Deep Inelastic Scattering At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, 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

Faculty Publications

The production of D*± (2010) mesons in deep inelastic scattering has been measured in the ZEUS detector at HERA using an integrated luminosity of 37 pb-1. The decay channels D*+ → D0π+ (+c.c.), with D0 → K-π+ or D0 → K-π-π+π+, have been used to identify the D mesons. The e+p cross section for inclusive D*± production with 1 < Q2 < 600 GeV2 and 0.02 < y < 0.7 is 8.31±0.31(stat.)+0.30-0.50 (syst.) nb in the kinematic region 1.5 < pT(D*±) < 15 GeV and \η(D*±)\ < 1.5. Differential cross sections are consistent with a next-to-leading-order perturbative-QCD calculation when using charm-fragmentation models which take into account the interaction of the charm quark with the proton remnant. The observed cross section is extrapolated to the full kinematic region in pT(D*±) and η(D*±) in order to determine the charm contribution, Fcc̄2 (x, Q2), to the proton structure function. The ratio Fcc̄2/F2 rises from ≃10% at Q2 ≃ 1.8GeV2 to ≃30% at Q2 ≃130GeV2 for x values in the range 10-4 to 10-3.

Quantitative Analysis Of Ultra-Fine Goethite In Rust Layer On Steel Using Mossbauer And X-Ray Diffraction Spectroscopy, Masato Yamashita, Toshihei Misawa, H. E. Townsend, D. C. Cook

Physics Faculty Publications

We have proposed determination procedure of the relative amounts of rust constituents of steel. Mossbauer spectroscopy provides the relative amounts of crystalline rust constituents including ultra-fine crystals. A quantitative analysis of ultra-fine crystals is possible with the resolution of several percent by comparing the Mossbauer results with the relative amounts of rust constituents determined by X-ray diffraction spectroscopy.

Renormalons As Dilation Modes In The Functional Space, A. Babansky, I. Balitsky

Physics Faculty Publications

There are two possible sources of the factorial large-order behavior of a typical perturbative series. First, the number of different Feynman diagrams may be large; second, there may be abnormally large diagrams known as renormalons. It is well known that the large combinatorial number of diagrams is described by instanton-type solutions of the classical equations. We demonstrate that, from the functional-integral viewpoint, the renormalons do not correspond to a particular configuration but manifest themselves as dilatation modes in the functional space.

High Energy Effective Action From Scattering Of Shock Waves In Qcd, Ian Balitsky

Physics Faculty Publications

The author demonstrates that the amplitude for high-energy scattering can be factorized as a convolution of the contributions due to fast and slow fields. The fast and slow fields interact by means of Wilson-line operators -- infinite gauge factors ordered along the straight line. The resulting factorization formula gives a starting point for a new approach to the effective action for high-energy scattering in QCD.

Mirroring And Mimicking Of Partial Cross Sections In The Vicinity Of A Resonance, Chien-Nan Liu, Anthony F. Starace

Anthony F. Starace Publications

We review recent analytical work on mirroring and mimicking behavior of resonance profiles in different partial cross sections. This work is related to the work of Fano and Cooper on resonance profiles in total cross sections and that of Starace on resonance profiles in partial cross sections. Applications of the new theories (describing mirroring and mimicking behavior) to recent experimental measurements and theoretical predictions for photoionization, photodetachment, and Auger spectroscopy in the vicinity of resonance structures are discussed.

Interaction Of Laser Radiation With A Negative Ion In The Presence Of A Strong Static Electric Field, N. L. Manakov, M. V. Frolov, Anthony F. Starace, Ilya I. Fabrikant

Anthony F. Starace Publications

This paper provides a general theoretical description of a weakly bound atomic system (a negative ion) interacting simultaneously with two (generally strong) fields, a static electric field and a monochromatic laser field having an arbitrary elliptical polarization. The zero-range δ-potential is used to model the interaction of a bound electron in a negative ion as well as the interaction of a detached electron with the residual atom. Our treatment combines the quasistationary (complex energy) and quasienergy (Floquet) approaches. This quasistationary, quasienergy state (QQES) formalism is the most appropriate one for analysing a decaying quantum system under the influence of a …

Neutron Scattering From Aerosols: Intraparticle Structure Factor, Guinier Analysis Of Particle Speed, And Crossed Beam Kinematics, Gerald Wilemski

Physics Faculty Research & Creative Works

A theoretical formalism for neutron scattering from systems of particles is applied to liquid nanodroplet aerosols. A term arising from intraparticle, intermolecular correlations is identified. The kinematical theory of two body scattering is recast into a form convenient for interpreting the results of experiments with crossed beams of neutrons and aerosol particles. Based on a theoretical analysis of the scattered intensity in the Guinier region, a method for determining the particle velocity directly from the experimental data is outlined. The method is not restricted by assumptions about particle shape, composition, uniformity, or size distribution.

Applications Of The Atomic Force Microscope Within The Fields Of Haematology And Cytogenetics, Margaret O'Reilly-Crowley

Theses

Atomic force microscopy [AFM] has become a rapidly developing interdisciplinary field of research in recent years. The technique, including instrumentation and specimen preparation methods, is now more sophisticated and its application has increased dramatically. The key advantage of AFM is in providing three-dimensional images of samples imaged. Both size and shape of samples imaged can be obtained allowing their subsequent quantification. Red blood cells [RBCs] and chromosomes were imaged in this work. A brief overview of the current status of biomedical AFM, has been presented in the review.

Measurement of mean cell volume [MCV] of immobilised red blood cells with …

Optical Performance Of Grazing Incidence X-Ray / Euv Telescopes For Space Science Applications, Patrick Louis Thompson

Retrospective Theses and Dissertations

The science and technology of X-rays has only been part of human achievement for the past 100 years, while the study of image formation in general has endured for as long as 1000 years. The ability to conceive, design, and fabricate X-ray imagers, moreover, has existed for only the past 70 years, and X-ray astronomical telescopes have been in use for a mere 35 years. Considering that aplanatic, normal incidence telescope designs required more than 400 years to perfect, it is most interesting to note that the development of ‘aplanatic’ grazing incidence telescopes has taken only about 40 years. In …

Group Invariant Solutions Without Transversality, Ian M. Anderson, Mark E. Fels, Charles G. Torre

All Physics Faculty Publications

We present a generalization of Lie's method for finding the group invariant solutions to a system of partial differential equations. Our generalization relaxes the standard transversality assumption and encompasses the common situation where the reduced differential equations for the group invariant solutions involve both fewer dependent and independent variables. The theoretical basis for our method is provided by a general existence theorem for the invariant sections, both local and global, of a bundle on which a finite dimensional Lie group acts. A simple and natural extension of our characterization of invariant sections leads to an intrinsic characterization of the reduced …

Modeling The Evolution Of Meso-Scale Ionospheric Irregularities At High Latitudes, Jan Josef Sojka, L. Zhu, M. David, Robert W. Schunk

All Physics Faculty Publications

The modeling of ionospheric plasma density irregularities (ΔN/N) is a necessary first step towards forecasting ionospheric scintillation effects. This modeling challenge is difficult not only because the linear‐nonlinear saturation levels of instabilities are not completely understood but also because ΔN/N often evolves on time scales which are long compared to the characteristic time constants of the instability drivers. In this study, the linear 1‐D gradient drift instability (GDI) is used in a high latitude simulation of ΔN/N evolution. For the first time snapshots (maps) of ΔN/N are presented demonstrating that it is possible to use …

Model Study Of Ionospheric Dynamics During A Substorm, Lie Zhu, Robert W. Schunk, Jan Josef Sojka, Michael David

All Physics Faculty Publications

A global substorm electrodynamic model and a global ionospheric model were coupled in order to study ionospheric dynamics during substorms, with the focus on small-scale substorm electrodynamic and plasma structures. The simulation results show that in the expansion phase, structured precipitation and channeled field-aligned currents quickly develop in the substorm onset region. The Hall and Pedersen conductance ratio in the region increases significantly, and the magnetospheric field-aligned currents are mainly closed by highly structured Hall currents. Correspondingly, the plasma in the ionosphere also undergoes significant changes during a substorm and is highly structured in both the horizontal and vertical directions. …

Sensitivity Curves For Spaceborne Gravitational Wave Interferometers, Shane L. Larson, William A. Hiscock, Ronald W. Hellings

All Physics Faculty Publications

To determine whether particular sources of gravitational radiation will be detectable by a specific gravitational wave detector, it is necessary to know the sensitivity limits of the instrument. These instrumental sensitivities are often depicted (after averaging over source position and polarization) by graphing the minimal values of the gravitational wave amplitude detectable by the instrument versus the frequency of the gravitational wave. This paper describes in detail how to compute such a sensitivity curve given a set of specifications for a spaceborne laser interferometer gravitational wave observatory. Minor errors in the prior literature are corrected, and the first (mostly) analytic …

Using Binary Star Observations To Bound The Mass Of The Graviton, Shane L. Larson, William A. Hiscock

All Physics Faculty Publications

Interacting white dwarf binary star systems, including helium cataclysmic variable (HeCV) systems, are expected to be strong sources of gravitational radiation, and should be detectable by proposed space-based laser interferometer gravitational wave observatories such as LISA. Several HeCV star systems are presently known and can be studied optically, which will allow electromagnetic and gravitational wave observations to be correlated. Comparisons of the phases of a gravitational wave signal and the orbital light curve from an interacting binary white dwarf star system can be used to bound the mass of the graviton. Observations of typical HeCV systems by LISA could potentially …

Extended Conformal Symmetry, James Thomas Wheeler

All Physics Faculty Publications

We show that the grading of fields by conformal weight, when built into the initial group symmetry, provides a discrete, non-central conformal extension of any group containing dilatations. We find a faithful vector representation of the extended conformal group and show that it has a scale-invariant scalar product and satisfies a closed commutator algebra. The commutator algebra contains the infinite Heisenberg and Virasoro algebras. In contrast to the classical treatment of scale invariance, covariant derivatives and gauge transformations automatically incorporate the correct conformal weights when the extended symmetry is gauged.

Actions For Biconformal Matter, Andre Wehner, James Thomas Wheeler

All Physics Faculty Publications

We extend 2n-dim biconformal gauge theory by including Lorentz-scalar matter fields of arbitrary conformal weight. For a massless scalar field of conformal weight zero in a torsion-free biconformal geometry, the solution is determined by the Einstein equation on an n-dim submanifold, with the stress-energy tensor of the scalar field as source. The matter field satisfies the n-dim Klein-Gordon equation.

Measurement Of Silicon Surface Recombination Velocity Using Ultrafast Pump-Probe Reflectivityin The Near Infrared, A. J. Sabbah, D. Mark Riffe

All Physics Faculty Publications

We demonstrate that ultrafast pump–probe reflectivity measurements from bulk Si samples using a Ti:sapphire femtosecond oscillator (λ=800 nm) can be used to measure the Si surface recombination velocity. The technique is sensitive to recombination velocities greater than ∼10⁴ cm s⁻¹

Inception Of Snapover And Gas Induced Glow Discharges, J. T. Galofaro, B. V. Vayner, D. C. Ferguson, W. A. Degroot, C. D. Thomson, John R. Dennison, R. E. Davies

All Physics Faculty Publications

Ground based experiments of the snapover phenomenon were conducted in the large vertical simulation chamber at the Glenn Research Center (GRC) Plasma Interaction Facility (PIF). Two Penning sources provided both argon and xenon plasmas for the experiments. The sources were used to simulate a variety of ionospheric densities pertaining to a spacecraft in a Low Earth Orbital (LEO) environment. Secondary electron emission is believed responsible for dielectric surface charging, and all subsequent snapover phenomena observed. Voltage sweeps of conductor potentials versus collected current were recorded in order to examine the specific charging history of each sample. The average time constant …