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Articles 11581 - 11610 of 14643

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Coulomb Sum Rule For ⁴He, J. Carlson, J. Jourdan, R. Schiavilla, I. Sick Jan 2003

Coulomb Sum Rule For ⁴He, J. Carlson, J. Jourdan, R. Schiavilla, I. Sick

Physics Faculty Publications

We determine the Coulomb sum for ⁴He using the world data on ⁴He(e,e′) and compare the results to calculations based on realistic interactions and including two-body components in the nuclear charge operator. We find good agreement between theory and experiment when using free-nucleon form factors. The apparent reduction of the in-medium GEp implied by IA-interpretation of the L/T-ratios measured in ⁴He(e,e′p) and ⁴He(e→,e′p→) is not confirmed.

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Coulomb Sum Rule For 4He, J. Carlson, J. Jourdan, Rocco Schiavilla, I. Sick Jan 2003

Coulomb Sum Rule For 4He, J. Carlson, J. Jourdan, Rocco Schiavilla, I. Sick

Physics Faculty Publications

We determine the Coulomb sum for 4He using the world data on 4He(e,e′) and compare the results to calculations based on realistic interactions and including two-body components in the nuclear charge operator. We find good agreement between theory and experiment when using free-nucleon form factors. The apparent reduction of the in-medium GEp implied by IA-interpretation of the L/T-ratios measured in 4He(e,e′p) and 4He(e→,e′p→) is not confirmed.

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Precision Measurement Of The Proton And Deuteron Spin Structure Functions G2 And Asymmetries A2, P. L. Anthony, R. G. Arnold, T. Averett, H. R. Band, N. Benmouna, W. Boeglin, H. Borel, P. E. Bosted, S. L. Bültmann, G. R. Court, C. E. Hyde-Wright, S. E. Kuhn, F. Sabatie, F. R. Wesselmann Jan 2003

Precision Measurement Of The Proton And Deuteron Spin Structure Functions G2 And Asymmetries A2, P. L. Anthony, R. G. Arnold, T. Averett, H. R. Band, N. Benmouna, W. Boeglin, H. Borel, P. E. Bosted, S. L. Bültmann, G. R. Court, C. E. Hyde-Wright, S. E. Kuhn, F. Sabatie, F. R. Wesselmann

Physics Faculty Publications

We have measured the spin struction functions g2(p) and g(2)(d) and the virtual photon asymmetries A(2)(p) and A(2)(d) over the kinetmatic range 0.02 less than or equal to x less than or equal to 0.8 and 0.7 less than or equal to Q2 less than or equal to 20 GeV2 by scattering 29.1 and 32.3 GeV longitudinally polarized electrons from transversely polarized NH3 and (LiD)-Li-6 targets. Our measured g2 approximately follows the twist-2 Wandzura-Wilczek calculation. The twist-3 reduced matrix elements d(2)(p) and d(2)(n) are less than two standard deviations from zero. The data are inconsistent with the Burkhardt-Cottingham …

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Kinematically Complete Measurement Of The Proton Structure Function F₂ In The Resonance Region And Evaluation Of Its Moments, M. Bektasoglu, L. Ciciani, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, A. V. Klimenko, S. E. Kuhn, F. Sabatié, S. Stepanyan, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration Jan 2003

Kinematically Complete Measurement Of The Proton Structure Function F₂ In The Resonance Region And Evaluation Of Its Moments, M. Bektasoglu, L. Ciciani, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, A. V. Klimenko, S. E. Kuhn, F. Sabatié, S. Stepanyan, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

We measured the inclusive electron-proton cross section in the nucleon resonance region (W <2.5 GeV) at momentum transfers Q2 below 4.5 (GeV/c)2 with the CLAS detector. The large acceptance of CLAS allowed the measurement of the cross section in a large, contiguous two-dimensional range of Q2 and x, making it possible to perform an integration of the data at fixed Q2 over the significant x interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q2 evolution of its moments, Mn(Q2), in order to estimate higher twist …

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Measurement Of Ep → E ' P Π⁺Π⁻ And Baryon Resonance Analysis, M. Bektasoglu, L. Ciciani, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, A. Klein, A. V. Klimenko, S. E. Kuhn, R. A. Niyazov, L. M. Qin, F. Sabatié, S. Stepanyan, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration Jan 2003

Measurement Of Ep → E ' P Π⁺Π⁻ And Baryon Resonance Analysis, M. Bektasoglu, L. Ciciani, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, A. Klein, A. V. Klimenko, S. E. Kuhn, R. A. Niyazov, L. M. Qin, F. Sabatié, S. Stepanyan, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

The cross section for the reaction ep→ e'pπ+π- was measured in the resonance region for 1.4 2 < 1.5 GeV2/c2using the CLAS detector at Jefferson Laboratory. The data show resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on N* and Δ states shows an evident discrepancy. A better description of the data is obtained either by a sizable change of the properties of the P13(1720) resonance or by introducing a new baryon state, not reported in published analyses.

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Phase Transitions Occurring In Models Of Neighborhood Racial Segregation, Alexander J. Laurie '03 Jan 2003

Phase Transitions Occurring In Models Of Neighborhood Racial Segregation, Alexander J. Laurie '03

Honors Projects

This thesis is organized as two chapters whose contents are closely related yet quite distinct. The first chapter presents a paper "Role of 'Vision' in Neighborhood Racial Segregation: A Variant of the Schelling Segregation Model," authored by myself and Dr. Jaggi, which has been accepted for publication by the journal Urban Studies and is currently in press (as of April 2003). This chapter introduces the well-known Schelling model of neighborhood segregation, outlines the sociopolitical motivation for our work, and presents the key results that we believe are of interest to social scientists. Chapter two, which ought to be of greater …

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High Precision Wavelength Measurements Of Qed-Sensitive Forbidden Transitions In Highly Charged Argon Ions, I. Draganić, J. R. Crespo López-Urrutia, Robert D. Dubois, S. Fritzsche, V. M. Shabaev, R. Soria Orts, I. I. Tupitsyn, Y. Zou, J. Ullrich Jan 2003

High Precision Wavelength Measurements Of Qed-Sensitive Forbidden Transitions In Highly Charged Argon Ions, I. Draganić, J. R. Crespo López-Urrutia, Robert D. Dubois, S. Fritzsche, V. M. Shabaev, R. Soria Orts, I. I. Tupitsyn, Y. Zou, J. Ullrich

Physics Faculty Research & Creative Works

We present the results of an experimental study of magnetic dipole ([Formula presented]) transitions in highly charged argon ions (ArX, ArXI, ArXIV, ArXV) in the visible spectral range using an electron beam ion trap. their wavelengths were determined with, for highly charged ions, unprecedented accuracy up to the sub-ppm level and compared with theoretical calculations. the QED contributions, calculated in this Letter, are found to be 4 orders of magnitude larger than the experimental error and are absolutely indispensable to bring theory and experiment to a good agreement. This method shows great potential for the study of QED effects in …

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Perturbative And Nonperturbative Calculations Of Electron-Hydrogen Ionization, Stephenie J. Jones, Don H. Madison, Mark D. Baertschy Jan 2003

Perturbative And Nonperturbative Calculations Of Electron-Hydrogen Ionization, Stephenie J. Jones, Don H. Madison, Mark D. Baertschy

Physics Faculty Research & Creative Works

We compare calculations of the fully differential cross section for ionization of atomic hydrogen by electron impact using two different theories-the perturbative CDW-EIS (continuum distorted wave with eikonal initial state) approximation and the nonperturbative ECS (exterior complex scaling) method. For this comparison, we chose an impact energy of 54.4 eV, since this is near the lowest energy that our perturbative approach would be applicable and near the highest energy that can be tackled by the ECS method with our present computational resources. For the case of equal-energy outgoing electrons investigated here, the two theories predict nearly identical results except that …

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Electron Loss From 0.74- And 1.4-Mev/U Low-Charge-State Argon And Xenon Ions Colliding With Neon, Nitrogen, And Argon, Robert D. Dubois, Antonio C. Santos, Ronald E. Olson, Th Stöhlker, F. Bosch, A. Bräuning-Demian, A. Gumberidze, S. Hagmann, C. Kozhuharov, R. Mann, A. Oršić Muthig, U. Spillmann, S. Tachenov, W. Barth, L. Dahl Jan 2003

Electron Loss From 0.74- And 1.4-Mev/U Low-Charge-State Argon And Xenon Ions Colliding With Neon, Nitrogen, And Argon, Robert D. Dubois, Antonio C. Santos, Ronald E. Olson, Th Stöhlker, F. Bosch, A. Bräuning-Demian, A. Gumberidze, S. Hagmann, C. Kozhuharov, R. Mann, A. Oršić Muthig, U. Spillmann, S. Tachenov, W. Barth, L. Dahl

Physics Faculty Research & Creative Works

Absolute total-, single-, and multiple-electron-loss cross sections are measured for (Ar+-, Ar2+-, Xe3+)-~Ne, N2 Ar) collisions at 0.74 and 1.4 MeV/u. in addition, a many-body classical trajectory Monte Carlo model was used to calculate total- and multiple-electron-loss cross sections for Ar+ impact. for N2 and Ar targets, excellent agreement between the measured and calculated cross sections is found; for the Ne target the experimental data are approximately 40% smaller than the theoretical predictions. the experimental data are also used to examine cross-section scaling characteristics for electron loss from fast, low-charge-state, heavy …

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Target Z Dependence And Additivity Of Cross Sections For Electron Loss By 6-Mev/Amu [Formula Presented] Projectiles, R. L. Watson, Yong Peng, V. Horvat, G. J. Kim, Ronald E. Olson Jan 2003

Target Z Dependence And Additivity Of Cross Sections For Electron Loss By 6-Mev/Amu [Formula Presented] Projectiles, R. L. Watson, Yong Peng, V. Horvat, G. J. Kim, Ronald E. Olson

Physics Faculty Research & Creative Works

The dependence of electron loss by 6-MeV/amu Xe18+ on target atomic number was investigated by measuring single-collision cross sections for loss of one to eight electrons in targets of the noble gases He, Ne, Ar, Kr, and Xe. the total-electron-loss cross sections were found to increase linearly with target atomic number, but an abrupt slope change was observed to occur between Ne and Kr. Calculated total-loss cross sections obtained using the n-body classical trajectory Monte Carlo method were in good agreement with the measurements. the dependence of the individual cross sections on the number of electrons lost was reasonably …

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Aspects Of Conformal Field Theory From Calabi-Yau Arithmetic, Rolf Schimmrigk Jan 2003

Aspects Of Conformal Field Theory From Calabi-Yau Arithmetic, Rolf Schimmrigk

Faculty Articles

This paper describes a framework in which techniques from arithmetic algebraic geometry are used to formulate a direct and intrinsic link between the geometry of Calabi-Yau manifolds and aspects of the underlying conformal field theory. As an application the algebraic number field determined by the fusion rules of the conformal field theory is derived from the number theoretic structure of the cohomological Hasse-Weil L-function determined by Artin's congruent zeta function of the algebraic variety. In this context a natural number theoretic characterization arises for the quantum dimensions in this geometrically determined algebraic number field.

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Multiphoton Detachment Of A Negative Ion By An Elliptically Polarized, Monochromatic Laser Field, N. L. Manakov, M. V. Frolov, Bogdan Borca, Anthony F. Starace Jan 2003

Multiphoton Detachment Of A Negative Ion By An Elliptically Polarized, Monochromatic Laser Field, N. L. Manakov, M. V. Frolov, Bogdan Borca, Anthony F. Starace

Anthony F. Starace Publications

The quasistationary quasienergy state approach (QQES) is applied to the analysis of partial (n-photon) decay rates and angular distributions (ADs) of photoelectrons produced by an elliptically polarized laser field. The problem is formulated for a weakly bound electron with an energy E0 in the three-dimensional δ-model potential (which approximates the short-range potential of a negative ion) interacting with a strong monochromatic laser field having an electric vector F(ωt).The results presented cover weak (perturbative), strong (nonperturbative), and superstrong field regimes as well as a wide interval of frequencies ω extending from the tunnelling (ħω << |E0 …

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Molecular Dynamics Simulation Of The Order-Disorder Phase Transition In Solid Nano2, Wei-Guo Yin, Chun-Gang Duan, Wai-Ning Mei, Jianjun Liu, R. W. Smith, John R. Hardy Jan 2003

Molecular Dynamics Simulation Of The Order-Disorder Phase Transition In Solid Nano2, Wei-Guo Yin, Chun-Gang Duan, Wai-Ning Mei, Jianjun Liu, R. W. Smith, John R. Hardy

John R. Hardy Papers

We present molecular dynamics simulations of solid NaNO2 using pair potentials with the rigid-ion model. The crystal potential surface is calculated by using an a priori method which integrates the ab initio calculations with the Gordon-Kim electron gas theory. This approach is carefully examined by using different population analysis methods and comparing the intermolecular interactions resulting from this approach with those from the ab initio Hartree-Fock calculations. Our numerics show that the ferroelectric-paraelectric phase transition in solid NaNO2 is triggered by rotation of the nitrite ions around the crystallographical c axis, in agreement with recent x-ray experiments [Gohda …

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Spin-Dependent Tunneling In Magnetic Tunnel Junctions, Evgeny Y. Tsymbal, O. N. Mryasov, Patrick R. Leclair Jan 2003

Spin-Dependent Tunneling In Magnetic Tunnel Junctions, Evgeny Y. Tsymbal, O. N. Mryasov, Patrick R. Leclair

Evgeny Tsymbal Publications

The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunneling in magnetic tunnel junctions (MTJs) has recently aroused enormous interest and has developed in a vigorous field of research. The large tunneling magnetoresistance (TMR) observed in MTJs garnered much attention due to possible applications in non-volatile random access memories and next-generation magnetic field sensors. This led to a number of fundamental questions regarding the phenomenon of spindependent tunneling. In this review article we present an …

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Light Storage With Light Of Arbitrary Polarization, Hong Gao, Mark Rosenberry, Herman Batelaan Jan 2003

Light Storage With Light Of Arbitrary Polarization, Hong Gao, Mark Rosenberry, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

We have demonstrated the phase coherence of stored light in Rb vapor with a completely optical technique. Combining this technique with polarization measurements provides strong evidence that arbitrary polarizations can be stored. The fidelity obtained exceeds 95% for all polarizations. We view the capability to store polarizations as a first step towards building a quantum memory in such a system.

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Electron Bernstein Wave-X-O Mode Conversion And Electron Cyclotron Emission In Mast, Josef Preinhaelter, Pavol Pavlo, Vladimir Shevchenko, Martin Valovic, Linda L. Vahala, George Vahala Jan 2003

Electron Bernstein Wave-X-O Mode Conversion And Electron Cyclotron Emission In Mast, Josef Preinhaelter, Pavol Pavlo, Vladimir Shevchenko, Martin Valovic, Linda L. Vahala, George Vahala

Electrical & Computer Engineering Faculty Publications

Electron cyclotron emission (ECE) from overdense plasmas can only occur due to electron Bernstein waves (EBW) mode converting near the upper hybrid region to an electromagnetic wave. Experimental data of ECE observations on MAST are studied and compared with EBW-X-O mode conversion modeling results.

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Modeling Of Infrared Radiation For All Skies From Easy-To-Measure Meteorological Parameters At Tropical Location: Ilorin, Nigeria, Sunday O. Udo Jan 2003

Modeling Of Infrared Radiation For All Skies From Easy-To-Measure Meteorological Parameters At Tropical Location: Ilorin, Nigeria, Sunday O. Udo

Turkish Journal of Physics

Downward infrared radiation (L) and some easy-to-measure meteorological variables (relative humidity, clearness index and vapour pressure) were collected for a period of two years at Ilorin. Downward infrared radiation data were obtained using a pyrgeometer (Eppley-PIR), while data for relative humidity and vapour pressure for Ilorin were obtained from the Nigerian Meteorological Services, Lagos. Based on these data, using statistical regression analysis, empirical models (seven one-variable and nine two-variable) for predicting daily mean infrared radiation, from both clear and cloudy skies, were tested. Their advantage is that they only make use of easily measured meteorological parameters. The best one-variable model …

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Interaction Integrals Of Extended Bodies And Convolution/Folding Operation, Şule Kehnemi̇, R. Ömür Akyüz Jan 2003

Interaction Integrals Of Extended Bodies And Convolution/Folding Operation, Şule Kehnemi̇, R. Ömür Akyüz

Turkish Journal of Physics

The convolution, or folding, theorem related to Fourier transforms is applied to the evaluation of interaction integrals of certain extended bodies for the specific purpose of nuclear applications The integrals give analytical results for a class of functions when chosen from among uniform sharp and leptodermous spheres, delta-points, Yukawa, and Coulomb shapes. Such shapes are convenient to use as models for source density and point-point interaction.

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Adiabatic Quantum Pumping Of Coherent Electrons, Ora Entin-Wohlman, Amnon Aharony, Vyacheslavs Kashcheyevs Jan 2003

Adiabatic Quantum Pumping Of Coherent Electrons, Ora Entin-Wohlman, Amnon Aharony, Vyacheslavs Kashcheyevs

Turkish Journal of Physics

We review recent theoretical calculations of charge transfer through mesoscopic devices in response to slowly-oscillating, spatially-confined, potentials. The discussion is restricted to non-interacting electrons, and emphasizes the role of quantum interference and resonant transmission in producing almost integer values (in units of the electronic charge e) of the charge transmitted per cycle, Q. The expression for the pumped charge is derived from a systematic expansion of the system scattering states in terms of the temporal derivatives of the instantaneous solutions. This yields the effect of the modulating potential on the Landauer formula for the conductance in response to a constant …

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Persistent Currents In Mesoscopic Loops And Networks, Igor O. Kulik Jan 2003

Persistent Currents In Mesoscopic Loops And Networks, Igor O. Kulik

Turkish Journal of Physics

The paper describes persistent (also termed ``permanent", or ``non-decaying") currents in mesoscopic metallic and macromolecular rings, cylinders and networks. The current arises as a response of system to Aharonov-Bohm flux threading the conducting loop and does not require external voltage to support the current. Magnitude of the current is periodic function of magnetic flux with a period of normal-metal flux quantum \Phi_0 = hc/e. Spontaneous persistent currents arise in regular macromolecular structure without the Aharonov-Bohm flux provided the azimuthal periodicity of the ring is insured by strong coupling to periodic background (a ``substrate"), otherwise the system will undergo the Peierls …

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Mean Multiplicity Of Quark And Gluon Jets As A Function Of Opening Angle In E^{+}E^{-} \Rightarrow B\Overline{B} G Events, Ayda Beddall Jan 2003

Mean Multiplicity Of Quark And Gluon Jets As A Function Of Opening Angle In E^{+}E^{-} \Rightarrow B\Overline{B} G Events, Ayda Beddall

Turkish Journal of Physics

A comparison of the properties of quark and gluon jets has been madeby Monte Carlo simulation of the reaction Z \rightarrow b \overline{b} g. The jet energy is held fixed for every 5 GeV between 15--30 GeV energies and the mean multiplicity of b-quark and gluon jets are obtained as function of the angle between them. It is seen that the jet properties not only depend on the jet energies but also on the angle between the jets.

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Physical Properties Of Spray Pyrolysed Cds Thin Films, A. Ashour Jan 2003

Physical Properties Of Spray Pyrolysed Cds Thin Films, A. Ashour

Turkish Journal of Physics

Cadmium sulphide (CdS) thin films were prepared by chemical spray-pyrolysis technique. Cleaned glass substrates were used. The substrate temperature was varied in the range 200 -- 400 °C and seems to be one of the more important parameters affecting the physical properties of the semiconductor. The films were characterized by X-ray diffraction (XRD). XRD patterns indicated the presence of single-phase hexagonal CdS. The resistivity of the as-deposited films was found to vary in the range 10^3 - 10^5 \Omega. Cm, depending on the substrate temperature. Direct band gap values of 2.39--2.42 eV were obtained from optical absorption measurements.

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Measurement Of Proton-Dissociative Diffractive Photoproduction Of Vector Mesons At Large Momentum Transfer At Hera: The Zeus Collaboration, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan, D. Bartsch Jan 2003

Measurement Of Proton-Dissociative Diffractive Photoproduction Of Vector Mesons At Large Momentum Transfer At Hera: The Zeus Collaboration, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan, D. Bartsch

Faculty Publications

Diffractive photoproduction of vector mesons, γp → VY, where Y is a proton-dissociative system, has been measured in e+p interactions with the ZEUS detector at HERA using an integrated luminosity of 25 pb-1. The differential cross section, dσ/dt, is presented for 1.2 < -t < 12 GeV2, where t is the square of the four-momentum transferred to the vector meson. The data span the range in photon-proton centre-of-mass energy, W, from 80 GeV to 120 GeV. The t distributions are well fit by a power law, dσ/dt ∝ (-t)-n. The slope of the effective Pomeron trajectory, measured from the W dependence of the ρ0 and φ cross sections in bins of t, is consistent with zero. The ratios dσγp→φY/dt to dσγp→ρ0Y/dt and dσγp→J/ψY/dt to dσγp→ρ0Y/dt increase with increasing -t. Decay-angle analyses for ρ0, φ and J/ψ mesons have been carried out. For the ρ0 and φ mesons, contributions from single and double helicity flip are observed. The results are compared to expectations of theoretical models.

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Viscoelasticity From A Microscopic Model Of Dislocation Dynamics, M. Christina Marchetti, Karl Saunders Dec 2002

Viscoelasticity From A Microscopic Model Of Dislocation Dynamics, M. Christina Marchetti, Karl Saunders

Physics

It is shown that the dynamics of a viscoelastic medium can be modeled as that of a two-dimensional crystal with a finite concentration of dislocations, as well as vacancy and interstitial defects. At the longest length scales the viscoelasticity is described by the simplest Maxwell model, whose shear and compressional relaxation times are obtained in terms of microscopic quantities, including the density of free dislocations. At short length scales, t bond orientational order effects become important and lead to wave vector dependent corrections to the relaxation times.

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Search For Radiative B,-Hadron Decays In Pp̅ Collisions At √S=1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 2002

Search For Radiative B,-Hadron Decays In Pp̅ Collisions At √S=1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have performed a search for radiative b-hadron decays using events produced in pp̅ collisions at √s=1.8 TeV and collected by the Collider Detector at Fermilab. The decays we considered were B̅d0→K*0(→K-π+) γ, B̅s0→φ(→K+K-) γ, Λb0→ Λ(→pπ-) γ, and their charge conjugates. Two independent methods to identify photons from such decays were employed. In the first method, the photon was detected in the electromagnetic calorimeter. In the second method, the photon was identified …

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Limits On Extra Dimensions And New Particle Production In The Exclusive Photon, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 2002

Limits On Extra Dimensions And New Particle Production In The Exclusive Photon, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

The exclusive γE/T signal has a small standard model cross section and is thus a channel sensitive to new physics. This signature is predicted by models with a superlight gravitino or with large extra spatial dimensions. We search for such signals at the Collider Detector at Fermilab, using 87   pb-1 of data at √s=1.8   TeV, and extract 95% C.L. limits on these processes. A limit of 221 GeV is set on the scale |F|1/2 in supersymmetric models. For 4, 6, and 8 extra dimensions, model-dependent limits on the fundamental mass scale MD of 0.55, 0.58, and …

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Perturbative Calculation Of The Triply Differential Cross Section For Photo-Double-Ionization Of He, Andrei Y. Istomin, N. L. Manakov, Anthony F. Starace Dec 2002

Perturbative Calculation Of The Triply Differential Cross Section For Photo-Double-Ionization Of He, Andrei Y. Istomin, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

Single-photon, two-electron ionization of He is analyzed, taking into account electron correlation using lowest-order perturbation theory and including all individual electron angular momenta in the final two-electron continuum. Perturbative account of electron correlation in the final state, which describes the so-called TS-1 mechanism of double photoionization, combined with a variational account of electron screening, is found to provide results for the triply differential cross section at an excess energy of 20 eV that are in excellent agreement with both absolute experimental data and results of non-perturbative calculations, for all kinematics of the process in which the TS-1 mechanism is expected …

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Chaotic Free-Space Laser Communication Over Turbulent Channel, N. F. Rulkov, Mikhail Vorontsov, L. Illing Dec 2002

Chaotic Free-Space Laser Communication Over Turbulent Channel, N. F. Rulkov, Mikhail Vorontsov, L. Illing

Electro-Optics and Photonics Faculty Publications

The dynamics of errors caused by atmospheric turbulence in a self-synchronizing chaos-based communication system that stably transmits information over a ∼5  km free-space laser link is studied experimentally. Binary information is transmitted using a chaotic sequence of short-term pulses as a carrier. The information signal slightly shifts the chaotic time position of each pulse depending on the information bit. We report the results of an experimental analysis of the atmospheric turbulence in the channel and the impact of turbulence on the bit-error-rate performance of this chaos-based communication system.

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He Ii Reverberation In Active Galactic Nucleus Spectra, Mark C. Bottorff, Jack A. Baldwin, Gary J. Ferland, Jason W. Ferguson, Kirk T. Korista Dec 2002

He Ii Reverberation In Active Galactic Nucleus Spectra, Mark C. Bottorff, Jack A. Baldwin, Gary J. Ferland, Jason W. Ferguson, Kirk T. Korista

Physics and Astronomy Faculty Publications

This paper compares the observed reverberation response lags and the intensity ratios of the broad-line region (BLR) emission lines He II λ1640, He II λ4686, and C IV λ1549 with predictions. Published observations indicate that the He II λ1640 lag is 3 times shorter than the lags of He II λ4686 or C IV λ1549. Diverse models, however, do not reproduce this observation. Extensive improved numerical simulations of the hydrogenic isoelectronic sequence emission show that the He II spectrum remains especially simple, even in the central regions of a luminous quasar. Line trapping never builds up a significant population of …

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Two-Photon Bremsstrahlung Processes In Atoms: Polarization Effects And Analytic Results For The Coulomb Potential, A. A. Krylovetskiĭ, N. L. Manakov, S. I. Marmo, Anthony F. Starace Dec 2002

Two-Photon Bremsstrahlung Processes In Atoms: Polarization Effects And Analytic Results For The Coulomb Potential, A. A. Krylovetskiĭ, N. L. Manakov, S. I. Marmo, Anthony F. Starace

Anthony F. Starace Publications

The partial wave analysis of two-photon free–free (bremsstrahlung) electron transition cross sections during scattering by a static potential U(r), as well as by an atom with a nonzero angular momentum, is carried out. The dipole interaction with radiation is taken into account in the second order of perturbation theory for the general case of elliptic polarization of photons. The polarization and angular dependences of the twophoton potential scattering amplitude is presented as a combination of the scalar product of electron momenta and photon polarization vectors and five atomic parameters containing Legendre polynomials of the scattering angle as …

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