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Laser-Controlled Local Magnetic Field With Semiconductor Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

We analyze theoretically the dynamics of N electrons localized in a narrow semiconductor quantum ring under a train of phase-locked infrared laser pulses. The pulse sequence is designed to control the total angular momentum of the electrons. The quantum ring can be put in states characterized by strong currents. The local magnetic field created by these currents can be used for a selective quantum control of single spins in semiconductor systems. The current generation in quantum rings with finite width is also studied.

Spin-Photovoltaic Effect In Quantum Wires Due To Intersubband Transitions, Arkady Fedorov, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

We consider the current induced in a quantum wire by external electromagnetic radiation. The photocurrent is caused by the interplay of spin-orbit interaction (Rashba and Dresselhaus terms) and an external in-plane magnetic field. We calculate this current using a Wigner functions approach, taking into account radiation-induced transitions between transverse subbands. The magnitude and the direction of the current depends on the Dresselhaus and Rashba constants, strength of magnetic field, radiation frequency, and intensity. The current can be controlled by changing some of these parameters.

Klein Paradox With Spin-Resolved Electrons And Positrons, P Krekora, Q Su, Rainer Grobe

Faculty publications – Physics

Using numerical solutions to relativistic quantum field theory with space-time resolution, we illustrate how an incoming electron wave packet with a definite spin scatters off a supercritical potential step. We show that the production rate is reduced of only those electrons that have the same spin as the incoming electron is reduced. This spin-resolved result further clarifies the importance of the Pauli-exclusion principle for the Klein paradox.

Phys 3003 Course Proposal 12/01/2005, Curriculum Committee

Curriculum Committee Reports

No abstract provided.

Low Magnetic Prandtl Number Dynamos With Helical Forcing, Pablo D. Mininni, David C. Montgomery

Dartmouth Scholarship

We present direct numerical simulations of dynamo action in a forced Roberts flow. The behavior of the dynamo is followed as the mechanical Reynolds number is increased, starting from the laminar case until a turbulent regime is reached. The critical magnetic Reynolds for dynamo action is found, and in the turbulent flow it is observed to be nearly independent on the magnetic Prandtl number in the range from ∼0.3 to ∼0.1. Also the dependence of this threshold with the amount of mechanical helicity in the flow is studied. For the different regimes found, the configuration of the magnetic and velocity …

Photovoltaic Effect In Bent Quantum Wires In The Ballistic Transport Regime, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

A scheme for the generation of a photocurrent in bent quantum wires is proposed. We calculate the current using a generalized Landauer-Büttiker approach that takes into account the electromagnetic radiation. For circularly polarized light, it is demonstrated that the curvature in the bent wire induces an asymmetry in the scattering coefficients for left and right moving electrons. This asymmetry results in a current at zero bias voltage. The effect is due to the geometry of the wire which transforms the photon angular momentum into translational motion for the electrons. Possible experimental realizations of this scheme are discussed.

Broadband Nulling Of A Vortex Phase Mask, Grover Jr Swartzlander

Articles

A pulse transmitted through a helical vortex phase mask undergoes a temporal Hilbert transform. The fluence transmitted into the unfavorable plane wave mode is found to increase as the square of the bandwidth and, to first order, is independent of the topological charge.

Limits Of Quintessence, R. R. Caldwell, Eric V. Linder

Dartmouth Scholarship

We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase plane of w and w′, the dark energy equation of state and its time derivative in units of the Hubble time. Restricting an energy scale of the dark energy microphysics limits how closely a scalar field can resemble a cosmological constant. These results, indicating a desired measurement resolution of order σ(w′)≈(1+w), …

Persistent And Radiation-Induced Currents In Distorted Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

Persistent and radiation-induced currents in distorted narrow quantum rings are theoretically investigated. We show that ring distorsions can be described using a geometrical potential term. We analyze the effect of this term on the current induced by a magnetic flux (persistent current) and by a polarized coherent electromagnetic field (radiation-induced current). The strongest effects in persistent currents are observed for distorted rings with a small number of electrons. The distortion smoothes the current oscillations as a function of the magnetic flux and changes the temperature dependence of the current amplitude. For radiation-induced currents, the distortion induces an ac component in …

Electron-Impact Ionization Of Hydrogen And Lithiumlike Systems, M A. Uddin, Abul Kalam Fazlul Haque, A K. Basak, Khondkar R. Karim, B C. Saha

Faculty publications – Physics

The electron impact single ionization cross sections on a number of targets with atomic number Z=1-92 in the H and Li isoelectronic sequences are calculated using a modified version of the recently propounded relativisitic improved binary-encounter dipole (MRIBED) model [M. A. Uddin , Phys. Rev. A 70, 032706 (2004); 71, 032715 (2005)]. The modified RQIBED (MRIBED) model along with a Z-dependent factor in it is found remarkably successful in the applications to H- and Li-like systems and also valid for the ionization of a filled s orbit including the He-like targets.

Investigation Of Laser Beam Induced Current Techniques For Heterojunction Photodiode Characterization, Weifu Fang, David A. Redfern, Kazufumi Ito, G. Bahir, Charles A. Musca, John M. Dell, Lorenzo Faraone

Mathematics and Statistics Faculty Publications

A reduced model is developed that has significant advantages over the full drift-diffusion model for the simulation of laser beam-induced current (LBIC) signals in the presence of heterojunctions. The model determines the contribution to the LBIC signal that would occur from photogeneration at any position within the semiconductor, and is particularly useful for heterostructures where judicious choice of illumination wavelength can result in photogeneration at different depths within the device structure. The reduced model is used to examine the basic features of LBIC as applied to two types of planar P-n HgCdTe heterojunction photodiode structures. In particular, the question of …

Simulation Of Charged Particle Trajectories In The Neutron Decay Correlation Experiment Abba, D. Desai, G. Greene, R. Mahurin, D. Bowman, John R. Calarco

Physics & Astronomy

The proposed neutron decay correlation experiment, abBA, will directly detect the direction of emission of decay protons and electrons as well as providing spectroscopic information for both particles. In order to provide this information, the abBA experiment incorporates spatially varying electric and magnetic fields. We report on detailed simulations of the decay particle trajectories in order to assess the impact of various systematic effects on the experimental observables. These include among others; adiabaticity of particle orbits, tracking of orbits, reversal of low energy protons due to inhomogeneous electric field, and accuracy of proton time of flight measurements. Several simulation methods …

Economics: The Next Physical Science?, J. Doyne Farmer, Martin Shubik, Eric Smith

Cowles Foundation Discussion Papers

We review an emerging body of work by physicists addressing questions of economic organization and function. We suggest that, beyond simply employing models familiar from physics to economic observables, remarkable regularities in economic data may suggest parts of social order that can usefully be incorporated into, and in turn can broaden, the conceptual structure of physics.

Temperature-Dependent Asymmetry Of The Nonlocal Spin-Injection Resistance: Evidence For Spin Nonconserving Interface Scattering, Samir Garzon, Igor Žutić, Richard A. Webb

Faculty Publications

We report nonlocal spin injection and detection experiments on mesoscopic Co-Al₂O₃-Cu spin valves. We have observed a temperature-dependent asymmetry in the nonlocal resistance between parallel and antiparallel configurations of the magnetic injector and detector. This strongly supports the existence of a nonequilibrium resistance that depends on the relative orientation of the detector magnetization and the nonequilibrium magnetization in the normal metal providing evidence for increasing interface spin scattering with temperature.

Cardiac Relaxation Dynamics Investigated By Doppler Tissue Imaging (Dti), Gerard J. King

Doctoral

Following an initial pilot study to explore the usefulness of Doppler tissue imaging (DTI) for the assessment of regional systolic dysfunction in the ischaemic heart, new techniques for the diagnosis of diastolic dysfunction have been developed

In the refinement of the techniques further evidence to support the existence of the early diastolic mechanism was obtained prior to assessing its clinical utility. For this the relationship between peak early diastolic mitral ring tissue velocity (EA) as a surrogate for recoil, and the acceleration of early transmitral flow (ventricular filling) was investigated in patients with diastolic dysfunction and in normal subjects. This …

Polarized He-3 Gas Compression System Using Metastability-Exchange Optical Pumping, D. S. Hussey, D. R. Rich, A. S. Belov, X. Tong, H. Yang, C. Bailey, C. D. Keith, J. Hartfield, G. D. R. Hall, T. C. Black, W. M. Snow, T. R. Gentile, W. C. Chen, Gordon L. Jones, Eileen Wildman '01

Articles

Dense samples (10-100 bar cm) of nuclear spin polarized He-3 are utilized in high energy physics, neutron scattering, atomic physics, and magnetic resonance imaging. Metastability exchange optical pumping can rapidly produce high He-3 polarizations (≈ 80%) at low pressures (few mbar). We describe a polarized He-3 gas compressor system which accepts 0.26 bar l h(-1) of He-3 gas polarized to 70% by a 4 W neodymium doped lanthanum magnesium hexaluminate (Nd:LMA) laser and compresses it into a 5 bar cm target with final polarization of 55%. The spin relaxation rates of the system's components have been measured using nuclear magnetic …

Microscopic Theory Of The Low Frequency Raman Modes In Germanium Nanocrystals, Shang-Fen Ren, Peter Y. Yu

Faculty publications – Physics

We have studied the Raman intensities of low-frequency phonon modes in germanium (Ge) nanocrystals (NC) with varying sizes by using a microscopic valence force field model. The results are compared with the predictions of the continuum model of Lamb using a projection method. We found that the l=0 spheroidal Lamb modes are Raman active in the parallel polarization scattering geometry, while the l=2 spheroidal Lamb modes are active in the crossed polarization geometry. This result agrees with the group theory prediction that the torsional Lamb modes are not Raman active, but is in disagreement with the identification of torsional Lamb …

Long-Lived Spin Coherence States In Semiconductor Heterostructures, Yuriy V. Pershin Dr

Faculty Publications

We study evolution of electron spin coherence having nonhomogeneous direction of spin polarization vector in semiconductor heterostructures. It is found that the electron spin relaxation time due to the D’yakonov- Perel’ relaxation mechanism essentially depends on the initial spin polarization distribution. This effect has its origin in the coherent spin precession of electrons diffusing in the same direction. We predict a long spin relaxation time of a novel structure: a spin coherence standing wave and discuss its experimental realization.

Computation Of Electron-Impact K-Shell Ionization Cross Sections Of Atoms, M A. Uddin, Abul Kalam Fazlul Haque, M Masum Billah, A K. Basak, Khondkar R. Karim, B C. Saha

Faculty publications – Physics

The total cross sections of electron impact single K-shell ionization of atomic targets, with a wide range of atomic numbers from Z=6-50, are evaluated in the energy range up to about 10 MeV employing the recently proposed modified version of the improved binary-encounter dipole (RQIBED) model [Uddin , Phys. Rev. A 70, 032706 (2004)], which incorporates the ionic and relativistic effects. The experimental cross sections for all targets are reproduced satisfactorily even in the relativistic energies using fixed generic values of the two parameters in the RQIBED model. The relativistic effect is found to be significant in all targets except …

High-Definition Vertically Aligned Liquid Crystal Microdisplays Using A Circularly Polarized Light, Kuan-Hsu Fan-Chiang, Shu-Hsia Chen, Shin-Tson Wu

Faculty Bibliography 2000s

A high-definition vertically aligned liquid crystal (LC) microdisplay exhibits a excellent contrast ratio, but its fringing field effect splits the bright state unevenly and leads to a very slow response time. By utilizing a circularly polarized light instead of conventional linearly polarized light, we have overcome the long-standing problems of poor sharpness, low brightness, and slow response time. Confirming computer simulations agree with the experimental results well. This approach can be applied to both reflective and transmissive LC microdisplays.

Against Realist Instruction: Superficial Success Masking Catastrophic Failure And An Alternative, Dewey I. Dykstra

Physics Faculty Publications and Presentations

Purpose: Often radical constructivists are confronted with arguments why radical constructivism is wrong. The present work presents a radical constructivist alternative to such arguments: a comparison of the results of two instructional practices, the standard, realistbased instruction and a radical constructivist-based instruction, both in physics courses. Design: Evidence from many studies of student conceptions in standard instruction (Duit 2004) is taken into account. In addition, diagnostic data, pre and post instruction, were collected from over 1,000 students in multiple institutions across the U. S. over a period of about 15 years via an established diagnostic of conceptual understanding of motion …

Mastering Physics?, Roger A. Lewis, Rodney Em Vickers, Carey A. Freeth

Faculty of Engineering - Papers (Archive)

MasteringPhysics is a tutorial software package. The University of Wollongong adopted it for one stream of first-year physics in second session 2004. The goal of the research is to determine the impact MasteringPhysics had on examination results in the subject and on student opinion of the subject.

A New Thz Facility For Condensed Matter Physics, R. A. Lewis, R.E.M. Vickers, M.L. Smith

Faculty of Engineering - Papers (Archive)

This paper describes a new THz facility for condensed matters physics that complements the existing infrastructure at the University of Wollongong (UOW).

Measurement Of B(T -> Wb)/B(T -> Wq) At The Collider Detector At Fermilab, D. Acosta, J. Adelman, T. Affolder, T. Akimoto, M. G. Albrow, D. Ambrose, S. Amerio, D. Amidei, A. Anastassov, K. Anikeev, A. Annovi, J. Antos, M. Aoki, G. Apollinari, T. Arisawa, J. F. Arguin, A. Artikov, W. Ashmanskas, A. Attal, F. Azfar, P. Azzi-Bacchetta, N. Bacchetta, H. Bachacou, W. Badgett, A. Barbaro-Galtieri, G. J. Barker, V. E. Barnes, B. A. Barnett, S. Baroiant, G. Bauer, F. Bedeschi, S. Behari, S. Belforte, G. Bellettini, J. Bellinger, A. Belloni, E. Ben-Haim, D. Benjamin, A. Beretvas, T. Berry, A. Bhatti, M. Binkley, D. Bisello, M. Bishai, R. E. Blair, C. Blocker, K. Bloom, B. Blumenfeld, A. Bocci, A. Bodek, G. Bolla, A. Bolshov, D. Bortoletto, J. Boudreau, S. Bourov, B. Brau, C. Bromberg, E. Brubaker, J. Budagov, H. S. Budd, K. Burkett, G. Busetto, P. Bussey, K. L. Byrum, S. Cabrera, M. Campanelli, M. Campbell, F. Canelli, A. Canepa, M. Casarsa, D. Carlsmith, R. Carosi, S. Carron, M. Cavalli-Sforza, A. Castro, P. Catastini, D. Cauz, A. Cerri, L. Cerrito, J. Chapman, Y. C. Chen, M. Chertok, G. Chiarelli, G. Chlachidze, F. Chlebana, I. Cho, K. Cho, D. Chokheli, J. P. Chou, S. Chuang, K. Chung, W. H. Chung, Y. S. Chung, M. Cijliak, C. I. Ciobanu, M. A. Ciocci, A. G. Clark, D. Clark, M. Coca, A. Connolly, M. Convery, J. Conway, B. Cooper, K. Copic, M. Cordelli, G. Cortiana, J. Cranshaw, J. Cuevas, A. Cruz, R. Culbertson, C. Currat, D. Cyr, D. Dagenhart, S. Da Ronco, S. D'Auria, P. De Barbaro, S. De Cecco, A. Deisher, G. De Lentdecker, M. Dell'orso, S. Demers, L. Demortier, M. Deninno, D. De Pedis, P. F. Derwent, C. Dionisi, J. R. Dittmann, P. Dituro, C. Dorr, A. Dominguez, S. Donati, M. Donega, J. Donini, M. D'Onofrio, T. Dorigo, K. Ebina, J. Efron, J. Ehlers, R. Erbacher, M. Erdmann, D. Errede, S. Errede, R. Eusebi, H. C. Fang, S. Farrington, I. Fedorko, W. T. Fedorko, R. G. Feild, M. Feindt, J. P. Fernandez, R. D. Field, G. Flanagan, L. R. Flores-Castillo, A. Foland, S. Forrester, G. W. Foster, M. Franklin, J. C. Freeman, Y. Fujii, I. Furic, A. Gajjar, M. Gallinaro, J. Galyardt, M. Garcia-Sciveres, A. F. Garfinkel, C. Gay, H. Gerberich, D. W. Gerdes, E. Gerchtein, S. Giagu, P. Giannetti, A. Gibson, K. Gibson, C. Ginsburg, K. Giolo, M. Giordani, M. Giunta, G. Giurgiu, V. Glagolev, D. Glenzinski, M. Gold, N. Goldschmidt, D. Goldstein, J. Goldstein, G. Gomez, G. Gomez-Ceballos, M. Goncharov, O. Gonzalez, I. Gorelov, A. T. Goshaw, Y. Gotra, K. Goulianos, A. Gresele, M. Griffiths, C. Grosso-Pilcher, U. Grundler, J. G. Da Costa, C. Haber, K. Hahn, S. R. Hahn, E. Halkiadakis, A. Hamilton, B. Y. Han, R. Handler, F. Happacher, K. Hara, M. Hare, R. F. Harr, R. M. Harris, F. Hartmann, K. Hatakeyama, J. Hauser, C. Hays, H. Hayward, B. Heinemann, J. Heinrich, M. Hennecke, M. Herndon, C. Hill, D. Hirschbuehl, A. Hocker, K. D. Hoffman, A. Holloway, S. Hou, M. A. Houlden, B. T. Huffman, Y. Huang, R. E. Hughes, J. Huston, K. Ikado, J. Incandela, G. Introzzi, M. Iori, Y. Ishizawa, C. Issever, A. Ivanov, Y. Iwata, B. Iyutin, E. James, D. Jang, B. Jayatilaka, D. Jeans, H. Jensen, E. J. Jeon, M. Jones, K. K. Joo, S. Y. Jun, T. Junk, T. Kamon, J. Kang, M. K. Unel, P. E. Karchin, Y. Kato, Y. Kemp, R. Kephart, U. Kerzel, V. Khotilovich, B. Kilminster, D. H. Kim, H. S. Kim, J. E. Kim, M. J. Kim, M. S. Kim, S. B. Kim, S. H. Kim, Y. K. Kim, M. Kirby, L. Kirsch, S. Klimenko, M. Klute, B. Knuteson, B. R. Ko, H. Kobayashi, D. J. Kong, K. Kondo, J. Konigsberg, K. Kordas, A. Korn, A. Korytov, A. V. Kotwal, A. Kovalev, J. Kraus, I. Kravchenko, A. Kreymer, J. Kroll, M. Kruse, V. Krutelyov, S. E. Kuhlmann, S. Kwang, A. T. Laasanen, S. Lai, S. Lami, S. Lammel, M. Lancaster, R. Lander, K. Lannon, A. Lath, G. Latino, I. Lazzizzera, C. Lecci, T. Lecompte, J. Lee, J. Lee, S. W. Lee, R. Lefevre, N. Leonardo, S. Leone, S. Levy, J. D. Lewis, K. Li, C. Lin, C. S. Lin, M. Lindgren, E. Lipeles, T. M. Liss, A. Lister, D. O. Litvintsev, T. Liu, Y. Liu, N. S. Lockyer, A. Loginov, M. Loreti, P. Loverre, R. S. Lu, D. Lucchesi, P. Lujan, P. Lukens, G. Lungu, L. Lyons, J. Lys, R. Lysak, E. Lytken, D. Macqueen, R. Madrak, K. Maeshima, P. Maksimovic, G. Manca, F. Margaroli, R. Marginean, C. Marino, A. Martin, M. Martin, V. Martin, M. Martinez, T. Maruyama, H. Matsunaga, M. Mattson, P. Mazzanti, K. S. Mcfarland, D. Mcgivern, P. M. Mcintyre, P. Mcnamara, R. Mcnulty, A. Mehta, S. Menzemer, A. Menzione, P. Merkel, C. Mesropian, A. Messina, T. Miao, N. Miladinovic, J. Miles, L. Miller, R. Miller, J. S. Miller, C. Mills, R. Miquel, S. Miscetti, G. Mitselmakher, A. Miyamoto, N. Moggi, B. Mohr, R. Moore, M. Morello, P. A. M. Fernandez, J. Muelmenstaedt, A. Mukherjee, M. Mulhearn, T. Muller, R. Mumford, A. Munar, P. Murat, J. Nachtman, S. Nahn, I. Nakano, A. Napier, R. Napora, D. Naumov, V. Necula, T. Nelson, C. Neu, M. S. Neubauer, J. Nielsen, T. Nigmanov, L. Nodulman, O. Norniella, T. Ogawa, S. H. Oh, Y. D. Oh, T. Ohsugi, T. Okusawa, R. Oldeman, R. Orava, W. Orejudos, K. Osterberg, C. Pagliarone, E. Palencia, R. Paoletti, V. Papadimitriou, A. A. Paramonov, S. Pashapour, J. Patrick, G. Pauletta, M. Paulini, C. Paus, D. Pellett, A. Penzo, T. J. Phillips, G. Piacentino, J. Piedra, K. T. Pitts, C. Plager, L. Pondrom, G. Pope, X. Portell, O. Poukhov, N. Pounder, F. Prakoshyn, A. Pronko, J. Proudfoot, F. Ptohos, G. Punzi, J. Rademacker, M. A. Rahaman, A. Rakitine, S. Rappoccio, F. Ratnikov, H. Ray, B. Reisert, V. Rekovic, P. Renton, M. Rescigno, F. Rimondi, K. Rinnert, L. Ristori, W. J. Robertson, A. Robson, T. Rodrigo, S. Rolli, R. Roser, R. Rossin, C. Rott, J. Russ, V. Rusu, A. Ruiz, D. Ryan, H. Saarikko, S. Sabik, A. Safonov, R. St Denis, W. K. Sakumoto, G. Salamanna, D. Saltzberg, C. Sanchez, L. Santi, S. Sarkar, K. Sato, P. Savard, A. Savoy-Navarro, P. Schlabach, E. E. Schmidt, M. P. Schmidt, M. Schmitt, T. Schwarz, L. Scodellaro, A. L. Scott, A. Scribano, F. Scuri, A. Sedov, S. Seidel, Y. Seiya, A. Semenov, F. Semeria, L. Sexton-Kennedy, I. Sfiligoi, M. D. Shapiro, T. Shears, P. F. Shepard, D. Sherman, M. Shimojima, M. Shochet, Y. Shon, I. Shreyber, A. Sidoti, A. Sill, P. Sinervo, A. Sisakyan, J. Sjolin, A. Skiba, A. J. Slaughter, K. Sliwa, D. Smirnov, J. R. Smith, F. D. Snider, R. Snihur, M. Soderberg, A. Soha, S. V. Somalwar, J. Spalding, M. Spezziga, F. Spinella, P. Squillacioti, H. Stadie, M. Stanitzki, B. Stelzer, O. Stelzer-Chilton, D. Stentz, J. Strologas, D. Stuart, J. S. Suh, A. Sukhanov, K. Sumorok, H. Sun, T. Suzuki, A. Taffard, R. Tafirout, H. Takano, R. Takashima, Y. Takeuchi, K. Takikawa, M. Tanaka, R. Tanaka, N. Tanimoto, M. Tecchio, P. K. Teng, K. Terashi, R. J. Tesarek, S. Tether, J. Thom, A. S. Thompson, E. Thomson, P. Tipton, V. Tiwari, S. Tkaczyk, D. Toback, K. Tollefson, T. Tomura, D. Tonelli, M. Tonnesmann, S. Torre, D. Torretta, S. Tourneur, W. Trischuk, R. Tsuchiya, S. Tsuno, D. Tsybychev, N. Turini, F. Ukegawa, T. Unverhau, S. Uozumi, D. Usynin, L. Vacavant, A. Vaiciulis, A. Varganov, S. Vejcik, G. Velev, V. Veszpremi, G. Veramendi, T. Vickey, R. Vidal, I. Vila, R. Vilar, I. Vollrath, I. Volobouev, M. Von Der Mey, P. Wagner, R. G. Wagner, R. L. Wagner, W. Wagner, R. Wallny, T. Walter, Z. Wan, M. J. Wang, S. M. Wang, A. Warburton, B. Ward, S. Waschke, D. Waters, T. Watts, M. Weber, W. C. Wester, B. Whitehouse, D. Whiteson, A. B. Wicklund, E. Wicklund, H. H. Williams, P. Wilson, B. L. Winer, P. Wittich, S. Wolbers, C. Wolfe, M. Wolter, M. Worcester, S. Worm, T. Wright, X. Wu, F. Wurthwein, A. Wyatt, A. Yagil, T. Yamashita, K. Yamamoto, J. Yamaoka, C. Yang, U. K. Yang, W. Yao, G. P. Yeh, J. Yoh, K. Yorita, T. Yoshida, I. Yu, S. Yu, J. C. Yun, L. Zanello, A. Zanetti, I. Zaw, F. Zetti, J. Zhou, S. Zucchelli

Department of Physics and Astronomy Faculty Publications

We present a measurement of the ratio of top-quark branching fractions R=B(t -> Wb)/B(t -> Wq), where q can be a b, s, or a d quark, using lepton-plus-jets and dilepton data sets with an integrated luminosity of similar to 162 pb(-1) collected with the Collider Detector at Fermilab during Run II of the Tevatron. The measurement is derived from the relative numbers of t (t) over bar events with different multiplicity of identified secondary vertices. We set a lower limit of R > 0.61 at 95% confidence level.

Beam-Helicity Asymmetries In Double-Charged-Pion Photoproduction On The Proton, H. Bagdasaryan, M. Bektasoglu, S. Bültmann, Gail Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. Klein, S. E. Kuhn, L. M. Qin, W. Roberts, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Yun, J. Zhang, Et Al., Clas Collaboration

Physics Faculty Publications

Beam-helicity asymmetries for the two-pion-photoproduction reaction 𝛾⃗p → p π⁺π^- have been studied for the first time in the resonance region for center-of-mass energies between 1.35 and 2.30 GeV. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer using circularly polarized tagged photons incident on an unpolarized hydrogen target. Beam-helicity-dependent angular distributions of the final-state particles were measured. The large cross-section asymmetries exhibit strong sensitivity to the kinematics and dynamics of the reaction. The data are compared with the results of various phenomenological model calculations, and show that these models currently do not …

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

Physics Faculty Publications

At high energies, the relevant degrees of freedom are Wilson lines—infinite gauge links ordered along straight lines collinear to the velocities of colliding particles. The effective action for these Wilson lines is determined by the scattering of QCD shock waves. I develop the symmetric expansion of the effective action in powers of strength of one of the shock waves and calculate the leading term of the series. The corresponding first-order effective action, symmetric with respect to projectile and target, includes both up and down fan diagrams and pomeron loops.

Today's Take On Einstein’S Relativity: Proceedings Of The Conference Of 18 Feb 2005, Florentin Smarandache, Homer B. Tilton

Branch Mathematics and Statistics Faculty and Staff Publications

Non Sequiturs in Relativity Four in number at this point Dr. Smith of "Lost in Space" had a knack of easing out of binds that he'd gotten himself into. Dr. Einstein was a little like that. Einstein originally declared that the distortions of special relativity reflect real changes to the objects being remotely observed, then reconsidered. The first non sequitur is quoted here from Sachs:[1] In a lecture that Einstein gave to the Prussian Academy of Sciences in 1921, he said the following: "Geometry predicates nothing about relations of real things, but only geometry together with the purport of physical …

Comparison Of Geant4 Electromagnetic Physics Models Against The Nist Reference Data, Katsuya Amako, Susanna Guatelli, Vladimir N. Ivanchencko, Michel Maire, Barbara Mascialino, Koichi Murakami, Petteri Nieminen, Luciano Pandola, Sandra Parlati, Maria Grazia Pia, Michela Piergentili, Takashi Sasaki, Laszlo Urban

Faculty of Engineering - Papers (Archive)

The Geant4 Simulation Toolkit provides an ample set of physics models describing electromagnetic interactions of particles with matter. This paper presents the results of a series of comparisons for the evaluation of Geant4 electromagnetic processes with respect to United States National Institute of Standards and Technologies (NIST) reference data. A statistical analysis was performed to estimate quantitatively the compatibility of Geant4 electromagnetic models with NIST data; the statistical analysis also highlighted the respective strengths of the different Geant4 models.

Physics Workshop Tutorials: Views Of Life-Science Students, Roger A. Lewis

Faculty of Engineering - Papers (Archive)

[extract] Physics workshop tutorials, their implementation, and the purpose of this research: Workshop tutorials involve small groups of students using hands-on demonstrations and answering questions under the auspices of a tutor. Physics education research underpinned the development of workshop tutorials (Sharma, Millar and Seth 1999; Wilson, Peseta, Sharma and Millar 2002). Greater attendance at workshop tutorials is correlated with better examination marks (Sharma et al. 1999).

Exclusive Photoproduction Of The Cascade Ξ Hyperons, H. Bagdasaryan, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. V. Klimenko, S. E. Kuhn, L. M. Qin, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

We report on the first measurement of exclusive Ξ^-(1321) hyperon photoproduction in 𝛾p → K⁺K⁺Ξ^- for 3.2 < E𝛾 < 3.9 GeV. The final state is identified by the missing mass in p(𝛾,K⁺K⁺)X measured with the CLAS detector at Jefferson Laboratory. We have detected a significant number of the ground state Ξ^-(1321)1/2⁺ and have estimated the total cross section for its production. We also have strong evidence for the first excited state Ξ^-(1530)3/2⁺. Photoproduction provides a copious source of Ξ's. We discuss the possibilities of a search for the recently proposed Ξ₅^- and Ξ₅^{+ …}