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Physics Faculty Publications

2010

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Articles 31 - 55 of 55

Full-Text Articles in Physical Sciences and Mathematics

Measurement Of Γ-Emission Branching Ratios For 154,156,158Gd Compound Nuclei: Tests Of Surrogate Nuclear Reaction Approximations For (N,Γ) Cross Sections, N. D. Scielzo Mar 2010

Measurement Of Γ-Emission Branching Ratios For 154,156,158Gd Compound Nuclei: Tests Of Surrogate Nuclear Reaction Approximations For (N,Γ) Cross Sections, N. D. Scielzo

Physics Faculty Publications

The surrogate nuclear reaction method can be used to determine neutron-induced reaction cross sections from measured decay properties of a compound nucleus created using a different reaction and calculated formation cross sections. The reliability of (n,γ) cross sections determined using the Weisskopf-Ewing and ratio approximations are explored for the 155, 157Gd(n,γ) reactions. Enriched gadolinium targets were bombarded with 22-MeV protons and γ rays were detected in coincidence with scattered protons using the Silicon Telescope Array for Reaction Studies/Livermore-Berkeley Array for Collaborative Experiments (STARS/LiBerACE) silicon and germanium detector arrays. The γ-emission probabilities for the 154, 156, …

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Radiation Emission From Wrinkled Sige/Sige Nanostructure, A. I. Fedorchenko, H. H. Cheng, Greg Sun, R. A. Soref Mar 2010

Radiation Emission From Wrinkled Sige/Sige Nanostructure, A. I. Fedorchenko, H. H. Cheng, Greg Sun, R. A. Soref

Physics Faculty Publications

Semiconductor optical emitters radiate light via band-to-band optical transitions. Here, a different mechanism of radiation emission, which is not related to the energy band of the materials, is proposed. In the case of carriers traveling along a sinusoidal trajectory through a wrinkled nanostructure, radiation was emitted via changes in their velocity in a manner analogous to synchrotron radiation. The radiated frequency of wrinkled SiGe/SiGe nanostructure was found to cover a wide spectrum with radiation power levels of the order of submilliwatts. Thus, this nanostructure can be used as a Si-based optical emitter and it will enable the integration of optoelectronic …

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Optical Caustics Observed In Light Scattered By An Oblate Spheroid, James A. Lock, Feng Xu Mar 2010

Optical Caustics Observed In Light Scattered By An Oblate Spheroid, James A. Lock, Feng Xu

Physics Faculty Publications

The electromagnetic fields scattered when a plane wave is incident on an oblate spheroid in the side-on orientation may be calculated using a generalization of Mie theory, and the results may be decomposed in a Debye series expansion. A number of optical caustics are observed in the computed scattered intensity for the one internal reflection portion of the Debye series for scattering angles in the vicinity of the first-order rainbow, and are analyzed in terms of the rainbow, transverse cusp, and hyperbolic umbilic caustics of catastrophe optics. The specific features of these three caustics are described, as is their assembly …

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High-Energy Amplitudes In N= 4 Sym In The Next-To-Leading Order, Ian Balitsky, Giovanni A. Chirilli Mar 2010

High-Energy Amplitudes In N= 4 Sym In The Next-To-Leading Order, Ian Balitsky, Giovanni A. Chirilli

Physics Faculty Publications

The high-energy behavior of the N = 4 SYM amplitudes in the Regge limit can be calculated order by order in perturbation theory using the high-energy operator expansion in Wilson lines. At large Nc , a typical four-point amplitude is determined by a single BFKL pomeron. The conformal structure of the four-point amplitude is fixed in terms of two functions: pomeron intercept and the coefficient function in front of the pomeron (the product of two residues). The pomeron intercept is universal while the coefficient function depends on the correlator in question. The intercept is known in the first two orders …

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Differential Cross Section And Recoil Polarization Measurements For The Γp→K+Λ Reaction Using Clas At Jefferson Lab, M. E. Mccracken, Gerard P. Gilfoyle, Et. Al. Feb 2010

Differential Cross Section And Recoil Polarization Measurements For The Γp→K+Λ Reaction Using Clas At Jefferson Lab, M. E. Mccracken, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

We present measurements of the differential cross section and 'B; recoil polarization for the γp → K+Λ reaction made using the CLAS detector at Jefferson Lab. These measurements cover the center-of-mass energy range from 1.62 to 2.84 GeV and a wide range of center-of-mass K+ production angles. Independent analyses were performed using the K+pπ− and K+p (missing π−) final-state topologies; results from these analyses were found to exhibit good agreement. These differential-cross-section measurements show excellent agreement with previous CLAS and LEPS results and offer increased precision and a 300-MeV increase …

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Mobility Analysis Of Highly Conducting Thin Films: Application To Zno, David C. Look, K. D. Leedy, D. H. Tomich, B. Bayraktaroglu Feb 2010

Mobility Analysis Of Highly Conducting Thin Films: Application To Zno, David C. Look, K. D. Leedy, D. H. Tomich, B. Bayraktaroglu

Physics Faculty Publications

Hall-effect measurements have been performed on a series of highly conductive thin films of Ga-doped ZnO grown by pulsed laser deposition and annealed in a forming-gas atmosphere (5% H2 in Ar). The mobility as a function of thickness d is analyzed by a simple formula involving only ionized-impurity and boundary scattering and having a single fitting parameter, the acceptor/donor concentration ratio K = NA/ND. For samples with d = 3–100 nm, Kavg = 0.41, giving ND = 4.7×1020 and NA = 1.9×1020 cm−3. Thicker samples require a …

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Structural Investigations And Magnetic Properties Of Sol-Gel Ni0.5zn0.5fe2o4 Thin Films For Microwave Heating, Pengzhao Z. Gao, Evgeny V. Rebrov, Tiny M. W. G. M. Verhoeven, Jaap C. Schouten, Richard Kleismit, Gregory Kozlowski, John S. Cetnar, Zafer Turgut, Guru Subramanyam Feb 2010

Structural Investigations And Magnetic Properties Of Sol-Gel Ni0.5zn0.5fe2o4 Thin Films For Microwave Heating, Pengzhao Z. Gao, Evgeny V. Rebrov, Tiny M. W. G. M. Verhoeven, Jaap C. Schouten, Richard Kleismit, Gregory Kozlowski, John S. Cetnar, Zafer Turgut, Guru Subramanyam

Physics Faculty Publications

Nanocrystalline Ni0.5Zn0.5Fe2O4 thin films have been synthesized with various grain sizes by a sol-gel method on polycrystalline silicon substrates. The morphology, magnetic, and microwave absorption properties of the films calcined in the 673–1073 K range were studied with x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy, atomic force microscopy, vibrating sample magnetometry, and evanescent microwave microscopy. All films were uniform without microcracks. Increasing the calcination temperature from 873 to 1073 K and time from 1 to 3 h resulted in an increase of the grain size from 12 to 27 nm. The saturation …

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Fission Fragment Isomers Populated Via 6Li+232Th., J. J. Ressler, J. A. Caggiano, C. J. Francy, P. N. Peplowski, J. M. Allmond, C. W. Beausang, L. A. Bernstein, D. L. Bleuel, J. T. Burke, P. Fallon, A. A. Hecht, D. V. Jordan, S. R. Lesher, M. A. Mcmahan, T. S. Palmer, L. Phair, N. D. Scielzo, P. G. Swearingen, G. A. Warren, M. Wiedeking Jan 2010

Fission Fragment Isomers Populated Via 6Li+232Th., J. J. Ressler, J. A. Caggiano, C. J. Francy, P. N. Peplowski, J. M. Allmond, C. W. Beausang, L. A. Bernstein, D. L. Bleuel, J. T. Burke, P. Fallon, A. A. Hecht, D. V. Jordan, S. R. Lesher, M. A. Mcmahan, T. S. Palmer, L. Phair, N. D. Scielzo, P. G. Swearingen, G. A. Warren, M. Wiedeking

Physics Faculty Publications

Short-lived isomers in fission fragments following bombardment of 45-MeV 6Li on 232Th were examined. Isomers in the A ~ 95,122, and 132 mass regions were observed. New isomeric decays were observed in 121In [T1/2=17(2) μs], 123In (T1/2≳100 μs), and 125Sb [T1/2=25(4) μs]. These isomers are suggested to arise from ν(h11/2⊗d3/2)7−and ν(h11/2⊗s1/2)5− neutron core excitations coupling with the valence proton.

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Demonstration Of A Neutral Atom Controlled-Not Quantum Gate, L. Isenhower, E. Urban, X. L. Zhang, A. T. Gill, T. Henage, Todd A. Johnson, T. G. Walker, M. Saffman Jan 2010

Demonstration Of A Neutral Atom Controlled-Not Quantum Gate, L. Isenhower, E. Urban, X. L. Zhang, A. T. Gill, T. Henage, Todd A. Johnson, T. G. Walker, M. Saffman

Physics Faculty Publications

We present the first demonstration of a CNOT gate between two individually addressed neutral atoms. Our implementation of the CNOT uses Rydberg blockade interactions between neutral atoms held in optical traps separated by >8  μm. Using two different gate protocols we measure CNOT fidelities of F=0.73 and 0.72 based on truth table probabilities. The gate was used to generate Bell states with fidelity F=0.48±0.06. After correcting for atom loss we obtain an a posteriori entanglement fidelity of F=0.58.

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Interplay Between The Lattice And Spin Degrees Of Freedom In (Sr1−Xcax)3ru2o7, Jin Peng, David Fobes, Tijian Liu, Xiaoshan Wu, H M. Pham, Leonard Spinu, Z Q. Mao Jan 2010

Interplay Between The Lattice And Spin Degrees Of Freedom In (Sr1−Xcax)3ru2o7, Jin Peng, David Fobes, Tijian Liu, Xiaoshan Wu, H M. Pham, Leonard Spinu, Z Q. Mao

Physics Faculty Publications

The Sr1−xCax3Ru2O7 solid solution series exhibits complex magnetic ground states, ranging from an itinerant metamagnetic state, to a quasi-two-dimensional 2D heavy-mass nearly ferromagneticFM state, and finally to a long-range antiferromagnetically ordered state Z. Qu et al. Phys. Rev. B. 78, R180407 2008. In this paper, we investigate the evolution of structural distortion and magnetic anisotropy with Ca content in this material system. Our results show that both the magnetic phase transitions and magnetic anistropy of this system couple with the evolution of structure distortion. The transformation from the itinerant metamagnetic to the nearly ferromagnetic state is accompanied …

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Fabrication And Magnetic Properties Of Fe Nanostructures In Anodic Alumina Membrane, J H. Lim, W S. Chae, H O. Lee, L Malkinski, S G. Min, J B. Wiley, J H. Jun, S H. Lee, J S. Jung Jan 2010

Fabrication And Magnetic Properties Of Fe Nanostructures In Anodic Alumina Membrane, J H. Lim, W S. Chae, H O. Lee, L Malkinski, S G. Min, J B. Wiley, J H. Jun, S H. Lee, J S. Jung

Physics Faculty Publications

Several Fe nanostructures with different lengths, diameters, and separations of the constituting magnetic components have been synthesized using anodized alumina membranes (AAMs) to understand the influence of these parameters on their magnetic properties. Fe nanostructures with high crystallinity and (110) orientation were synthesized by electrodeposition at room temperature in regular AAMs and mild-hard AAM (Mi-Ha AAM). Fe nanostructures with different aspect ratios (1:1, 1:10, and 1:75) in the form of nanodots, nanorods, or nanowires were synthesized in regular AAMs with the 100 nm interpore distance. Mi-Ha AAMs with two different pore sizes (70 and 120 nm) and 250 nm interpore …

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Collinear Phase Matching For Second Harmonic Generation Using Conoscopic Interferometry, A Puri, A De Jan 2010

Collinear Phase Matching For Second Harmonic Generation Using Conoscopic Interferometry, A Puri, A De

Physics Faculty Publications

The problem of finding phase-matching directions in noncentrosymmetric biaxial crystals is simplified here by the use of Conoscopic interferometry. Based on vector relations for wave propagation in birefringent media and solutions to phase-matching equations, we show that phase matching directions can be located on the conoscopic interferograms and that fringe numbers for dark-isochromes can be used as a guide to find phase-matching directions for a biaxial crystal. This technique can be generalized and extended to any anisotropic crystal. We have demonstrated this method for the particular case of a biaxial KTiOPO4 crystal, where it is found to be particularly …

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Mapping The Distribution Of Electron Temperature And Fe Charge States In The Corona With Total Solar Eclipse Observations, Shadia Rifai Habbal, Miloslav Druckmüller, Huw Morgan, Adrian Daw, Judd Johnson, A. Ding, Martina Arndt, R. Esser, V. Rusin, I. Scholl Jan 2010

Mapping The Distribution Of Electron Temperature And Fe Charge States In The Corona With Total Solar Eclipse Observations, Shadia Rifai Habbal, Miloslav Druckmüller, Huw Morgan, Adrian Daw, Judd Johnson, A. Ding, Martina Arndt, R. Esser, V. Rusin, I. Scholl

Physics Faculty Publications

The inference of electron temperature from the ratio of the intensities of emission lines in the solar corona is valid only when the plasma is collisional. Once collisionless, thermodynamic ionization equilibrium no longer holds, and the inference of an electron temperature and its gradient from such measurements is no longer valid. At the heliocentric distance where the transition from a collision-dominated to a collisionless plasma occurs, the charge states of different elements are established, or frozen-in. These are the charge states which are subsequently measured in interplanetary space. We show in this study how the 2006 March 29 and 2008 …

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Total Solar Eclipse Observations Of Hot Prominence Shrouds, Shadia Rifai Habbal, Miloslav Druckmüller, Huw Morgan, I. Scholl, V. Rusin, Adrian Daw, Judd Johnson, Martina B. Arndt Jan 2010

Total Solar Eclipse Observations Of Hot Prominence Shrouds, Shadia Rifai Habbal, Miloslav Druckmüller, Huw Morgan, I. Scholl, V. Rusin, Adrian Daw, Judd Johnson, Martina B. Arndt

Physics Faculty Publications

Using observations of the corona taken during the total solar eclipses of 2006 March 29 and 2008 August 1 in broadband white light and in narrow bandpass filters centered at Fe x 637.4 nm, Fe xi 789.2 nm, Fe xiii 1074.7 nm, and Fe xiv 530.3 nm, we show that prominences observed off the solar limb are enshrouded in hot plasmas within twisted magnetic structures. These shrouds, which are commonly referred to as cavities in the literature, are clearly distinct from the overlying arch-like structures that form the base of streamers. The existence of these hot shrouds had been predicted …

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Hard Photodisintegration Of A Proton Pair, I. Pomerantz, N. Bubis, K. Allada, A. Beck, B. L. Berman, W. Boeglin, A. Camsonne, M. Canan, K. Chirapatpimol, E. Cisbani Jan 2010

Hard Photodisintegration Of A Proton Pair, I. Pomerantz, N. Bubis, K. Allada, A. Beck, B. L. Berman, W. Boeglin, A. Camsonne, M. Canan, K. Chirapatpimol, E. Cisbani

Physics Faculty Publications

We present a study of high energy photodisintegration of proton-pairs through the γ + 3He → p + p + n channel. Photon energies, Eγ , from 0.8 to 4.7 GeV were used in kinematics corresponding to a proton pair with high relative momentum and a neutron nearly at rest. The s−11 scaling of the cross section, as predicted by the constituent counting rule for two nucleon photodisintegration, was observed for the first time. The onset of the scaling is at a higher energy and the cross section is significantly lower than for deuteron (pn pair) photodisintegration. …

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Use Of Optical Tweezers To Probe Epithelial Mechanosensation, Andrew Resnick Jan 2010

Use Of Optical Tweezers To Probe Epithelial Mechanosensation, Andrew Resnick

Physics Faculty Publications

Cellular mechanosensation mechanisms have been implicated in a variety of disease states. Specifically in renal tubules, the primary cilium and associated mechanosensitive ion channels are hypothesized to play a role in water and salt homeostasis, with relevant disease states including polycystic kidney disease and hypertension. Previous experiments investigating ciliary-mediated cellular mechanosensation have used either fluid flow chambers or micropipetting to elicit a biological response. The interpretation of these experiments in terms of the "ciliary hypothesis" has been difficult due the spatially distributed nature of the mechanical disturbance-several competing hypotheses regarding possible roles of primary cilium, glycocalyx, microvilli, cell junctions, and …

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Excitation-Induced Germanium Quantum Dot Formation On Si (100)-(2×1), Ali Oguz Er, Hani E. Elsayed-Ali Jan 2010

Excitation-Induced Germanium Quantum Dot Formation On Si (100)-(2×1), Ali Oguz Er, Hani E. Elsayed-Ali

Physics Faculty Publications

The effect of nanosecond pulsed laser excitation on the self-assembly of Ge quantum dots grown by pulsed laser deposition on Si (100)-(2×1) was studied. In situ reflection high-energy electron diffraction and ex situ atomic force microscopy were used to probe the quantum dot structure and morphology. At room temperature, applying the excitation laser decreased the surface roughness of the grown Ge film. With surface electronic excitation, crystalline Ge quantum dots were formed at 250 °C, a temperature too low for their formation without excitation. At a substrate temperature of 390 °C, electronic excitation during growth was found to improve the …

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Infrared Skin Damage Thresholds From 1940-Nm Continuous-Wave Laser Exposures, Jeffrey W. Oliver, David J. Stolarski, Gary D. Noojin, Harvey M. Hodnett, Corey A. Harbert, Kurt J. Schuster, Michaedl F. Foltz, Semih S. Kumru, Clarence P. Cain, C. J. Finkeldei, Gavin Buffington, Isaac D. Noojin, Robert J. Thomas Jan 2010

Infrared Skin Damage Thresholds From 1940-Nm Continuous-Wave Laser Exposures, Jeffrey W. Oliver, David J. Stolarski, Gary D. Noojin, Harvey M. Hodnett, Corey A. Harbert, Kurt J. Schuster, Michaedl F. Foltz, Semih S. Kumru, Clarence P. Cain, C. J. Finkeldei, Gavin Buffington, Isaac D. Noojin, Robert J. Thomas

Physics Faculty Publications

A series of experiments are conducted in vivo using Yucatan mini-pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1940-nm continuous-wave thulium fiber laser irradiation. Experiments employ exposure durations from 10 ms to 10 s and beam diameters of approximately 4.8 to 18 mm. Thermal imagery data provide a time-dependent surface temperature response from the laser. A damage endpoint of minimally visible effect is employed to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Results are compared …

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Design Sensitivities Of The Superconducting Parallel-Bar Cavity, Subashini U. De Silva, Jean Delayen Jan 2010

Design Sensitivities Of The Superconducting Parallel-Bar Cavity, Subashini U. De Silva, Jean Delayen

Physics Faculty Publications

The superconducting parallel-bar cavity has properties that makes it attractive as a deflecting or crabbing rf structure. For example it is under consideration as an rf separator for the Jefferson Lab 12 GeV upgrade and as a crabbing structure for a possible LHC luminosity upgrade. In order to maintain the purity of the deflecting mode and avoid mixing with the near accelerating mode caused by geometrical imperfection, a minimum frequency separation is needed which depends on the expected deviations from perfect symmetry. We have done an extensive analysis of the impact of several geometrical imperfections on the properties of the …

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Applications Of Spoke Cavities, Jean R. Delayen Jan 2010

Applications Of Spoke Cavities, Jean R. Delayen

Physics Faculty Publications

The superconducting spoke cavity was introduced in the late 1980s in response to the need for superconducting structures in the mid-velocity range. Since then it has found application in many projects. Prototypes have been developed for a wide range of beam velocities. The characteristics and features of the spoke cavity are reviewed and some of their applications are presented.

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Plasma Treatment Of Bulk Niobium Surface For Superconducting Rf Cavities: Optimization Of The Experimental Conditions On Flat Samples, M. Rašković, J. Upadhyay, L. Vuskovic, S. Popovic, A.-M. Valente-Feliciano, L. Phillips Jan 2010

Plasma Treatment Of Bulk Niobium Surface For Superconducting Rf Cavities: Optimization Of The Experimental Conditions On Flat Samples, M. Rašković, J. Upadhyay, L. Vuskovic, S. Popovic, A.-M. Valente-Feliciano, L. Phillips

Physics Faculty Publications

Accelerator performance, in particular the average accelerating field and the cavity quality factor, depends on the physical and chemical characteristics of the superconducting radio-frequency (SRF) cavity surface. Plasma based surface modification provides an excellent opportunity to eliminate nonsuperconductive pollutants in the penetration depth region and to remove the mechanically damaged surface layer, which improves the surface roughness. Here we show that the plasma treatment of bulk niobium (Nb) presents an alternative surface preparation method to the commonly used buffered chemical polishing and electropolishing methods. We have optimized the experimental conditions in the microwave glow discharge system and their influence on …

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Longitudinal Scaling Property Of The Charge Balance Function In Au + Au Collisions At √Snn= 200 Gev, B. I. Abelev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, B. D. Anderson, D. Arkhipkin, G. S. Averichev, J. Balewski, L. S. Barnby, S. Bültmann, I. Koralt, D. Plyku Jan 2010

Longitudinal Scaling Property Of The Charge Balance Function In Au + Au Collisions At √Snn= 200 Gev, B. I. Abelev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, B. D. Anderson, D. Arkhipkin, G. S. Averichev, J. Balewski, L. S. Barnby, S. Bültmann, I. Koralt, D. Plyku

Physics Faculty Publications

We present measurements of the charge balance function, from the charged particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au collisions at √sNN = 200 GeV using the STAR detector at RHIC. We observe that the balance function is boost-invariant within the pseudorapidity coverage [ − 1.3 , 1.3 ] . The balance function properly scaled by the width of the observed pseudorapidity window does not depend on the position or size of the pseudorapidity window. This scaling property also holds for particles in different transverse momentum ranges. In addition, we find that the width …

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The Local Structure Of Transition Metal Doped Semiconducting Boron Carbides, Jing Liu, Guangfu Luo, Wai-Ning Mei, Orhan Kizilkaya, Eric D. Shepherd, J. I. Brand, Peter A. Dowben Jan 2010

The Local Structure Of Transition Metal Doped Semiconducting Boron Carbides, Jing Liu, Guangfu Luo, Wai-Ning Mei, Orhan Kizilkaya, Eric D. Shepherd, J. I. Brand, Peter A. Dowben

Physics Faculty Publications

Transition metal doped boron carbides produced by plasma enhanced chemical vapour deposition of orthocarborane (closo-1,2-C2B10H12) and 3d metal metallocenes were investigated by performing K-edge extended x-ray absorption fine structure and x-ray absorption near edge structure measurements. The 3d transition metal atom occupies one of the icosahedral boron or carbon atomic sites within the icosahedral cage. Good agreement was obtained between experiment and models for Mn, Fe and Co doping, based on the model structures of two adjoined vertex sharing carborane cages, each containing a transition metal. The local spin configurations of all …

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Measurement Of Single- And Double-Spin Asymmetries In Deep Inelastic Pion Electroproduction With A Longitudinally Polarized Target, H. Avakian, P. Bosted, V. D. Burkert, L. Elouadrhiri, K. P. Adhikari, M. Aghasyan, M. Amaryan, M. Anghinolfi, H. Baghdasaryan, J. Ball, G. Dodge, G. Gavalian, N. Guler, A. Klein, S E. Kuhn, D. Martinez, M. R. Niroula, F. Sabatié, H. Seraydaryan, S. Tkachenko, L. B. Weinstein Jan 2010

Measurement Of Single- And Double-Spin Asymmetries In Deep Inelastic Pion Electroproduction With A Longitudinally Polarized Target, H. Avakian, P. Bosted, V. D. Burkert, L. Elouadrhiri, K. P. Adhikari, M. Aghasyan, M. Amaryan, M. Anghinolfi, H. Baghdasaryan, J. Ball, G. Dodge, G. Gavalian, N. Guler, A. Klein, S E. Kuhn, D. Martinez, M. R. Niroula, F. Sabatié, H. Seraydaryan, S. Tkachenko, L. B. Weinstein

Physics Faculty Publications

We report the first measurement of the transverse momentum dependence of double-spin asymmetries in semi-inclusive production of pions in deep-inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Jefferson Lab (JLab). Modulations of single spin asymmetries over the azimuthal angle between lepton scattering and hadron production planes ϕ have been measured over a wide kinematic range in Bjorken x and virtual photon squared four-momentum Q2. A significant nonzero sin2ϕ single spin asymmetry was observed for the first time indicating strong spin-orbit correlations …

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Parton Energy Loss In Heavy-Ion Collisions Via Direct-Photon And Charged-Particle Azimuthal Correlations, B. I. Abelev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, B. D. Anderson, D. Arkhipkin, G. S. Averichev, S. Bueltmann, I. Koralt, Star Collaboration Jan 2010

Parton Energy Loss In Heavy-Ion Collisions Via Direct-Photon And Charged-Particle Azimuthal Correlations, B. I. Abelev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, B. D. Anderson, D. Arkhipkin, G. S. Averichev, S. Bueltmann, I. Koralt, Star Collaboration

Physics Faculty Publications

Charged-particle spectra associated with direct photon Ydir) and π0 are measured in p+p and Au+Au collisions at center-of-mass energy √sNN=200 GeV with the STAR detector at the Relativistic Heavy Ion Collider. A shower-shape analysis is used to partially discriminate between Ydirand π0. Assuming no associated charged particles in the γdir direction (near side) and small contribution from fragmentation photons (Yfrag), the associated charged-particle yields opposite to Ydir(away side) are extracted. In central Au+Au collisions, the charged-particle yields at midrapidity (|η|<1) and high transverse momentum (3 < PTassoc < 16 GeV/c) associated with γdir and π0 (|η|<0.9, 8 < PTtrig <16 GeV/c) are suppressed by a factor of 3–5 compared with p+p collisions. The observed suppression of the associated charged particles is similar for Ydir and π0 and …

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