Physics Commons^™

Search For Electroweak Production Of Single Top Quarks In Pp̅ Collisions, B. Abbott

Gregory Snow Publications

We present a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ≈90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the D Ø detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process pp̅→tb+X of 39 pb. The upper limit for the t-channel processpp̅→tqb+X …

Perspectives Of Giant Magnetoresistance, Evgeny Y. Tsymbal, David G. Pettifor

Evgeny Tsymbal Publications

Giant magnetoresistance (GMR) is one of the most fascinating discoveries in thin-film magnetism, which combines both tremendous technological potential and deep fundamental physics. Within a decade of GMR being discovered in 1988 commercial devices based on this phenomenon, such as hard-disk read-heads, magnetic field sensors and magnetic memory chips, had become available in the market. These achievements would not have been possible without a detailed understanding of the physics of GMR, which requires a quantum-mechanical insight into the electronic spin-dependent transport in magnetic structures.

Growth, Structure, Electronic, And Magnetic Properties Of Mgo/Fe(001) Bilayers And Fe/Mgo/Fe(001) Trilayers, M. Klaua, D. Ullmann, J. Barthel, W. Wulfhekel, J. Kirschner, R. Urban, Theodore L. Monchesky, Axel Enders, John F. Cochran, Brett Heinrich

Axel Enders Publications

Single-crystal epitaxial MgO thin films were grown directly onto high-quality Fe single crystal and Fe whisker substrates and covered with Fe/Au layers. Reflection high-energy electron diffraction and low-energy electron diffraction patterns and scanning tunneling microscopy images showed that the growth of MgO proceeded pseudomorphically in a nearly layer-by-layer mode up to six monolayers. A misfit dislocation network is formed for MgO layers thicker than six monolayers. The thin MgO films were characterized electrically by scanning tunneling spectroscopy. The tunneling barrier in MgO was found to depend on the MgO layer thickness, starting from 2.5 eV at two monolayer thickness to …

Tracking Of Moving Objects In Scenery Using Subspace Projection Using Independent Component Analysis, Brian J. Noe, Fredric M. Ham

Aerospace, Physics, and Space Science Faculty Publications

A system is developed for tracking moving objects though natural scenery. A technique is presented for performing change detection on imagery to determine the difference between two images or a sequence of images. Form there an algorithm is presented to detect the presence of a new object and/or the deletion of objects. Then the application of a Variable Structure Interacting Multiple Model tracking filter is presented. The method of performing change detection is based upon the concept of image subspace projection. A set of basis image maps are formed when combined with a mixing matrix can recreate the original image. …

Optical Absorption And Photoluminescence Measurements In Inp And Inp:Fe Bulk Crystals And Inspection Of The Relations Between These Measurements, Seydi̇ Doğan, Sebahatti̇n Tüzemen, Beki̇r Gürbulak, Aytunç Ateş, Muhammet Yildirim

Turkish Journal of Physics

Optical absorption and photoluminescence (PL) measurements were carried out in both undoped and Fe-doped samples and the effect of Fe doping on absorption and PL spectra were studied. The results show that Fe or Fe-related defects behave as non-radiative recombination centers in InP. This is very important from the point of view that the control of minority carrier lifetime is possible. On the other hand, comparative analysis of the PL results with the optical absorption data show that quantitative assessment of relative PL intensities is possible with respect to Fe concentrations.

Directional Solidification Of Pure Succinonitrile And Succinonitrile- Salol Alloys, İbrahi̇m Karaca, Emi̇n Çadirli, Hasan Kaya, Necmetti̇n Maraşli

Turkish Journal of Physics

Pure succinonitrile (SCN) and succinonitrile-salol alloys with four different concentrations of salol were unidirectionally solidified at five different growth rates in a temperature gradient. The microstructure parameters, viz., the primary dendrite arm spacing \lambda _{1}, dendrite tip radius R and mushy zone depth d, were measured. The dependence of the microstructure parameters on the solidification parameters for pure SCN and SCN-Salol alloys were determined via linear regression analysis. The results are compared with published data.

Field And Polarization Effects Arising In Neutrino-Lepton Processes In A Magnetic Field, V. A. Gusseinov

Turkish Journal of Physics

We discuss the effects arising in the neutrino-lepton processes (\nu_{\mu}+e^{-} \rightarrow \nu_{e}+\mu^{-} and \overline{\nu}_{e}+e^{-}\rightarrow\overline{\nu}_{\mu}+\mu^{-}) in a constant uniform magnetic field in the framework of the Weinberg-Salam-Glashow model. It is shown that in the case of a superstrong magnetic field and for the muon producing on the ground Landau level the leading term of the cross section asymptotics of the \nu_{\mu}-process does not depend on the field intensity and it effectively describes the one-dimensional free process. In the \nu_{\mu}-process the muons with the spins oriented opposite to the direction of the field are mostly produced. The electrons with the spins oriented …

The Resonance Bremsstrahlung Of A Fast Charged Particle In A Medium, Khamidbi M. Beshtoev

Turkish Journal of Physics

The bremsstrahlung of a fast charged particle in the medium with dielectric permittivity \epsilon at velocities v \ge \frac{c}{n} (\mbox{Re}\epsilon = n^2) was considered. Bremsstrahlung radiation has singularity at \beta = \frac{1}{n \cos\theta} (\beta = \frac{v}{c}, \theta is an angle of the bremsstrahlung.) and is interpreted as resonance bremsstrahlung with the width characterized by Im\epsilon = \epsilon_2; and smaller \epsilon_2 is, the higher the peak of the resonance. The angle distribution of the bremsstrahlung is determined by \cos \theta = \frac{1}{n\beta} and \theta coincides with the angle of Cherenkov radiation. At \beta = \frac{1}{n} the resonance bremsstrahlung goes in the …

Magnetoresistance Measurements On Electrodeposited Co_X Cu_{1-X} Alloy Films, Ömer F. Bakkaloğlu, İsmai̇l H. Karahan

Turkish Journal of Physics

Co_x Cu_{1-x} alloy films were prepared by using electrodeposition technique. The variations of Co and Cu contents of the films were investigated as functions of bath pH and Co content. The compositions of the alloy films were determined using an atomic absorption spectrophotometer. The crystal structures of the alloy films were analyzed using a Cu (K \alpha )-X-ray diffractometer. The diffraction lines observed were only those of copper component in the alloy films. All three films showed negative magnetoresistance and a giant magnetoresistance effect on the order of 1% in Co_{0.26} Cu_{0.74} and 1.7% in Co_{0.19} Cu_{0.81} alloy films at …

Multiple Structures Of (110) Csl Twist Boundaries In Fcc Metals, A. Ghafoor, B. A. S. Faridi, S. A. Ahmad

Turkish Journal of Physics

The geometry of different possible structures of (110) fcc twist boundaries is explored. Computer simulation of all possible low energy structures have been carried out for \Sigma=3 and \Sigma=9 twist boundaries using many-body potentials representing copper, silver and gold. Low symmetry structures are found to have lower energies than the high symmetry CSL structures.

Properties Of Mos Capacitors Produced On Sige Formed By Ge-Implanted Si, M. Şahi̇n, Serhat Özder, Raşi̇t Turan

Turkish Journal of Physics

Metal-oxide-semiconductor (MOS) capacitors fabricated on Ge-implanted Si have been investigated by using C-V and G-V measurements. The control sample on pure Si substrate yielded normal C-V and G-V characteristics. The Ge-implanted MOS samples exhibited anomalous C-V and G-V behavior. The C-V curves of the samples were strongly frequency dependent both in the accumulation and inversion regions. They shift almost in parallel to higher values with decreasing frequency, reaching the oxide capacitance value in the quasi-static (QS) measurement. A band structure and equivalent circuit model were introduced to explain this and other features of the experimental observations. It is shown that …

A Novel Technique For The Preparation Of Textured Yba_{2}Cu_{3}O_{7-\Delta} Superconductor, Naheed Kouser, Saadat Anwar Siddiqi, Asghari Maqsood

Turkish Journal of Physics

Textured samples having composition of YBa_{2}Cu_{3}O_{7-\delta} were prepared by using a novel technique of heating the samples in a thermal gradient which varies linearly between 930-950 ^oC over a distance of 5 cm. The samples were characterized by X-ray powder diffraction analysis, temperature dependent resistivity and magnetic susceptibility measurements, and scanning electron microscopy. XRD analysis shows that sample heated between 930-935 ^oC has tetragonal symmetry and all other three samples show orthorhombic symmetry. Samples heated in temperature gradient of 935-945 ^oC aligned along the c-axis. The orthorhombic samples exhibited zero resistance above 86K with short transition width and samples heated …

Successive Toroidal Compactifications Of A Closed Bosonic Strings, N. Mebarki, A. Taleb, H. Aissaoui, Nadir Belaloui, M. Haouchine

Turkish Journal of Physics

Successive toroidal compactifications of a closed bosonic string are studied and some Lie groups solutions are derived.

Zeros Of Scattering Amplitude For A Spin-Dependent Gaussian Potential, Nilufar Farhat Hossain, Hasna Banu, A. K. Halder

Turkish Journal of Physics

In the proposed model, polarization in the scattering amplitude for a Gaussian potential including spin is considered. The problem of scattering amplitude is formulated in two different ways: the first and second Born approximations along with their high energy limits and the eikonal approximation including Wallace corrections. A comparison of the numerical zeros of the scattering amplitude computed in the above two approximations is studied in the complex momentum transfer plane. An analysis of the zero trajectories shows that the contribution of the spin part in the potential is quite significant at high energies whereas at low energies the spin-part …

Beta Spectrometers With Surface Barrier Detector And Plastic Scintillator: Applications To ^{90}Sr,^{204}Tl,^{210}Pb And ^{14}C, Cüneyt Çeli̇ktaş

Turkish Journal of Physics

In this work, a comparison of responses between a spectrometer using Si Surface Barrier Detector (Si SBD) and a spectrometer using Plastic Scintillator (PS) is given. Experimental pulse height spectra of beta particles from ^{90}Sr,^{204}Tl,^{210}Pb and ^{14}C pure beta sources has been obtained separately. By comparing obtained spectra, the priority of obtaining the beta spectra among them is discussed. This work is related to the spectral response of beta spectrometers to pure beta sources.

Features Of The Compound Multiplicity Of The Interactions Of ^{24}Mg And ^{28}Si Ions With Emulsion Nuclei At 4.5a Gev/C, N. N. Abd-Allah, M. Mohery

Turkish Journal of Physics

The present paper deals with the interactions of ^{24}Mg and ^{28}Si nuclei at 4.5A GeV/c with emulsion. Some characteristics of the compound multiplicity given by the numerical sum of grey and shower particles have been investigated. The obtained results indicate that the compound multiplicity distribution is consistent with KNO-Scaling and its width increases with the size of the projectile nucleus.The dependence of the average compound multiplicity on the numbers of black and the grey particles and the sum of them is obvious and the values of the slope has been found to be independent of the projectile nucleus.

Multiparticle Equations For Scalar Particles, Valery Nikolaevich Kapshai, Alexander Ivanovich Fursin

Turkish Journal of Physics

Multiparticle equations for scalar particles are derived in the framework of the Lagrangian formalism of field theory as a consequence of the Dyson-Schwinger equations for the generating functional of Green's functions. The general form of the n-particle equation is determined. The formula for the kernel of the equation is obtained. It makes possible to use the functional methods for the investigation of the equation. It is proven that the equation is correct in the lower orders for two-particle Green's functions.

Mössbauer-Effect Study Of Fine Atomic Structure Of Fe-Ni-C Alloys, K. G. Binnatov, A. O. Mekhrabov

Turkish Journal of Physics

Fine atomic structure of Fe-Ni-C alloys containing of 30-36 wt. % Ni and 0.1-1.0 wt. % C have been analysed by means of a nuclear \gamma -resonance method. The alloys under investigation were in austenite phase. The study shows that the effective hyperfine magnetic field H_{eff} on the ^{57}Fe nuclei is affected by the presence of C atoms in Fe-Ni alloys and the mean value of H_{eff} fields increase with increasing of C element content in these alloys. It has been detected that increase in carbon content in Fe-Ni alloys leads to a broadening of Mössbauer absorption lines. On the …

Cation Distribution And Magnetisation Study Of Nd^{+3} Substituted Zn-Mg Ferrites, B. P. Ladgaonkar, P. N. Vasambekar, A. S. Vaingankar

Turkish Journal of Physics

Polycrystalline ferrites Zn_{x}Mg_{1-x}Fe_{2-y}Nd_{y}O_{4} (x = 0.00, 0.20, 0.40, 0.80 and 1.00; y = 0.00, 0.05 and 0.10) were prepared by standard ceramic method. Thecompositions,oncharacterisation by X-ray diffraction, shows formation of single phase cubic spinels. Magnetic measurement of these composition shows increase in magnetic moment n_{\beta} with Zn^{2+} concentration up to x = 0.4 and decreases thereafter. This is attributed to the existence of locallised canted spin. The compositions for x = 0.8 and 1.0 shows paramagnetic behaviour at and above room temperature. The trivalent substitution of Nd^{3+} ion causes reduction in the magnetic moment. The cation distribution of the sytem …

Effect Of Carrier Concentration Dependant Mobility On The Performance Of High Electron Mobility Transistors, Mustafa Erol

Turkish Journal of Physics

The influence of the sheet carrier concentration dependence on mobility on the performance of High Electron Mobility Transistor (HEMT) structures is theoretically modeled. The model basically takes into account both the drift and diffusion part of the overall drain current. The normalised drain current and normalised transconductance are found to be greatly affected by the carrier concentration dependant mobility.

Factors Affecting Radon Concentration In Houses, Abdel-Latif Al-Sharif, Y. S. Abdelrahman

Turkish Journal of Physics

The dangers to the human health upon exposure to radon and its daughter products is the main motivation behind the vast number of studies performed to find the concentration of radon in our living environment, including our houses. The presence of radon and its daughter products in houses are due to various sources including building materials and the soil under the houses. Many factors affect radon concentration in our houses, the elevation above ground level,ventilation, building materials and room usage being among these factors. In our paper, we discuss the effect of elevation above ground level, room usage and ventilation …

Viscous Dissipation Of Magnetosonic Waves In Solar Corona, Belinda Kalomeni, D. Özlem Hürkal, E. Rennan Pekünlü, Kadri̇ Yakut

Turkish Journal of Physics

Wave propagation and dissipation of magnetosonic waves are considered in an inhomogenous viscous coronal plasma permeated by a spatially varying magnetic field. In the linear magnetohydrodynamic approximation the dispersion relation yields two wave modes, fast and slow respectively. Depending on the physical parameters of the medium the damping length scales of the modes show varying behaviours. Damping length scales of the modes show sudden decrease at relevant heights. These drops may be due to phase mixing and resonance absorption. Wave flux density of the magnetosonic waves turns out to be of the order of 10^6 erg cm^{-2} s^{-1}. This is …

Exciton Investigations And The Urbach Tails Of Gd Doped And Undoped Gase, Beki̇r Gürbulak

Turkish Journal of Physics

Absorption measurements were carried out in GaSe and GaSe:Gd samples in temperature range 10-320 K in steps 10 K. The first and the second (n=1 and n=2) excitonic levels were marked. The first exciton energies for n=1 were calculated as 2.118, 2.008 eV in GaSe, and 2.125, 2.006 eV in GaSe:Gd at 10, 320 K and respectively. The second exciton energies for n=2 were calculated as 2.140, 2.125 eV in GaSe at 10, 80 K and 2.141, 2.120 eV in GaSe:Gd at 10, 120 K and respectively. Binding energies of GaSe and GaSe:Gd were calculated as (29.46\pm 1 and 21.33\pm …

The Theoretical Analysis Of The Second Order Coherence G^{(2)}(\Tau) And Power Stabilization Of Two-Mode He-Ne Laser, Erol Taşal, M. Selami̇ Kiliçkaya

Turkish Journal of Physics

In this study, second-order coherence and its frequency-dependent characteristics and the photon statistical properties of the two-mode He-Ne laser field are investigated.

A Theoretical Analysis Of Transverse Mode Control In Waveguide Gas Lasers, Erol Taşal, M. Selami̇ Kiliçkaya

Turkish Journal of Physics

Theoretical of multiple transverse mode laser oscillation involving spatially varying gain and loss are investigated. The effect of gain and loss distribution on mode competition is analyzed. A theoretical analysis of laser transverse mode competition is investigated from the perspective of the spetial overlap of modes with a transverse gain-loss distribution. The dominant mode of laser oscillation is the mode that is stable under small perturbations.

Impurity Conductivity In Semiconductors Resulting From Radiant Excitation, Vakhab T. Toulanov, Aziza Sh. Davletova, Lesbek T. Tashimov, Kamila A. Ortaeva

Turkish Journal of Physics

This paper deals with the derivation of common formulae for induced impurity photosensibility with an arbitrary set of energy levels in the semiconductor gap. We give the expression for the real recombinational situation with two types of impurity levels as well. The basic properties and certain common peculiarities concerning induced photoconductivity in semiconductors are under consideration.

Electrical Characterization Of Gate And Gate:Cu Semiconductor Compounds, Hüsnü Sali̇h Güder, Bahatti̇n Abay, Hasan Efeoğlu, Cevdet Coşkun, Şaki̇r Aydoğan, Yahya Kemal Yoğurtçu

Turkish Journal of Physics

Electrical properties of GaTe and GaTe:Cu binary compound semiconductors were investigated by Hall effect and resistivity measurements in the 77-320 K temperature range. Donor and acceptor densities, compensation ratios, acceptor ionization energies, valence band effective mass of holes and effective density of states in valence band were determined for the undoped and Cu doped samples using the single donor-single acceptor analysis of the hole concentration. Temperature coefficient of the hole mobility was determined and compared with related theories.

Electron Impact Double Ionization Of Helium From [E, (3-1)E] Experiments}, Mevlut Dogan

Turkish Journal of Physics

Electron impact double ionization of helium has been observed in an [e,(3-1)e] experiment at an incident electron energy of 200 eV. 110 eV scattered and 10 eV ejected electrons are observed in coincidence without detection of the second ejected electron (1 eV). Present and previous observations are discussed.

Urbach-Martienssen's Tail In Layered Ternary Semiconductor Tlgas_{2}, Bahatti̇n Abay, Hüsnü Sali̇h Güder, Hasan Efeoğlu, Yahya Kemal Yoğurtçu

Turkish Journal of Physics

Dependence of the absorption coefficient on the photon energy and temperature near the fundamental absorption edge was measured for layered single crystal TlGaS_{2}. The exponentially increasing absorption tail was explained as an Urbach-Martienssen's (U-M's) tail for TlGaS_{2} samples in the 10-340 K temperature range. The characteristic Urbach's parameters such as steepness parameter [\sigma (T)] and Urbach's energy [(E_{u} = k_{B} T / \sigma )] were determined. Analyzing the temperature dependence of these parameters based on the general models, which takes into account the possible role of several different types of disorder, we conclude that the absorption process in the fundamental …

Mathematical Models Of Quiescent Solar Prominences, Iain Mckaig

Mathematics & Statistics Theses & Dissertations

Magnetic fields in the solar atmosphere suspend and insulate dense regions of cool plasma known as prominences. The convection zone may be the mechanism that both generates and expels this magnetic flux through the photosphere in order to make these formations possible. The connection is examined here by modeling the convection zone as both one-dimensional, then more realistically, two-dimensional.

First a Dirichlet problem on a semi-infinite strip is solved using conformal mapping and the method of images. The base of the strip represents the photosphere where a current distribution can be given as a boundary condition, and the strip extends …