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Top quarks at the Tevatron: Measurements of the top quark production and decay with the D0 experiment

Description: This thesis presents two measurements of the to pquark using 230 pb{sup -1} of data recorded with the D0 detector at the Tevatron accelerator. The first measurement determines the top pair production cross section at {radical}s = 1.96 TeV in proton-antiproton collisions. In the standard model of particle physics the top quark decays almost exclusively into a W boson and a b quark. Candidate events are selected by requiring that at least one jet in the event is tagged with the secondary vertex algorithm.
Date: April 1, 2006
Creator: Strandberg, Jonas & U., /Stockholm

High-Contrast Imaging using Adaptive Optics for Extrasolar Planet Detection

Description: Direct imaging of extrasolar planets is an important, but challenging, next step in planetary science. Most planets identified to date have been detected indirectly--not by emitted or reflected light but through the effect of the planet on the parent star. For example, radial velocity techniques measure the doppler shift in the spectrum of the star produced by the presence of a planet. Indirect techniques only probe about 15% of the orbital parameter space of our solar system. Direct methods would probe new parameter space, and the detected light can be analyzed spectroscopically, providing new information about detected planets. High contrast adaptive optics systems, also known as Extreme Adaptive Optics (ExAO), will require contrasts of between 10{sup -6} and 10{sup -7} at angles of 4-24 {lambda}/D on an 8-m class telescope to image young Jupiter-like planets still warm with the heat of formation. Contrast is defined as the intensity ratio of the dark wings of the image, where a planet might be, to the bright core of the star. Such instruments will be technically challenging, requiring high order adaptive optics with > 2000 actuators and improved diffraction suppression. Contrast is ultimately limited by residual static wavefront errors, so an extrasolar planet imager will require wavefront control with an accuracy of better than 1 nm rms within the low- to mid-spatial frequency range. Laboratory demonstrations are critical to instrument development. The ExAO testbed at the Laboratory for Adaptive Optics was designed with low wavefront error and precision optical metrology, which is used to explore contrast limits and develop the technology needed for an extrasolar planet imager. A state-of-the-art, 1024-actuator micro-electrical-mechanical-systems (MEMS) deformable mirror was installed and characterized to provide active wavefront control and test this novel technology. I present 6.5 x 10{sup -8} contrast measurements with a prolate shaped pupil and flat ...
Date: August 18, 2006
Creator: Evans, J W

Structure, ionic Conductivity and mobile Carrier Density in Fast Ionic Conducting Chalcogenide Glasses

Description: This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M{sub 2}S + (0.1 Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2}) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2} was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M{sub 2}S + (0.1Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2}) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na{sub 2}S + ...
Date: December 12, 2006
Creator: Yao, Wenlong

Genotyping and Bioforensics of Ricinus communis

Description: The castor bean plant (Ricinus communis) is a member of the family Euphorbiaceae. In spite of its common name, the castor plant is not a true bean (i.e., leguminous plants belonging to the family, Fabaceae). Ricinus communis is native to tropical Africa, but because the plant was recognized for its production of oil with many desirable properties, it has been introduced and cultivated in warm temperate regions throughout the world (Armstrong 1999 and Brown 2005). Castor bean plants have also been valued by gardeners as an ornamental plant and, historically, as a natural rodenticide. Today, escaped plants grow like weeds throughout much of the southwestern United States, and castor seeds are even widely available to the public for order through the Internet. In this study, multiple loci of chloroplast noncoding sequence data and a few nuclear noncoding regions were examined to identify DNA polymorphisms present among representatives from a geographically diverse panel of Ricinus communis cultivated varieties. The primary objectives for this research were (1) to successfully cultivate castor plants and extract sufficient yields of high quality DNA from an assortment of castor cultivated varieties, (2) to use PCR and sequencing to screen available universal oligos against a small panel of castor cultivars, (3) to identify DNA polymorphisms within the amplified regions, and (4) to evaluate these DNA polymorphisms as appropriate candidates for assay development (see Figure 1). Additional goals were to design, test and optimize assays targeting any DNA polymorphisms that were discovered and to rapidly screen many castor cultivars to determine the amount of diversity present at that particular locus. Ultimately, the goal of this study was to construct a phylogeographic tree representing the genetic relationships present among Ricinus communis cultivars from diverse geographic regions. These research objectives were designed to test the hypothesis that cultivated varieties of ...
Date: November 20, 2006
Creator: Hinckley, A C

Time-varying Reeb Graphs: A Topological Framework Supporting the Analysis of Continuous Time-varying Data

Description: I present time-varying Reeb graphs as a topological framework to support the analysis of continuous time-varying data. Such data is captured in many studies, including computational fluid dynamics, oceanography, medical imaging, and climate modeling, by measuring physical processes over time, or by modeling and simulating them on a computer. Analysis tools are applied to these data sets by scientists and engineers who seek to understand the underlying physical processes. A popular tool for analyzing scientific datasets is level sets, which are the points in space with a fixed data value s. Displaying level sets allows the user to study their geometry, their topological features such as connected components, handles, and voids, and to study the evolution of these features for varying s. For static data, the Reeb graph encodes the evolution of topological features and compactly represents topological information of all level sets. The Reeb graph essentially contracts each level set component to a point. It can be computed efficiently, and it has several uses: as a succinct summary of the data, as an interface to select meaningful level sets, as a data structure to accelerate level set extraction, and as a guide to remove noise. I extend these uses of Reeb graphs to time-varying data. I characterize the changes to Reeb graphs over time, and develop an algorithm that can maintain a Reeb graph data structure by tracking these changes over time. I store this sequence of Reeb graphs compactly, and call it a time-varying Reeb graph. I augment the time-varying Reeb graph with information that records the topology of level sets of all level values at all times, that maintains the correspondence of level set components over time, and that accelerates the extraction of level sets for a chosen level value and time. Scientific data sampled in space-time ...
Date: November 28, 2006
Creator: Mascarenhas, A

Study of Bs mixing at the CDFII experiment with a newly developed opposite side b-flavour tagging algorithm using kaons

Description: This thesis describes the development, calibration and performance evaluation of an Opposite-side b flavor tagger using K mesons at a p{bar p} hadron collider. In particular, this work is performed using data collected by the Collider Detector at Fermilab (CDF) during the Run II of the Tevatron hadron collider running at {radical}s = 1.96 TeV. b flavor tagging consists of the determination of the flavor of the b quark contained within a hadron. This information is vital to perform any time-dependent measurement involving flavor asymmetries in b hadron decays and flavor oscillations, where it is necessary to know whether a b or {bar b} was contained in a hadron when it was produced. Although at a hadron collider the biggest challenge is probably to perform an effective selection of interesting events in real time and with the best signal-to-background ratio, the statistical significance of any time-dependent measurement is proportional to the effectiveness with which the selected data sample is tagged.
Date: October 1, 2006
Creator: Salamanna, Giuseppe & /INFN, Rome

Search for anomalous production of events with a high energy lepton and photon at the Tevatron

Description: We present results of a search for the anomalous production of events containing a high-transverse momentum charged lepton ({ell}, either e or {mu}) and photon ({gamma}), accompanied by missing transverse energy (E{sub T}), and/or additional leptons and photons, and jets (X). We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305 pb{sup -1}, a p{bar p} collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 {ell}{gamma}E{sub T} events versus a standard model expectation of 37.3 {+-} 5.4 events. The level of excess observed in Run I, 16 events with an expectation of 7.6 {+-} 0.7 events (corresponding to a 2.7 {sigma} effect), is not supported by the new data. In the signature of {ell}{ell}{gamma} + X we observe 31 events versus an expectation of 23.0 {+-} 2.7 events. In this sample we find no events with an extra photon or E{sub T} and so find no events like the one ee{gamma}{gamma} E{sub T} event observed in Run I.
Date: January 1, 2006
Creator: Loginov, Andrey Borisovich & /Moscow, ITEP

Search for new physics in electron-tau final states in proton - antiproton collisions at 1.96 TeV

Description: During the last decades, particle physicists have studied the tiniest building blocks of matter--the quarks and the leptons--and the forces between them in great detail. From these experiments, a theoretical framework has been built that describes the observed results with high precision. The achievement of this theory, which is referred to as the Standard Model of elementary particle physics, was the elaboration of a unified description of the strong, weak and electromagnetic forces in the framework of quantum gauge-field theories. Moreover, the Standard Model combines the weak and electromagnetic forces in a single electroweak gauge theory. The fourth force which is realized in nature, gravity, is too weak to be observable in laboratory experiments carried out in high-energy particle physics and is not part of the Standard Model. Although the Standard Model has proven highly successful in correlating a huge amount of experimental results, a key ingredient is as yet untested: the origin of electroweak symmetry breaking. Currently, the only viable ansatz that is compatible with observation is the Higgs mechanism. It predicts the existence of a scalar particle, called the Higgs boson, and the couplings to the fundamental Standard Model particles, however not its mass. An upper limit on the mass of the Higgs boson of {approx} 1 TeV can be inferred from unitarity arguments. One of the key tasks of particle physics in the next years will be to verify the existence of this particle. The introduction of an elementary scalar particle in a quantum field theory is highly problematic. The Higgs boson mass is subject to large quantum corrections, which makes it difficult to understand how its mass can be less than a TeV as required by theory. In addition, the Standard Model does not provide an answer to fundamental questions like the values of free parameters ...
Date: April 1, 2006
Creator: Noeding, Carsten & U., /Freiburg

Search for 3rd Generation Vector Leptoquarks in the Di-tau Di-jet Channel in Proton Antiproton Collisions at square root s = 1.96 TeV

Description: We search for third generation vector leptoquarks (V LQ3) produced in colliding p{bar p} beams operating at {radical}s = 1.96 TeV at the CDF experiment in Run II of the Fermilab Tevatron. We use 322 pb{sup -1} of data to search for the V LQ3 signal in the di-tau plus di-jet channel. For the first time, the full matrix element is used in the Monte Carlo simulation of this signal. With no events observed in the signal region, we set a 95% C.L. upper limit on the V LQ3 pair production cross section of {sigma} < 344fb, assuming Yang-Mills couplings and Br(V LQ3 {yields} b{tau}) = 1, and a lower limit on the V LQ3 mass of m{sub V LQ3} > 317 GeV=c{sup 2}. If theoretical uncertainties on the cross section are applied in the least favorable manner the results are {sigma} < 360fb and m{sub V LQ3} > 294 GeV=c{sup 2}. The Minimal coupling V LQ3 result is an upper limit on the cross section of {sigma} < 493fb ({sigma} < 610fb) and the lower limit on the mass is m{sub V LQ3} > 251 GeV=c{sup 2} (m{sub V LQ3} > 223 GeV=c{sup 2}) for the nominal (1{sigma} varied) theoretical expectation.
Date: December 1, 2006
Creator: Forrester, Stanley Scott & /UC, Davis

Search for techniparticles at D0 Run II

Description: Technicolor theory (TC) accomplishes the necessary electroweak symmetry breaking responsible for the mass of the elementary particles. TC postulates the existence of a new SU(N{sub TC}) gauge theory. Like QCD the exchange of gauge bosons causes the existence of a non-vanishing chiral condensate which dynamically breaks the SU(N{sub TC}){sub L} x SU(N{sub TC}){sub R} symmetry. This gives rise to N{sub TC}{sup 2}-1 Nambu-Goldstone Bosons. Three of these Goldstone Bosons become the longitudinal components of the W{sup {+-}} and Z which therefore acquire mass; the remaining ones are new particles (technihadrons) that can be produced at the high energy colliders and detected. The Technicolor Straw Man Model (TCSM) is a version of the dynamical symmetry breaking with a large number of technifermions and a relative low value of their masses. One of the processes predicted by the TCSM is q{bar q} {yields} V{sub T} {yields} W{pi}{sub T}, where V{sub T} is the Technicolor equivalent of the QCD vector meson and {pi}{sub T} is the equivalent of the pion. W is the electroweak gauge boson of the Standard Model. This dissertation describes the search for W{pi}{sub T} with the D0 detector, a multi-purpose particle detector located at one of the collision points of the Tevatron accelerator situated in Batavia, IL. The final state considered for this thesis is a W boson that decays to electron and neutrino plus a {pi}{sub T} that decays into b{bar c} or b{bar b}, depending on the charge of the initial technivector meson produced. In the D0 detector this process will appear as a narrow cluster of energy deposits in the electromagnetic calorimeter with an associated track reconstructed in the tracking detector. The undetected neutrino from the decay of the W boson will be seen as missing momentum. The fragmentation of the quarks from the decay of ...
Date: January 1, 2006
Creator: Feligioni, Lorenzo & U., /Boston

An indirect measurement of the width of the w boson at the D0 experiment

Description: This thesis presents an indirect measurement of the width of the W boson using data collected at the D0 experiment, a multipurpose particle detector utilizing the Fermilab Tevatron. The W width was determined from the ratio of W {yields} {mu}{nu} to Z {yields} {mu}{sup +}{mu}{sup -} cross sections to be {Gamma}{sub W} = 2168 {+-} 22(stat) {+-} 62(syst){sub -16}{sup +24}(pdf) {+-} 4(other) MeV, in good agreement with the Standard Model prediction and other experimental measurements. In addition there is a description of how work made towards this measurement has been used to improve the parameterized detector simulation, a vital tool in the obtention of physics results from signals observed in the detector, and in estimating the uncertainty due to choice of PDF, which is of interest for all measurements made at hadron colliders.
Date: August 1, 2006
Creator: Telford, Paul & U., /Manchester

Inclusive high-p(T) b anti-b cross section measurement at s**(1/2) = 1.96-TeV

Description: The Run II physics program at the Tevatron started in the spring of 2001 with protons and antiprotons colliding at an energy of {radical}s = 1.96 TeV, and is continuing with about 1.2 fb{sup -1} of data currently collected by the CDF and D0 experiments. A measurement of the b-jet cross section as function of jet transverse momentum p{perpendicular} has been performed using 312 pb{sup -1} of D0 data. The results for this measurement were obtained and are presented herein. A neural network algorithm was used to identify b jets.
Date: August 1, 2006
Creator: Galyaev, Eugene N. & U., /Notre Dame

Lifetime difference in the Bs0 system from untagged Bs0 ---> J/psi phi decay at s**(1/2) = 1.96 TeV at D0 detector

Description: In this dissertation, they present a study of the untagged decay of B{sub s}{sup 0} {yields} J/{psi}{phi}, the final state of which is a superposition of the CP-even and CP-odd states. Within the framework of the standard model (SM), to a good approximation, the two CP eigenstates of the (B{sub s}{sup 0}, {bar B}{sub s}{sup 0}) system are equivalent to mass eigenstates. The data collected by the D0 detector between June 2002 to August 2004 (an integrated luminosity of approximately 450 pb{sup -1}) has been used for the analysis presented in this thesis. From a simultaneous fit to the B{sub s}{sup 0} candidate mass, lifetime, and the angular distribution of the decay products, they obtain the CP-odd fraction in the final state at production time to be 0.16 {+-} 0.10(stat) {+-} 0.02(syst). The average lifetime of the (B{sub s}{sup 0}, {bar B}{sub s}{sup 0}) system is measured to be 1.39{sub -0.16}{sup +0.13}(stat){sub -0.02}{sup +0.01}(syst) ps, with the relative width difference between the heavy and light mass eigenstates, {Delta}{Gamma}/{bar {Gamma}} = ({Gamma}{sup L}/{Gamma}{sup H})/{bar {Gamma}} = 0.24{sub -0.38}{sup +0.28}(stat){sub -0.04}{sup +0.03}(syst). With the additional constraint from the world average of the B{sub s}{sup 0} lifetime measurements using semileptonic decays, they find average lifetime of the (B{sub s},{sup 0}, {bar B}{sub s}{sup 0}) system 1.39 {+-} 0.06 ps with {Delta}{Gamma}/{bar {Gamma}} = 0.25{sub -0.15}{sup +0.14}. They have also done B{sup 0} lifetime measurement for its analogous decay mode to J/{psi}K*. With this measurement they get B{sup 0} lifetime 1.530 {+-} 0.043(stat) {+-} 0.023(syst) ps. Using above results, they get 0.91 {+-} 0.09(stat) {+-} 0.003(syst), for the ratio of the B{sub s}{sup 0} and B{sup 0} lifetimes ({bar {Gamma}}(B{sub s}{sup 0})/{Gamma}(B{sup 0})). These measurements are consistent with the predictions of SM within the measurement uncertainty.
Date: November 1, 2006
Creator: Chandra, Avdhesh & Inst., /Tata

A combined muon-neutrino and electron-neutrino oscillation search at MiniBooNE

Description: MiniBooNE seeks to corroborate or refute the unconfirmed oscillation result from the LSND experiment. If correct, the result implies that a new kind of massive neutrino, with no weak interactions, participates in neutrino oscillations. MiniBooNE searches for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations with the Fermi National Accelerator Laboratory 8 GeV beam line, which produces a {nu}{sub {mu}} beam with an average energy of {approx} 0.8 GeV and an intrinsic {nu}{sub e} content of 0.4%. The neutrino detector is a 6.1 m radius sphere filled with CH{sub 2}, viewed by 1540 photo-multiplier tubes, and located 541 m downstream from the source. This work focuses on the estimation of systematic errors associated with the neutrino flux and neutrino interaction cross section predictions, and in particular, on constraining these uncertainties using in-situ MiniBooNE {nu}{sub {mu}} charged current quasielastic (CCQE) scattering data. A data set with {approx} 100,000 events is identified, with 91% CCQE purity. This data set is used to measure several parameters of the CCQE cross section: the axial mass, the Fermi momentum, the binding energy, and the functional dependence of the axial form factor on four-momentum transfer squared. Constraints on the {nu}{sub {mu}} and {nu}{sub e} fluxes are derived using the {nu}{sub {mu}} CCQE data set. A Monte Carlo study of a combined {nu}{sub {mu}} disappearance and {nu}{sub e} appearance oscillation fit is presented, which improves the {nu}{sub {mu}} {yields} {nu}{sub e} oscillation sensitivity of MiniBooNE with respect to a {nu}{sub e} appearance-only fit by 1.2-1.5{sigma}, depending on the value of {Delta}m{sup 2}.
Date: July 1, 2006
Creator: Monroe, Jocelyn R. & U., /Columbia

Developing New Nanoprobes from Semiconductor Nanocrystals

Description: In recent years, semiconductor nanocrystal quantum dots havegarnered the spotlight as an important new class of biological labelingtool. Withoptical properties superior to conventional organicfluorophores from many aspects, such as high photostability andmultiplexing capability, quantum dots have been applied in a variety ofadvanced imaging applications. This dissertation research goes along withlarge amount of research efforts in this field, while focusing on thedesign and development of new nanoprobes from semiconductor nanocrystalsthat are aimed for useful imaging or sensing applications not possiblewith quantum dots alone. Specifically speaking, two strategies have beenapplied. In one, we have taken advantage of the increasing capability ofmanipulating the shape of semiconductor nanocrystals by developingsemiconductor quantum rods as fluorescent biological labels. In theother, we have assembled quantum dots and gold nanocrystals into discretenanostructures using DNA. The background information and synthesis,surface manipulation, property characterization and applications of thesenew nanoprobes in a few biological experiments are detailed in thedissertation.
Date: May 29, 2006
Creator: Fu, Aihua

Understanding How Femtosecond Laser Waveguide Fabrication in Glasses Works

Description: In order to understand the physical processes associated with fs-laser waveguide writing in glass, the effects of the laser repetition rate, the material composition and feature size were studied. The resulting material changes were observed by collecting Raman and fluorescence spectra with a confocal microscope. The guiding behavior of the waveguides was evaluated by measuring near field laser coupling profiles in combination with white light microscopy. Waveguides and Bragg gratings were fabricated in fused silica using pulse repetition rates from 1 kHz to 1 MHz and a wide range of scan speeds and pulse energies. Two types of fluorescence were detected in fused silica, depending on the fabrication conditions. Fluorescence from self trapped exciton (E{prime}{sub {delta}}) defects, centered at 550 nm, were dominant for conditions with low total doses, such as using a 1 kHz laser with a scan speed of 20 {micro}m/s and pulse energies less than 1 {micro}J. For higher doses a broad fluorescence band, centered at 650 nm, associated with non-bridging oxygen hole center (NBOHC) defects was observed. Far fewer NBOHC defects were formed with the 1 MHz laser than with the kHz lasers possibly due to annealing of the defects during writing. We also observed an increase in the intensity of the 605 cm{sup -1} Raman peak relative to the total Raman intensity, corresponding to an increase in the concentration of 3-membered rings for all writing conditions. The magnitude of this increase in waveguides fabricated with a 1 MHz laser was nearly twice that of waveguides fabricated with a 1 kHz laser. Additional waveguides were fabricated in soda lime silicate glasses to assess the effects of changing the glass composition. These waveguides formed around, not inside the exposed regions. This is distinctly different from fused silica in which the waveguides are inside the exposed regions. A ...
Date: May 11, 2006
Creator: Reichman, W J

Under-sampling in a Multiple-Channel Laser Vibrometry System

Description: Laser vibrometry is a technique used to detect vibrations on objects using the interference of coherent light with itself. Most vibrometry systems process only one target location at a time, but processing multiple locations simultaneously provides improved detection capabilities. Traditional laser vibrometry systems employ oversampling to sample the incoming modulated-light signal, however as the number of channels increases in these systems, certain issues arise such a higher computational cost, excessive heat, increased power requirements, and increased component cost. This thesis describes a novel approach to laser vibrometry that utilizes undersampling to control the undesirable issues associated with over-sampled systems. Undersampling allows for significantly less samples to represent the modulated-light signals, which offers several advantages in the overall system design. These advantages include an improvement in thermal efficiency, lower processing requirements, and a higher immunity to the relative intensity noise inherent in laser vibrometry applications. A unique feature of this implementation is the use of a parallel architecture to increase the overall system throughput. This parallelism is realized using a hierarchical multi-channel architecture based on off-the-shelf programmable logic devices (PLDs).
Date: August 15, 2006
Creator: Corey, J

Search for large extra dimensions in the exclusive photon + missing energy channel in p anti-p collisions

Description: A search was conducted for evidence of large extra dimensions (LED) at Fermi National Accelerator Laboratory's Tevatron using the D0 detector. The Tevatron is a p{bar p} collider at a center of mass energy of 1.96 TeV. Events with particles escaping into extra dimensions will have large missing energy. The search was carried out using data from a total luminosity of 197 {+-} 13 pb{sup -1} with an observable high transverse momentum photon and a large transverse missing energy. The 70 observed events are consistent with photons produced by standard known reactions plus other background processes produced by cosmic muons. The mass limits on the fundamental mass scale at 95% confidence level for large extra dimensions of 2, 4, 6 and 8 are 500 GeV, 581 GeV, 630 GeV, and 668 GeV respectively.
Date: April 1, 2006
Creator: Lazoflores, Jose A. & U., /Florida State

Some aspects of hadron-hadron collisions in high energy interactions (Bs mixing oscillations in semileptonic decay at D0 experiment)

Description: In this thesis, we report the study on one such particle called the B{sub s}{sup 0} meson made up of a bottom and a strange quark. B{sub s}{sup 0} mesons are currently produced in a great numbers only at the Tevatron and we report a study done to measure the mixing parameter {Delta}m{sub s} between the B{sub s}{sup 0} meson and its anti-particle {bar B}{sub s}{sup 0}. Mixing is the ability of a very few neutral mesons to change from their particle to their antiparticle and vice versa. Until recently there existed only a lower limit on this measurement, here we report an upper bound and a most probable value for the mixing parameter. In the following chapter, we discuss the theoretical motivation behind this study. The measurement technique and the different factors that effect the measurement are also given. In Chapter 3, we provide an overview of the experimental setup needed to perform the study. In Chapter 4, we present a new initial state flavor tagging algorithm using electrons and measurement of the B{sub d}{sup 0} mixing parameter {Delta}m{sub d} with the new technique. Details of the combined initial state tagging used in the B{sub s}{sup 0} mixing study are also given. A detailed description of the B{sub s}{sup 0} mixing analysis and the results are covered in Chapter 5. And finally the results from all the three channels and a bound on the mixing parameter are presented in Chapter 6.
Date: September 1, 2006
Creator: Naimuddin, Md. & U., /Delhi

Superconducting High Resolution Fast-Neutron Spectrometers

Description: Superconducting high resolution fast-neutron calorimetric spectrometers based on {sup 6}LiF and TiB{sub 2} absorbers have been developed. These novel cryogenic spectrometers measure the temperature rise produced in exothermal (n, {alpha}) reactions with fast neutrons in {sup 6}Li and {sup 10}B-loaded materials with heat capacity C operating at temperatures T close to 0.1 K. Temperature variations on the order of 0.5 mK are measured with a Mo/Cu thin film multilayer operated in the transition region between its superconducting and its normal state. The advantage of calorimetry for high resolution spectroscopy is due to the small phonon excitation energies k{sub B}T on the order of {mu}eV that serve as signal carriers, resulting in an energy resolution {Delta}E {approx} (k{sub B}T{sup 2}C){sup 1/2}, which can be well below 10 keV. An energy resolution of 5.5 keV has been obtained with a Mo/Cu superconducting sensor and a TiB{sub 2} absorber using thermal neutrons from a {sup 252}Cf neutron source. This resolution is sufficient to observe the effect of recoil nuclei broadening in neutron spectra, which has been related to the lifetime of the first excited state in {sup 7}Li. Fast-neutron spectra obtained with a {sup 6}Li-enriched LiF absorber show an energy resolution of 16 keV FWHM, and a response in agreement with the {sup 6}Li(n, {alpha}){sup 3}H reaction cross section and Monte Carlo simulations for energies up to several MeV. The energy resolution of order of a few keV makes this novel instrument applicable to fast-neutron transmission spectroscopy based on the unique elemental signature provided by the neutron absorption and scattering resonances. The optimization of the energy resolution based on analytical and numerical models of the detector response is discussed in the context of these applications.
Date: May 25, 2006
Creator: Hau, I D

Fast Ignition Experimental and Theoretical Studies

Description: We are becoming dependent on energy more today than we were a century ago, and with increasing world population and booming economies, sooner or later our energy sources will be exhausted. Moreover, our economy and welfare strongly depends on foreign oil and in the shadow of political uncertainties, there is an urgent need for a reliable, safe, and cheap energy source. Thermonuclear fusion, if achieved, is that source of energy which not only will satisfy our demand for today but also for centuries to come. Today, there are two major approaches to achieve fusion: magnetic confinement fusion (MFE) and inertial confinement fusion (ICF). This dissertation explores the inertial confinement fusion using the fast ignition concept. Unlike the conventional approach where the same laser is used for compression and ignition, in fast ignition separate laser beams are used. This dissertation addresses three very important topics to fast ignition inertial confinement fusion. These are laser-to-electron coupling efficiency, laser-generated electron beam transport, and the associated isochoric heating. First, an integrated fast ignition experiment is carried out with 0.9 kJ of energy in the compression beam and 70 J in the ignition beam. Measurements of absolute K{sub {alpha}} yield from the imploded core revealed that about 17% of the laser energy is coupled to the suprathermal electrons. Modeling of the transport of these electrons and the associated isochoric heating, with the previously determined laser-to-electron conversion efficiency, showed a maximum target temperature of 166 eV at the front where the electron flux is higher and the density is lower. The contribution of the potential, induced by charge separation, in opposing the motion of the electrons was moderate. Second, temperature sensitivity of Cu K{sub {alpha}} imaging efficiency using a spherical Bragg reflecting crystal is investigated. It was found that due to the shifting and broadening of ...
Date: October 20, 2006
Creator: Akli, K

Resolution Improvement and Pattern Generator Development for theMaskless Micro-Ion-Beam Reduction Lithography System

Description: The shrinking of IC devices has followed the Moore's Law for over three decades, which states that the density of transistors on integrated circuits will double about every two years. This great achievement is obtained via continuous advance in lithography technology. With the adoption of complicated resolution enhancement technologies, such as the phase shifting mask (PSM), the optical proximity correction (OPC), optical lithography with wavelength of 193 nm has enabled 45 nm printing by immersion method. However, this achievement comes together with the skyrocketing cost of masks, which makes the production of low volume application-specific IC (ASIC) impractical. In order to provide an economical lithography approach for low to medium volume advanced IC fabrication, a maskless ion beam lithography method, called Maskless Micro-ion-beam Reduction Lithography (MMRL), has been developed in the Lawrence Berkeley National Laboratory. The development of the prototype MMRL system has been described by Dr. Vinh Van Ngo in his Ph.D. thesis. But the resolution realized on the prototype MMRL system was far from the design expectation. In order to improve the resolution of the MMRL system, the ion optical system has been investigated. By integrating a field-free limiting aperture into the optical column, reducing the electromagnetic interference and cleaning the RF plasma, the resolution has been improved to around 50 nm. Computational analysis indicates that the MMRL system can be operated with an exposure field size of 0.25 mm and a beam half angle of 1.0 mrad on the wafer plane. Ion-ion interactions have been studied with a two-particle physics model. The results are in excellent agreement with those published by the other research groups. The charge-interaction analysis of MMRL shows that the ion-ion interactions must be reduced in order to obtain a throughput higher than 10 wafers per hour on 300-mm wafers. In addition, two different ...
Date: May 18, 2006
Creator: Jiang, Ximan

High Pressure Scanning Tunneling Microscopy and High PressureX-ray Photoemission Spectroscopy Studies of Adsorbate Structure,Composition and Mobility during Catalytic Reactions on A Model SingleCrystal

Description: Our research focuses on taking advantage of the ability of scanning tunneling microscopy (STM) to operate at high-temperatures and high-pressures while still providing real-time atomic resolution images. We also utilize high-pressure x-ray photoelectron spectroscopy (HPXPS) to monitor systems under identical conditions thus giving us chemical information to compare and contrast with the structural and dynamic data provided by STM.
Date: May 12, 2006
Creator: Montano, M. O.