Measurement of the W Boson Mass with the D0 Run II Detector using the Electron P(T) Spectrum (open access)

Measurement of the W Boson Mass with the D0 Run II Detector using the Electron P(T) Spectrum

This thesis is a description of the measurement of the W boson mass using the D0 Run II detector with 770 pb{sup -1} of p{bar p} collision data. These collisions were produced by the Tevatron at {radical}s = 1.96 TeV between 2002 and 2006. We use a sample of W {yields} e{nu} and Z {yields} ee decays to determine the W boson mass with the transverse momentum distribution of the electron and the transverse mass distribution of the boson. We measure M{sub W} = XXXXX {+-} 37 (stat.) {+-} 26 (sys. theo.) {+-} 51 (sys. exp.) MeV = XXXXX {+-} 68 MeV with the transverse momentum distribution of the electron and M{sub W} = XXXXX {+-} 28 (stat.) {+-} 17 (sys. theo.) {+-} 51 (sys. exp.) MeV = XXXXX {+-} 61 MeV with the transverse mass distribution.
Date: June 1, 2008
Creator: Andeen, Timothy R., Jr.
System: The UNT Digital Library
Study of B_s Mixing at the D-Zero Detector at Fermilab Using the Semi-leptonic Decay B_s -> D_s mu nu X (open access)

Study of B_s Mixing at the D-Zero Detector at Fermilab Using the Semi-leptonic Decay B_s -> D_s mu nu X

B{sub s}{sup 0} mixing studies provide a precision test of Charge-Parity violation in the Standard Model. A measurement of {Delta}m{sub s} constrains elements of the CKM quark rotation matrix [1], providing a probe of Standard Model Charge-Parity violation. This thesis describes a study of B{sub s}{sup 0} mixing in the semileptonic decay B{sub s}{sup 0} {yields} D{sub s}{sup -} {mu}{sup +}{nu}X, where D{sub s}{sup -} {yields} {phi}{pi}{sup -}, using data collected at the D-Zero detector at Fermi National Accelerator in Batavia, Illinois. Approximately 2.8 fb{sup -1} of data collected between April 2002 and August 2007 was used, covering the entirety of the Tevatron's RunIIa (April 2002 to March 2006) and part of RunIIb (March 2006-August 2007). Taggers using both opposite-side and same-side information were used to obtain the flavor information of the B{sub s}{sup 0} meson at production. The charge of the muon in the decay B{sub s}{sup 0} {yields} D{sub s}{sup -}{mu}{sup +}{nu}X was used to determine the flavor of the B{sub s}{sup 0} at decay. The B{sub d}{sup 0} mixing frequency, {Delta}m{sub d}, was measured to verify the analysis procedure. A log-likelihood calculation was performed, and a measurement of {Delta}m{sub s} was obtained. The final result was {Delta}m{sub …
Date: June 1, 2008
Creator: Anzelc, Meghan
System: The UNT Digital Library
Structural Investigations of Surfaces and Orientation-SpecificPhenomena in Nanocrystals and Their Assemblies (open access)

Structural Investigations of Surfaces and Orientation-SpecificPhenomena in Nanocrystals and Their Assemblies

Studies of colloidal nanocrystals and their assemblies are presented. Two of these studies concern the atomic-level structural characterization of the surfaces, interfaces, and interiors present in II-VI semiconductor nanorods. The third study investigates the crystallographic arrangement of cobalt nanocrystals in self-assembled aggregates. Crystallographically-aligned assemblies of colloidal CdSe nanorods are examined with linearly-polarized Se-EXAFS spectroscopy, which probes bonding along different directions in the nanorod. This orientation-specific probe is used, because it is expected that the presence of specific surfaces in a nanorod might cause bond relaxations specific to different crystallographic directions. Se-Se distances are found to be contracted along the long axis of the nanorod, while Cd-Se distances display no angular dependence, which is different from the bulk. Ab-initio density functional theory calculations upon CdSe nanowires indicate that relaxations on the rod surfaces cause these changes. ZnS/CdS-CdSe core-shell nanorods are studied with Se, Zn, Cd, and S X-ray absorption spectroscopy (XAS). It is hypothesized that there are two major factors influencing the core and shell structures of the nanorods: the large surface area-to-volume ratio, and epitaxial strain. The presence of the surface may induce bond rearrangements or relaxations to minimize surface energy; epitaxial strain might cause the core and shell lattices …
Date: June 17, 2006
Creator: Aruguete, Deborah Michiko
System: The UNT Digital Library
Development of Trivalent Ytterbium Doped Fluorapatites for Diode-Pumped Laser Applications (open access)

Development of Trivalent Ytterbium Doped Fluorapatites for Diode-Pumped Laser Applications

One of the major motivators of this work is the Mercury Project, which is a 1 kW scalable diode-pumped solid-state laser system under development at Lawrence Livermore National Laboratory (LLNL). Major goals include 100 J pulses, 10% wallplug efficiency, 10 Hz repetition rate, and a 5 times diffraction limited beam. To achieve these goals the Mercury laser incorporates ytterbium doped Sr{sub 5}(PO{sub 4}){sub 3}F (S-FAP) as the amplifier gain medium. The primary focus of this thesis is a full understanding of the properties of this material which are necessary for proper design and modeling of the system. Ytterbium doped fluorapatites, which were previously investigated at LLNL, were found to be ideal candidate materials for a high power amplifier systems providing high absorption and emission cross sections, long radiative lifetimes, and high efficiency. A family of barium substituted S-FAP crystals were grown in an effort to modify the pump and emission bandwidths for application to broadband diode pumping and short pulse generation. Crystals of Yb{sup 3+}:Sr{sub 5-x}Ba{sub x}(PO{sub 4}){sub 3}F where x < 1 showed homogeneous lines offering 8.4 nm (1.8 times enhancement) of absorption bandwidth and 6.9 nm (1.4 times enhancement) of emission bandwidth. The gain saturation fluence of Yb:S-FAP …
Date: June 21, 2000
Creator: Bayramian, A. J.
System: The UNT Digital Library
Search for the Trilepton Signal of the Minimal Supergravity Model in D0 Run II (open access)

Search for the Trilepton Signal of the Minimal Supergravity Model in D0 Run II

A search for associated chargino neutralino pair production is performed in the trilepton decay channel q{bar q} {yields} {tilde {chi}}{sub 1}{sup {+-}} {tilde {chi}}{sub 2}{sup 0} {yields} {ell}{sup {+-}} {nu} {tilde {chi}}{sub 1}{sup 0} {mu}{sup {+-}} {mu}{sup {-+}} {tilde {chi}}{sub 1}{sup 0}, using data collected with the D0 detector at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. The data sample corresponds to an integrated luminosity of {approx}300 pb{sup -1}. A dedicated event selection is applied to all samples including the data sample and the Monte Carlo simulated samples for the Standard Model background and the Supersymmetry signal. Events with two muons plus an additional isolated track, replacing the requirement of a third charged lepton in the event, are analyzed. Additionally, selected events must have a large amount of missing transverse energy due to the neutrino and the two {tilde {chi}}{sub 1}{sup 0}. After all selection cuts are applied, 2 data events are found, with an expected number of background events of 1.75 {+-} 0.34 (stat.) {+-} 0.46 (syst.). No evidence for Supersymmetry is found and limits on the production cross section times leptonic branching fraction are set. When the presented analysis is considered in combination with …
Date: June 1, 2005
Creator: Binder, Meta
System: The UNT Digital Library
M dwarfs in the Local Milky Way: The Field Low-Mass Stellar Luminosity and Mass Functions (open access)

M dwarfs in the Local Milky Way: The Field Low-Mass Stellar Luminosity and Mass Functions

Modern sky surveys, such as the Sloan Digital Sky Survey (SDSS) and the Two-Micron All Sky Survey, have revolutionized how Astronomy is done. With millions of photometric and spectroscopic observations, global observational properties can be studied with unprecedented statistical significance. Low-mass stars dominate the local Milky Way, with tens of millions observed by SDSS within a few kpc. Thus, they make ideal tracers of the Galactic potential, and the thin and thick disks. In this thesis dissertation, I present my efforts to characterize the local low-mass stellar population, using a collection of observations from the Sloan Digital Sky Survey (SDSS). First, low-mass stellar template spectra were constructed from the co-addition of thousands of SDSS spectroscopic observations. These template spectra were used to quantify the observable changes introduced by chromospheric activity and metallicity. Furthermore, the average ugriz colors were measured as a function of spectral type. Next, the local kinematic structure of the Milky Way was quantified, using a special set of SDSS spectroscopic observations. Combining proper motions and radial velocities (measured using the spectral templates), along with distances, the full UVW space motions of over 7000 low-mass stars along one line of sight were computed. These stars were also separated …
Date: June 1, 2006
Creator: Bochanski, John J., Jr. & /Washington U., Seattle, Astron. Dept.
System: The UNT Digital Library
MRI of Heterogeneous Hydrogenation Reactions Using Parahydrogen Polarization (open access)

MRI of Heterogeneous Hydrogenation Reactions Using Parahydrogen Polarization

The power of magnetic resonance imaging (MRI) is its ability to image the internal structure of optically opaque samples and provide detailed maps of a variety of important parameters, such as density, diffusion, velocity and temperature. However, one of the fundamental limitations of this technique is its inherent low sensitivity. For example, the low signal to noise ratio (SNR) is particularly problematic for imaging gases in porous materials due to the low density of the gas and the large volume occluded by the porous material. This is unfortunate, as many industrially relevant chemical reactions take place at gas-surface interfaces in porous media, such as packed catalyst beds. Because of this severe SNR problem, many techniques have been developed to directly increase the signal strength. These techniques work by manipulating the nuclear spin populations to produce polarized} (i.e., non-equilibrium) states with resulting signal strengths that are orders of magnitude larger than those available at thermal equilibrium. This dissertation is concerned with an extension of a polarization technique based on the properties of parahydrogen. Specifically, I report on the novel use of heterogeneous catalysis to produce parahydrogen induced polarization and applications of this new technique to gas phase MRI and the characterization …
Date: June 25, 2008
Creator: Burt, Scott R & Burt, Scott R.
System: The UNT Digital Library
Studies in High Current Density Ion Sources for Heavy Ion FusionApplications (open access)

Studies in High Current Density Ion Sources for Heavy Ion FusionApplications

This dissertation develops diverse research on small (diameter {approx} few mm), high current density (J {approx} several tens of mA/cm{sup 2}) heavy ion sources. The research has been developed in the context of a programmatic interest within the Heavy Ion Fusion (HIF) Program to explore alternative architectures in the beam injection systems that use the merging of small, bright beams. An ion gun was designed and built for these experiments. Results of average current density yield (<J>) at different operating conditions are presented for K{sup +} and Cs{sup +} contact ionization sources and potassium aluminum silicate sources. Maximum <J> values for a K{sup +} beam of {approx}90 mA/cm{sup 2} were observed in 2.3 {micro}s pulses. Measurements of beam intensity profiles and emittances are included. Measurements of neutral particle desorption are presented at different operating conditions which lead to a better understanding of the underlying atomic diffusion processes that determine the lifetime of the emitter. Estimates of diffusion times consistent with measurements are presented, as well as estimates of maximum repetition rates achievable. Diverse studies performed on the composition and preparation of alkali aluminosilicate ion sources are also presented. In addition, this work includes preliminary work carried out exploring the viability …
Date: June 1, 2002
Creator: Chacon-Golcher, E.
System: The UNT Digital Library
Spin correlation in t{anti t} production from p{anti p} collisions at {radical}s = 1.8 TeV (open access)

Spin correlation in t{anti t} production from p{anti p} collisions at {radical}s = 1.8 TeV

The Standard Model predicts that the lifetime of the top quark is shorter than the typical time scale at which hadronization process occurs, and the spin information at its production is preserved. Spin correlation of the t{anti t} system from p{anti p} collisions at the Tevatron is analyzed using 6 events in the dilepton channels collected using the D0 detector. Spin correlation factor of {kappa} > {minus} 0.25 at 68% CL is obtained from the data.
Date: June 15, 2000
Creator: Choi, Suyong
System: The UNT Digital Library
Search for the Standard Model Higgs boson in the missing energy topology with D0 (open access)

Search for the Standard Model Higgs boson in the missing energy topology with D0

A search for the Standard Model Higgs boson in the missing energy and acoplanar b-jet topology is reported, using an integrated luminosity of 0.93 fb{sup -1} recorded by the D0 detector at the Fermilab Tevatron p{bar p} Collider. The analysis includes signal contributions from p{bar p} {yields} ZH {yields} {nu}{bar {nu}}b{bar b}, as well as from WH production in which the charged lepton from the W boson decay is undetected. Neural networks are used to separate signal from background. In the absence of a signal, limits are set on {sigma}(p{bar p} {yields} VH) x B(H {yields} b{bar b}) at the 95% C.L. of 2.6-2.3 pb, for Higgs boson masses in the range 105-135 GeV, where V = W, Z. The corresponding expected limits range from 2.8 to 2.0 pb. Potential improvements to the analysis with an extended dataset totalling 4 fb{sup -1} are also discussed. Essential maintenance related to the increased luminosity and RunIIb upgrade was carried out on the impact parameter (IP) based b-tagging trigger tool and the effect of the changes on the b-tagger's performance was investigated.
Date: June 1, 2009
Creator: Christoudias, Theodoros
System: The UNT Digital Library
Optimization of the signal selection of exclusively reconstructed decays of B0 and B/s mesons at CDF-II (open access)

Optimization of the signal selection of exclusively reconstructed decays of B0 and B/s mesons at CDF-II

The work presented in this thesis is mainly focused on the application in a {Delta}m{sub s} measurement. Chapter 1 starts with a general theoretical introduction on the unitarity triangle with a focus on the impact of a {Delta}m{sub s} measurement. Chapter 2 then describes the experimental setup, consisting of the Tevatron collider and the CDF II detector, that was used to collect the data. In chapter 3 the concept of parameter estimation using binned and unbinned maximum likelihood fits is laid out. In addition an introduction to the NeuroBayes{reg_sign} neural network package is given. Chapter 4 outlines the analysis steps walking the path from the trigger level selection to fully reconstructed B mesons candidates. In chapter 5 the concepts and formulas that form the ingredients to an unbinned maximum likelihood fit of {Delta}m{sub s} ({Delta}m{sub d}) from a sample of reconstructed B mesons are discussed. Chapter 6 then introduces the novel method of using neural networks to achieve an improved signal selection. First the method is developed, tested and validated using the decay B{sup 0} {yields} D{pi}, D {yields} K{pi}{pi} and then applied to the kinematically very similar decay B{sub s} {yields} D{sub s}{pi}, D{sub s} {yields} {phi}{pi}, {phi} {yields} …
Date: June 1, 2006
Creator: Doerr, Christian
System: The UNT Digital Library
Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214 (open access)

Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

Thermodynamics has been studied systematically for the high temperature cuprate superconductor La{sub 2-x}Sr{sub x}CuO{sub 4-{delta}}, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H {parallel} c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T{sub c}, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T{sub c0} vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La{sub 2-x}Sr{sub x}CuO{sub 4} (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to …
Date: June 25, 2001
Creator: Finnemore, Douglas K.
System: The UNT Digital Library
Combustion in Homogeneous Charge Compression Ignition Engines: Experiments and Detailed Chemical Kinetic Simulations (open access)

Combustion in Homogeneous Charge Compression Ignition Engines: Experiments and Detailed Chemical Kinetic Simulations

Homogeneous charge compression ignition (HCCI) engines are being considered as an alternative to diesel engines. The HCCI concept involves premixing fuel and air prior to induction into the cylinder (as is done in current spark-ignition engine) then igniting the fuel-air mixture through the compression process (as is done in current diesel engines). The combustion occurring in an HCCI engine is fundamentally different from a spark-ignition or Diesel engine in that the heat release occurs as a global autoignition process, as opposed to the turbulent flame propagation or mixing controlled combustion used in current engines. The advantage of this global autoignition is that the temperatures within the cylinder are uniformly low, yielding very low emissions of oxides of nitrogen (NO{sub x}, the chief precursors to photochemical smog). The inherent features of HCCI combustion allows for design of engines with efficiency comparable to, or potentially higher than, diesel engines. While HCCI engines have great potential, several technical barriers exist which currently prevent widespread commercialization of this technology. The most significant challenge is that the combustion timing cannot be controlled by typical in-cylinder means. Means of controlling combustion have been demonstrated, but a robust control methodology that is applicable to the entire range …
Date: June 7, 2002
Creator: Flowers, D L
System: The UNT Digital Library
Measurement of the Relative Fragmentation Fractions of B-bar Hadrons (open access)

Measurement of the Relative Fragmentation Fractions of B-bar Hadrons

This thesis describes the first Run II measurement of b quark fragmentation into {bar B}{sup 0}, B{sup -}, and {bar B}{sub s}{sup 0} mesons and {Lambda}{sub b}{sup 0} baryons using semileptonic B decays. The result is based on 360 pb{sup -1} of data collected with the CDF detector in p{bar p} collisions at {radical}s = 1,960 GeV at the Tevatron Collider at Fermilab. The fragmentation fractions are measured for an effective {bar B} hadron p{sub T} threshold of 7 GeV/c to be f{sub u}/f{sub d} = 1.054 {+-} 0.018(stat){sub -0.045}{sup +0.025}(syst) {+-} 0.058(BR), f{sub s}/(f{sub u} + f{sub d}) = 0.160 {+-} 0.005(stat){sub -0.010}{sup +0.011}(syst){sub -0.034}{sup +0.057}(BR), and f{sub {Lambda}{sub b}}/(f{sub u} + f{sub d}) = 0.281 {+-} 0.012(stat){sub -0.056}{sup +0.058}(syst){sub -0.086}{sup +0.128}(BR). f{sub s}/(f{sub u} + f{sub d}) agrees both with previous CDF measurements and the world averages, dominated by the LEP measurements, with {approx} 1{sigma}. However, f{sub {Lambda}{sub b}}/(f{sub u} + f{sub d}) is approximately twice the value which has been measured at LEP and in CDF Run I and disagrees with the LEP results by approximately 2 {sigma}.
Date: June 1, 2006
Creator: Gibson, Karen Ruth
System: The UNT Digital Library
Extraction of the width of the W boson from a measurement of the ratio of the W and Z cross sections (open access)

Extraction of the width of the W boson from a measurement of the ratio of the W and Z cross sections

This dissertation reports on measurements of inclusive cross sections times branching fractions into electrons for W and Z bosons produced in p{anti p} collisions at {radical}s = 1.8 TeV. From an integrated luminosity of 84.5 pb{sup {minus}1} recorded in 1994--1995 by the D0 detector at the Fermilab Tevatron {Lambda} the cross sections are measured to be {sigma}p{anti p} {r_arrow} W + X {center_dot} B(W {r_arrow} e{nu}) = 2,310 {+-} 10 (stat) {+-} 50 (Syst) {+-} 100 (lum) pb and {sigma}(p{anti p} {r_arrow} Z + X) {center_dot} B(Z {r_arrow} ee) = 221 {+-} 3 (stat) {+-} 4 (Syst) {+-} 10 (lum) pb. The cross section ratio R is determined to be {sigma}(p{anti p} {r_arrow} W + X) {center_dot} B(W {r_arrow} e{nu})/{sigma}(p{bar p} {r_arrow} Z + X) {center_dot} B(Z {r_arrow} ee) = 10.43 {+-} 0.15 (stat) {+-} 0.20 (syst) {+-} 0.10 (NLO){Lambda} and R is used to determine B(W {r_arrow} e{nu}) = 0.1044 {+-} 0.0015 (stat) {+-} 0.0020 (syst) {+-} 0.0017 (theory) {+-} 0.0010 (NLO){Lambda} and {Lambda}{sub W} = 2.169 {+-} 0.031 (stat) {+-} 0.042 (syst) {+-} 0.041 (theory) {+-} 0.022 (NLO) GeV. The latter is used to set a 95% confidence level upper limit on the partial decay width of the …
Date: June 15, 2000
Creator: Gomez, Gervasio
System: The UNT Digital Library
A search for neutral Higgs bosons at high tan beta in multi-jet events from p anti-p collisions at s**(1/2) = 1960-GeV (open access)

A search for neutral Higgs bosons at high tan beta in multi-jet events from p anti-p collisions at s**(1/2) = 1960-GeV

The Higgs mechanism preserves the gauge symmetries of the Standard Model while giving masses to the W, Z bosons. Supersymmetry, which protects the Higgs boson mass scale from quantum corrections, predicts at least 5 Higgs bosons, none of which has been directly observed. This thesis presents a search for neutral Higgs bosons, produced in association with bottom quarks. The production rate is greatly enhanced at large values of the Supersymmetric parameter tan {beta}. High-energy p{bar p} collision data, collected from Run II of the Fermilab Tevatron using the D0 detector, are analyzed. In the absence of a signal, values of tan {beta} > 80-120 are excluded at 95% Confidence Level (C.L.), depending on the (CP-odd) neutral Higgs boson mass (studied from 100 to 150 GeV/c{sup 2}).
Date: June 1, 2004
Creator: Haas, Andrew C. & /Washington U., Seattle
System: The UNT Digital Library
Study of 14O as a Test of the Unitarity of the CKM Matrix and the CVC Hypothesis (open access)

Study of 14O as a Test of the Unitarity of the CKM Matrix and the CVC Hypothesis

Abstract: The study of superallowed beta decay in nuclei, in conjunction with other experiments, provide a test of the unitarity of the quark mixing matrix or CKM matrix. Nonunitarity of the CKM matrix could imply the existence of a fourth generation of quarks, right handed currents in the weak interaction, and/or new exotic fermions. Advances in radioactive beam techniques allow the creation of nearly pure samples of nuclei for beta decay studies. The subject of this thesis is the development of a radioactive beam of 14O and the study of the 14O halflife and branching ratio. The radioactive beam is produced by ionizing 12C14O radioactive gas and then accelerating with an ECR ion source. The 14O nucleus decays via superallowed beta decay with a branching ratio > 99 percent. The low Z of 14O is important for calculating reliable corrections to the beta decay that generally increase in with Z. The > 99 percent branching ratio can be established with modest precision on the complementary branching ratio.When this work began the experimentally determined CKM matrix was nonunitary by 2.5 standard deviations. Recent studies of Kaon, Hyperon, and B meson decays have been used to determine Vus and Vub matrix elements. …
Date: June 1, 2004
Creator: Harke, Jason Timothy
System: The UNT Digital Library
Enhancing the Properties of Carbon and Gold Substrates by Surface Modification (open access)

Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic performance both in conventional liquid chromatographic columns and EMLC columns. Additionally, one may also exploit the creation of aryl films to by electroreduction of arenediazonium salts in the creation of nanostructured materials. The formation of mercaptobenzene film on the surface of a GC electrode provides a linking platform for the chemisorption of gold nanoparticles. After deposition of nanoparticles, the surface chemistry of the gold can be further altered by self-assembled monolayer (SAM) formation via the chemisorption of a second thiol species. Finally, the properties of gold films can be altered such that they display carbon-like behavior through the formation of benzenehexathiol …
Date: June 27, 2002
Creator: Harnisch, Jennifer Anne
System: The UNT Digital Library
Measurement of the calorimetric energy scale in MINOS (open access)

Measurement of the calorimetric energy scale in MINOS

MINOS is a long-baseline neutrino oscillation experiment. A neutrino beam is created at the Fermi National Accelerator Laboratory in Illinois and fired down through the Earth. Measurements of the energy spectra and composition of the neutrino beam are made both at the source using the Near detector and 735 km away at the Soudan Underground Laboratory in Minnesota using the Far detector. By comparing the spectrum and flavour composition of the neutrino beam between the two detectors neutrino oscillations can be observed. Such a comparison depends on the accuracy of the relative calorimetric energy scale. This thesis details a precise measurement of the calorimetric energy scale of the MINOS Far detector and Calibration detector using stopping muons with a new ''track window'' technique. These measurements are used to perform the relative calibration between the two detectors. This calibration has been accomplished to 1.7% in data and to significantly better than 2% in the Monte Carlo simulation, thus achieving the MINOS relative calibration target of 2%. A number of cross-checks have been performed to ensure the robustness of the calorimetric energy scale measurements. At the Calibration detector the test-beam energy between run periods is found to be consistent with the detector …
Date: June 1, 2005
Creator: Hartnell, Jeffrey J.
System: The UNT Digital Library
Hydrogen Storage Properties of Lithium Aluminohydride Modified by Dopants and Mechanochemistry (open access)

Hydrogen Storage Properties of Lithium Aluminohydride Modified by Dopants and Mechanochemistry

Alkali metal aluminohydrides have high potential as solid hydrogen storage materials. They have been known for their irreversible dehydrogenation process below 100 atm until Bogdanovic et al succeeded in the re-hydrogenation of NaAlH{sub 4} below 70 atm. They achieved 4 wt.% H{sub 2} reversible capacity by doping NaAlH{sub 4} with Ti and/or Fe organo-metallic compounds as catalysts. This suggests that other alkali and, possibly alkaline earth metal aluminohydrides can be used for reversible hydrogen storage when modified by proper dopants. In this research, Zr{sub 27}Ti{sub 9}Ni{sub 38}V{sub 5}Mn{sub 16}Cr{sub 5}, LaNi{sub 4.85}Sn{sub 0.15}, Al{sub 3}Ti, and PdCl{sub 2} were combined with LiAlH{sub 4} by ball-milling to study whether or not LiAlH{sub 4} is capable to both absorb and desorb hydrogen near ambient conditions. X-ray powder diffraction, differential thermal analysis, and scanning electron microscopy were employed for sample characterizations. All four compounds worked as catalysts in the dehydrogenation reactions of both LiAlH{sub 4} and Li{sub 3}AlH{sub 6} by inducing the decomposition at lower temperature. However, none of them was applicable as catalyst in the reverse hydrogenation reaction at low to moderate hydrogen pressure.
Date: June 27, 2002
Creator: Hosokawa, Ketia
System: The UNT Digital Library
IMPROVING THE PHYSICS IMPACT OF NEXT-GENERATION 76GE NEUTRINOLESS DOUBLE-BETA DECAY EXPERIMENTS (open access)

IMPROVING THE PHYSICS IMPACT OF NEXT-GENERATION 76GE NEUTRINOLESS DOUBLE-BETA DECAY EXPERIMENTS

Summary and Conclusions - It was shown that segmentation and pulse-shape discrimination can improve the discovery sensitivity of a next-gen 0vBB-decay experiment by 90%. - However, when practical aspects are considered (such as instrumenting each segment with front-end electronics), the discovery sensitivity is decreased by 19%. - This has extremely important consequences to proposed next-gen experiments since the two active collaborations have strongly advocated the use of segmented detectors for all or part of the experiment. - New germanium detector technology, currently under development, has demonstrated excellent multi-site background rejection capabilities without the complexity of segmentation or complicated PSD algorithms. - The physically-segmented p-type germanium detector technology has proven to be a useful and practical tool in modern nuclear physics. The PSEG technology deserves further development as it has the potential for use in a variety of applications.
Date: June 2009
Creator: Hossbach, Todd W.
System: The UNT Digital Library
A Study of The Standard Model Higgs, WW and ZZ Production in Dilepton Plus Missing Transverse Energy Final State at CDF Run II (open access)

A Study of The Standard Model Higgs, WW and ZZ Production in Dilepton Plus Missing Transverse Energy Final State at CDF Run II

We report on a search for Standard Model (SM) production of Higgs to WW* in the two charged lepton (e, {mu}) and two neutrino final state in p{bar p} collisions at a center of mass energy {radical}s = 1.96 TeV. The data were collected with the CDF II detector at the Fermilab Tevatron and correspond to an integrated luminosity of 1.9fb{sup -1}. The Matrix Element method is developed to calculate the event probability and to construct a likelihood ratio discriminator. There are 522 candidates observed with an expectation of 513 {+-} 41 background events and 7.8 {+-} 0.6 signal events for Higgs mass 160GeV/c{sup 2} at next-to-next-to-leading logarithmic level calculation. The observed 95% C.L. upper limit is 0.8 pb which is 2.0 times the SM prediction while the median expected limit is 3.1{sub -0.9}{sup +1.3} with systematics included. Results for 9 other Higgs mass hypotheses ranging from 110GeV/c{sup 2} to 200GeV/c{sup 2} are also presented. The same dilepton plus large transverse energy imbalance (E{sub T}) final state is used in the SM ZZ production search and the WW production study. The observed significance of ZZ {yields} ll{nu}{nu} channel is 1.2{sigma}. It adds extra significance to the ZZ {yields} 4l channel …
Date: June 1, 2008
Creator: Hsu, Shih-Chieh & /UC, San Diego
System: The UNT Digital Library
The Theory of Random Laser Systems (open access)

The Theory of Random Laser Systems

Studies of random laser systems are a new direction with promising potential applications and theoretical interest. The research is based on the theories of localization and laser physics. So far, the research shows that there are random lasing modes inside the systems which is quite different from the common laser systems. From the properties of the random lasing modes, they can understand the phenomena observed in the experiments, such as multi-peak and anisotropic spectrum, lasing mode number saturation, mode competition and dynamic processes, etc. To summarize, this dissertation has contributed the following in the study of random laser systems: (1) by comparing the Lamb theory with the Letokhov theory, the general formulas of the threshold length or gain of random laser systems were obtained; (2) they pointed out the vital weakness of previous time-independent methods in random laser research; (3) a new model which includes the FDTD method and the semi-classical laser theory. The solutions of this model provided an explanation of the experimental results of multi-peak and anisotropic emission spectra, predicted the saturation of lasing modes number and the length of localized lasing modes; (4) theoretical (Lamb theory) and numerical (FDTD and transfer-matrix calculation) studies of the origin of …
Date: June 27, 2002
Creator: Jiang, Xunya
System: The UNT Digital Library
The VRFurnace: A Virtual Reality Application for Energy System Data Analysis (open access)

The VRFurnace: A Virtual Reality Application for Energy System Data Analysis

The VRFurnace is a unique VR application designed to analyze a complete coal-combustion CFD model of a power plant furnace. Although other applications have been created that analyze furnace performance, no other has included the added complications of particle tracking and the reactions associated with coal combustion. Currently the VRFurnace is a versatile analysis tool. Data translators have been written to allow data from most of the major commercial CFD software packages as well as standard data formats of hand-written code to be uploaded into the VR application. Because of this almost any type of CFD model of any power plant component can be analyzed immediately. The ease of use of the VRFurnace is another of its qualities. The menu system created for the application not only guides first time users through the various button combinations but it also helps the experienced user keep track of which tool is being used. Because the VRFurnace was designed for use in the C6 device at Iowa State University's Virtual Reality Applications Center it is naturally a collaborative project. The projection-based system allows many people to be involved in the analysis process. This type of environment opens the design process to not only …
Date: June 25, 2001
Creator: Johnson, Peter Eric
System: The UNT Digital Library