A search for sterile neutrinos in MINOS (open access)

A search for sterile neutrinos in MINOS

MINOS, the Main Injector Neutrino Oscillation Search, is a long baseline neutrino oscillation experiment based at Fermilab National Accelerator Laboratory. The experiment uses a neutrino beam, which is measured 1 km downstream from its origin in the Near detector at Fermilab and then 735 km later in the Far detector at the Soudan mine. By comparing these two measurements, MINOS can attain a very high precision for parameters in the atmospheric sector of neutrino oscillations. In addition to precisely determining {Delta}m{sub 23}{sup 2} and {theta}{sub 23} through the disappearance of {nu}{sub {mu}}, MINOS is able to measure {nu}{sub {mu}} {yields} {nu}{sub sterile} by looking for a deficit in the number of neutral current interactions seen in the Far detector. In this thesis, we present the results of a search for sterile neutrinos in MINOS.
Date: December 1, 2007
Creator: Osiecki, Thomas Henry
System: The UNT Digital Library
First observation of the decay B bar 0s -->; D+-s K-+ and measurement of Br(B bar 0s -->; D+-sK-+)/Br(B bar 0s -->; D+s pi-) (open access)

First observation of the decay B bar 0s -->; D+-s K-+ and measurement of Br(B bar 0s -->; D+-sK-+)/Br(B bar 0s -->; D+s pi-)

None
Date: November 15, 2007
Creator: Muelmenstaedt, Johannes & Muelmenstaedt, Johannes
System: The UNT Digital Library
Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System (open access)

Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System

The authors present precision measurements of the direct CP violation parameter, Re({epsilon}{prime}/{epsilon}), the kaon parameters, {Delta}m and {tau}{sub S}, and the CPT tests, {phi}{sub {+-}} and {Delta}{phi}, in neutral kaon decays. These results are based on the full dataset collected by the KTeV experiment at Fermi National Accelerator Laboratory during 1996, 1997, and 1999. This dataset contains {approx} 15 million K {yields} {pi}{sup 0}{pi}{sup 0} decays and {approx} 69 million K {yields} {pi}{sup +}{pi}{sup -} decays. They describe significant improvements to the precision of these measurements relative to previous KTeV analyses. They find Re({epsilon}{prime}/{epsilon}) = [19.2 {+-} 1.1(stat) {+-} 1.8(syst)] x 10{sup -4}, {Delta}m = (5265 {+-} 10) x 10{sup 6} hs{sup -1}, and {tau}{sub S} = (89.62 {+-} 0.05) x 10{sup -12} s. They measure {phi}{sub {+-}} = (44.09 {+-} 1.00){sup o} and {Delta}{phi} = (0.29 {+-} 0.31){sup o}; these results are consistent with CPT symmetry.
Date: December 1, 2007
Creator: Worcester, Elizabeth Turner
System: The UNT Digital Library
A measurement of the top quark's charge (open access)

A measurement of the top quark's charge

The top quark was discovered in 1995 at the Fermilab National Accelerator Laboratory (Fermilab). One way to confirm if the observed top quark is really the top quark posited in the Standard Model (SM) is to measure its electric charge. In the Standard Model the top quark is the isospin partner of the bottom quark and is expected to have a charge of +2/3. However, an alternative 'exotic' model has been proposed with a fourth generation exotic quark that has the same characteristics, such as mass, as our observed top but with a charge of -4/3. This thesis presents the first CDF measurement of the top quark's charge via its decay products, a W boson and a bottom quark, using {approx} 1 fb{sup -1} of data. The data were collected by the CDF detector from proton anti-proton (p{bar p}) collisions at {radical}s = 1.96 TeV at Fermilab. We classify events depending on the charges of the bottom quark and associated W boson and count the number of events which appear 'SM-like' or 'exotic-like' with a SM-like event decaying as t {yields} W{sup +}b and an exotic event as t {yields} W{sup -}b. We find the p-value under the Standard Model …
Date: November 1, 2007
Creator: Unalan, Zeynep Gunay
System: The UNT Digital Library
Processing and Protection of Rare Earth Permanent Magnet Particulate for Bonded Magnet Applications (open access)

Processing and Protection of Rare Earth Permanent Magnet Particulate for Bonded Magnet Applications

Rapid solidification of novel mixed rare earth-iron-boron, MRE{sub 2}Fe{sub 14}B (MRE = Nd, Y, Dy; currently), magnet alloys via high pressure gas atomization (HPGA) have produced similar properties and structures as closely related alloys produced by melt spinning (MS) at low wheel speeds. Recent additions of titanium carbide and zirconium to the permanent magnet (PM) alloy design in HPGA powder (using He atomization gas) have made it possible to achieve highly refined microstructures with magnetic properties approaching melt spun particulate at cooling rates of 10{sup 5}-10{sup 6}K/s. By producing HPGA powders with the desirable qualities of melt spun ribbon, the need for crushing ribbon was eliminated in bonded magnet fabrication. The spherical geometry of HPGA powders is more ideal for processing of bonded permanent magnets since higher loading fractions can be obtained during compression and injection molding. This increased volume loading of spherical PM powder can be predicted to yield a higher maximum energy product (BH){sub max} for bonded magnets in high performance applications. Passivation of RE-containing powder is warranted for the large-scale manufacturing of bonded magnets in applications with increased temperature and exposure to humidity. Irreversible magnetic losses due to oxidation and corrosion of particulates is a known drawback …
Date: December 1, 2007
Creator: Sokolowski, Peter Kelly
System: The UNT Digital Library
M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications (open access)

M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti{sub 5}Si{sub 3}-based alloys was investigated. Oxidation behavior of Ti{sub 5}Si{sub 3}-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti{sub 5}Si{sub 3} by nucleation and growth of nitride subscale. Ti{sub 5}Si{sub 3.2} and Ti{sub 5}Si{sub 3}C{sub 0.5} alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi{sub 2} coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo{sub 3}Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo{sub 3}Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nb{sub ss} …
Date: December 1, 2007
Creator: Tang, Zhihong
System: The UNT Digital Library
A measurement of the top quark mass in 1.96 TeV proton-antiproton collisions using a novel matrix element method (open access)

A measurement of the top quark mass in 1.96 TeV proton-antiproton collisions using a novel matrix element method

A measurement of the top quark mass in t{bar t} {yields} l + jets candidate events, obtained from p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector, is presented. The measurement approach is that of a matrix element method. For each candidate event, a two dimensional likelihood is calculated in the top pole mass and a constant scale factor, 'JES', where JES multiplies the input particle jet momenta and is designed to account for the systematic uncertainty of the jet momentum reconstruction. As with all matrix elements techniques, the method involves an integration using the Standard Model matrix element for tt production and decay. however, the technique presented is unique in that the matrix element is modified to compensate for kinematic assumptions which are made to reduce computation time. Background events are dealt with through use of an event observable which distinguishes signal from background, as well as through a cut on the value of an event's maximum likelihood. Results are based on a 955 pb{sup -1} data sample, using events with a high-p{sub T} lepton and exactly four high-energy jets, at least one of which is tagged as coming from a …
Date: December 1, 2007
Creator: Freeman, John C.
System: The UNT Digital Library
A search for z boson pair production at the Fermilab Tevatron Collider (open access)

A search for z boson pair production at the Fermilab Tevatron Collider

This dissertation describes a search for Z/{gamma}* boson pair production decaying into {mu}{mu}{mu}{mu}, {mu}{mu}ee, and eeee final states with approximately 1 fb{sup -1} of data at the Fermilab Tevatron Collider at {radical}s = 1.96 TeV. The small cross section times branching ratio for each channel mandated a thorough study of the acceptance and efficiencies. After optimization, 1.7 {+-} 0.1 events are expected for Standard Model production with a background of 0.13 {+-} 0.03 events. One event was found in the {mu}{mu}ee channel. A cross section limit of 4.4 pb is determined at a 95% confidence level for Standard Model production. Additionally, one parameter and two parameter 95% C.L. limits are found for the anomalous neutral trilinear gauge couplings ZZZ* and ZZ{gamma}*. The one parameter 95% C.L. coupling limits with a form factor scale of 1.2 TeV are: -0.28 < f{sub 40}{sup Z} < 0.28, -0.31 < f{sub 50}{sup Z} < 0.29, -0.26 < f{sub 40}{gamma} < 0.26, and -0.30 < f{sub 50}{sup {gamma}} < 0.28.
Date: October 1, 2007
Creator: Jarvis, Chad Ryan
System: The UNT Digital Library
Measurement of the Inclusive Branching FractionsB(B^- to D^+ Pi^- Pi^-) and B(B^- to D*^+ Pi^- Pi^-) (open access)

Measurement of the Inclusive Branching FractionsB(B^- to D^+ Pi^- Pi^-) and B(B^- to D*^+ Pi^- Pi^-)

The D{sub J}{sup 0} is a family of four orbitally excited mesons: D*{sub 2}(2460){sup 0}, D{sub 1}(2420){sup 0}, D{sub 1}(j = 1/2){sup -}, and D*{sub 0}(j = 1/2){sup 0}. This dissertation presents the measurements of the inclusive branching fractions, {Beta}(B{sup -} {yields} D*{sup +}{pi}{sup -}{pi}{sup -}) and {Beta}(B{sup -} {yields} D{sup +}{pi}{sup -}{pi}{sup -}). The D{sub J}{sup 0} provides an intermediate resonance for those two modes. The data used for this analysis consists of Runs 1-5 with total integrated luminosity of 343.38 fb{sup -1}, which is corresponding to 383.92 million B{bar B} pairs, provided by the BABAR detector at the PEP-II asymmetric B Factory. The values presented are: {Beta}(B{sup -} {yields} D{sup +}{pi}{sup -}{pi}{sup -}) = (1.12 {+-} 0.02 {+-} 0.08) x 10{sup -3}; {Beta}(B{sup -} {yields} D*{sup +}{pi}{sup -}{pi}{sup -}) = (1.67 {+-} 0.03 {+-} 0.13) x 10{sup -3}.
Date: July 17, 2007
Creator: Eschenburg, Vance Onno & U., /Mississippi
System: The UNT Digital Library
Analysis of Protein-RNA and Protein-Peptide Interactions in Equine Infectious Anemia (open access)

Analysis of Protein-RNA and Protein-Peptide Interactions in Equine Infectious Anemia

Macromolecular interactions are essential for virtually all cellular functions including signal transduction processes, metabolic processes, regulation of gene expression and immune responses. This dissertation focuses on the characterization of two important macromolecular interactions involved in the relationship between Equine Infectious Anemia Virus (EIAV) and its host cell in horse: (1) the interaction between the EIAV Rev protein and its binding site, the Rev-responsive element (RRE) and (2) interactions between equine MHC class I molecules and epitope peptides derived from EIAV proteins. EIAV, one of the most divergent members of the lentivirus family, has a single-stranded RNA genome and carries several regulatory and structural proteins within its viral particle. Rev is an essential EIAV regulatory encoded protein that interacts with the viral RRE, a specific binding site in the viral mRNA. Using a combination of experimental and computational methods, the interactions between EIAV Rev and RRE were characterized in detail. EIAV Rev was shown to have a bipartite RNA binding domain contain two arginine rich motifs (ARMs). The RRE secondary structure was determined and specific structural motifs that act as cis-regulatory elements for EIAV Rev-RRE interaction were identified. Interestingly, a structural motif located in the high affinity Rev binding site is …
Date: December 1, 2007
Creator: Lee, Jae-Hyung
System: The UNT Digital Library
Search for stop pairs in the emu channel (open access)

Search for stop pairs in the emu channel

The Standard Model gives a satisfying description of subatomic processes at low energy (< 1 TeV). Beyond this energy scale, other models must be considered. Supersymmetry is one of them. It gives in an elegant way, solutions to several Standard Model short comings. This document reports the search for a supersymmetric signal characterized by the production of two stops decaying into two b-jets, one electron, one muon and missing energy. This study has been performed at the D0 experiment, located on the ring of Tevatron collider at FermiLab, (Chicago, USA), whose energy in the center of mass reaches {radical}s = 1.96 TeV. The data used for this analysis have been collected during Run IIa of D0 detector; from april 2003 to march 2006 ({approx} 1fb{sup -1}). The objects handled for this analysis require a good understanding of both calorimeters, muon detectors and trackers. As Tevatron is an hadronic collider and the number of Standard Model processes with the same signature as the signal is low, the background is thus dominated by QCD processes. After the selection cuts, no excess of data has been observed with respect to the Standard Model expectation. D0 experiment sensibility has been improved and the 95% …
Date: October 1, 2007
Creator: Tissandier, Fabrice & U., /Clermont-Ferrand
System: The UNT Digital Library
Time Dependent CP Asymmetries and Branching RatioMeasurements in Charmless Three Body B Decays at BABAR (open access)

Time Dependent CP Asymmetries and Branching RatioMeasurements in Charmless Three Body B Decays at BABAR

In this work we presented measurements of CP violation and decay rates of B decays in final states not involving a charm quark in the final state. In particular, the time-dependent CP asymmetries of decays which proceed through b {yields} s elementary transition is a particularly sensitive probe of physics beyond the Standard Model. In fact, even if the precise measurements of CP conserving and CP violating processes show the success of the CKM picture of the flavour physics, the sector of b {yields} s transitions is still not strongly constrained and leaves room for new physics contributions. In particular, we considered the decays which have the cleanest theoretical prediction within the Standard Model: B{sup 0} {yields} {phi}K{sup 0} and B{sup 0} {yields} K{sub s}{sup 0}K{sub s}{sup 0}K{sub s}{sup 0} {beta}{sub eff}{sup SM} = 0.379. We examined the former with a completely new approach with respect to the past: the study of CP violation in the whole K{sup +}K{sup -}K{sup 0} phase space through a time-dependent Dalitz plot analysis. With this approach, we simultaneously measured the CP-violating asymmetries of the {phi}KJ{sup 0}, f{sub 0}(980)K{sup 0} resonant and K{sup +}K{sup -}K{sup 0} non-resonant contributions, avoiding one of the largest uncertainties which …
Date: July 17, 2007
Creator: Di Marco, Emanuele & U., /Rome
System: The UNT Digital Library
Control of Laser Plasma Based Accelerators up to 1 GeV (open access)

Control of Laser Plasma Based Accelerators up to 1 GeV

This dissertation documents the development of a broadband electron spectrometer (ESM) for GeV class Laser Wakefield Accelerators (LWFA), the production of high quality GeV electron beams (e-beams) for the first time in a LWFA by using a capillary discharge guide (CDG), and a statistical analysis of CDG-LWFAs. An ESM specialized for CDG-LWFAs with an unprecedented wide momentum acceptance, from 0.01 to 1.1 GeV in a single shot, has been developed. Simultaneous measurement of e-beam spectra and output laser properties as well as a large angular acceptance (> {+-} 10 mrad) were realized by employing a slitless scheme. A scintillating screen (LANEX Fast back, LANEX-FB)--camera system allowed faster than 1 Hz operation and evaluation of the spatial properties of e-beams. The design provided sufficient resolution for the whole range of the ESM (below 5% for beams with 2 mrad divergence). The calibration between light yield from LANEX-FB and total charge, and a study on the electron energy dependence (0.071 to 1.23 GeV) of LANEX-FB were performed at the Advanced light source (ALS), Lawrence Berkeley National Laboratory (LBNL). Using this calibration data, the developed ESM provided a charge measurement as well. The production of high quality electron beams up to 1 GeV …
Date: December 3, 2007
Creator: Nakamura, Kei
System: The UNT Digital Library
Search for new physics coupling to the z boson (open access)

Search for new physics coupling to the z boson

We present the results of two searches for new particles that couple Z bosons in p{bar p} collisions at {radical}s = 1.96 TeV using the Collider Detector at Fermilab (CDF). In the first, we search for a long-lived parent of the Z boson using a data sample with a luminosity of 163 pb{sup -1}. Finding no significant excess above background, we set a limit on a fourth generation model as a function of mass and lifetime. In the second, we search for a particle that decays to a Z boson in conjunction with jets using a data sample with a luminosity of 1.06 fb{sup -1}. Finding no significant excess above background, we set a limit on a fourth generation model as a function of mass.
Date: June 1, 2007
Creator: Scott, Adam Liddle
System: The UNT Digital Library
Measurements of CP asymmetries and branching fractions of two-body charmless decays of B^0 and B^0_s mesons (open access)

Measurements of CP asymmetries and branching fractions of two-body charmless decays of B^0 and B^0_s mesons

The thesis is organized as follows: Chapter 1 describes the theoretical framework of non-leptonic B{sub (s)}{sup 0} {yields} H{sup +}h{prime}{sup -} decays, with a simple overview of the CP violation mechanism within the Standard Model and of the most used phenomenological approaches in the evaluation of strong interaction contributions. The chapter contains also a review of the theoretical expectations and the current experimental measurements along with a discussion about the importance of studying such decays. Chapter 2 contains a general description of the Tevatron collider and of the CDF II detector. Chapter 3 is devoted to the description of the data sample used for the measurement and the method used in extracting the signal from the background. Particular attention is dedicated to the on-line trigger selection, which is crucial to collect a sample enriched in B{sub (s)}{sup 0} {yields} h{sup +}h{prime}{sup -} decays. Chapter 4 shows how the information from kinematics and particle identification was used to achieve a statistical discrimination amongst modes to extract individual measurements. The available resolutions in mass or in particle identification are separately insufficient for an event-by-event separation of B{sub (s)}{sup 0} {yields} h{sup +}h{prime}{sup -} modes. The choice of observables and the technique used …
Date: December 1, 2007
Creator: Morello, Michael Joseph & /Pisa, Scuola Normale Superiore
System: The UNT Digital Library
Diffractive Z/gamma* --> mu+mu- boson production in proton - antiproton collisions (open access)

Diffractive Z/gamma* --> mu+mu- boson production in proton - antiproton collisions

Measurements of the inclusive diffractive Z {yields} {mu}{sup +}{mu}{sup -} cross section with gap requirement for M{sub {mu}}{sub {mu}} > 40 GeV at {radical} s = 1.96 TeV and fraction of Z bosons produced diffractively with gap requirement from Z inclusive production are presented. The measurements are performed using a data sample corresponding to an integrated luminosity of 820 pb{sup -1}, collected with the D0 detector at the Tevatron, between 2002 to 2005. A total of 39945 di-muons events are selected and final results of: {sigma}{sub Diff}{sup gap} x Br(Z/{gamma}* {yields} {mu}{sup +}{mu}{sup -}) = 4.09 {+-} 0.64(stat.) {+-} 0.88(syst.) {+-} 0.27(lumi.) pb and, R{sub Diff}{sup gap} = 1.92 {+-} 0.30(stat.) {+-} 0.41(syst.) {+-} 0.12(lumi) % are obtained. In addition, d{sigma}/d{zeta} and d{sigma}/dy distributions are presented and they are compared with diffractive montecarlo (POMWIG). A reasonable agreement is obtained in this comparation. Finally, comparison of fraction of Z bosons produced diffractively with gap requirement (gap fraction) as measured with D0 during Run I of the Tevatron is compared. A good agreement is found for gap fraction results.
Date: July 1, 2007
Creator: Mendoza Navas, Luis Miguel
System: The UNT Digital Library
Measurement of the Diphoton Differential Cross Section in p anti-p Collisions at s**(1/2) = 1.96-TeV (open access)

Measurement of the Diphoton Differential Cross Section in p anti-p Collisions at s**(1/2) = 1.96-TeV

The diphoton differential cross-section as a function of mass up to 300 GeV/c{sup 2}, q{sub T} up to 100 GeV/c, and opening angle over a range of 0 to {pi} radians is measured. The measurement is performed using 1046.19 pb{sup -1} of data collected at Fermi National Accelerator Laboratory using the D0 detector. This analysis considers all direct diphoton states but attempts to suppress contributions due to fragmentation.
Date: January 1, 2007
Creator: Dyer, Joshua Marc
System: The UNT Digital Library
An atmospheric muon neutrino disappearance measurement with the MINOS far detector (open access)

An atmospheric muon neutrino disappearance measurement with the MINOS far detector

It is now widely accepted that the Standard Model assumption of massless neutrinos is wrong, due primarily to the observation of solar and atmospheric neutrino flavor oscillations by a small number of convincing experiments. The MINOS Far Detector, capable of observing both the outgoing lepton and associated showering products of a neutrino interaction, provides an excellent opportunity to independently search for an oscillation signature in atmospheric neutrinos. To this end, a MINOS data set from an 883 live day, 13.1 kt-yr exposure collected between July, 2003 and April, 2007 has been analyzed. 105 candidate charged current muon neutrino interactions were observed, with 120.5 {+-} 1.3 (statistical error only) expected in the absence of oscillation. A maximum likelihood analysis of the observed log(L/E) spectrum shows that the null oscillation hypothesis is excluded at over 96% confidence and that the best fit oscillation parameters are sin{sup 2} 2{theta}{sub 23} = 0.95{sub -0.32} and {Delta}m{sub 23}{sup 2} = 0.93{sub -0.44}{sup +3.94} x 10{sup -3} eV{sup 2}. This measurement of oscillation parameters is consistent with the best fit values from the Super-Kamiokande experiment at 68% confidence.
Date: December 1, 2007
Creator: Gogos, Jeremy Peter
System: The UNT Digital Library
Mechanisms Associated with Rumpling of Pt-Modified Beta-NiAl Coatings (open access)

Mechanisms Associated with Rumpling of Pt-Modified Beta-NiAl Coatings

The formation of surface undulations (i.e. rumpling) at the bond coat/thermally grown oxide (TGO) interface has been shown to cause failure by spallation of the ceramic top coat in aero-turbine systems. Many mechanisms have been proposed concerning the cause of these surface distortions; however, there is little agreement on what may be the dominating cause of the rumpling behavior. Of there mechanisms, the reversible phase transformation from a cubic {beta}-NiAl structure to a face centered tetragonal (FCT) martensitic phase was of particular interest because of its ability to form surface rumpling in Pt-modified {beta} bulk alloys. However, the bulk alloys used in obtaining that result were simple ternary systems and not relevant to actual coating compositions as other alloying elements enter the coating due to coating/substrate interdiffusion at high temperature. In the current study, the depletion behavior of a commercial coating was studied. Compositions from the depletion path were determined and bulk alloys representing these coating compositions were prepared. The martensitic phase transformation was then characterized using DSC and XRD. The martensitic start temperature on cooling, Ms, was consistently found to be significantly lower than previously reported values (e.g. 530 C vs 100 C). Because of the low Ms temperature, …
Date: December 1, 2007
Creator: Henderkott, Joseph Peter
System: The UNT Digital Library
Seismic velocity estimation from time migration (open access)

Seismic velocity estimation from time migration

This is concerned with imaging and wave propagation in nonhomogeneous media, and includes a collection of computational techniques, such as level set methods with material transport, Dijkstra-like Hamilton-Jacobi solvers for first arrival Eikonal equations and techniques for data smoothing. The theoretical components include aspects of seismic ray theory, and the results rely on careful comparison with experiment and incorporation as input into large production-style geophysical processing codes. Producing an accurate image of the Earth's interior is a challenging aspect of oil recovery and earthquake analysis. The ultimate computational goal, which is to accurately produce a detailed interior map of the Earth's makeup on the basis of external soundings and measurements, is currently out of reach for several reasons. First, although vast amounts of data have been obtained in some regions, this has not been done uniformly, and the data contain noise and artifacts. Simply sifting through the data is a massive computational job. Second, the fundamental inverse problem, namely to deduce the local sound speeds of the earth that give rise to measured reacted signals, is exceedingly difficult: shadow zones and complex structures can make for ill-posed problems, and require vast computational resources. Nonetheless, seismic imaging is a crucial part …
Date: May 31, 2007
Creator: Cameron, Maria Kourkina
System: The UNT Digital Library
Sum Frequency Generation Vibrational Spectroscopy Studies on ModelPeptide Adsorption at the Hydrophobic Solid-Water and HydrophilicSolid-Water Interfaces (open access)

Sum Frequency Generation Vibrational Spectroscopy Studies on ModelPeptide Adsorption at the Hydrophobic Solid-Water and HydrophilicSolid-Water Interfaces

Sum frequency generation (SFG) vibrational spectroscopy has been used to study the interfacial structure of several polypeptides and amino acids adsorbed to hydrophobic and hydrophilic surfaces under a variety of experimental conditions. Peptide sequence, peptide chain length, peptide hydrophobicity, peptide side-chain type, surface hydrophobicity, and solution ionic strength all affect an adsorbed peptide's interfacial structure. Herein, it is demonstrated that with the choice of simple, model peptides and amino acids, surface specific SFG vibrational spectroscopy can be a powerful tool to elucidate the interfacial structure of these adsorbates. Herein, four experiments are described. In one, a series of isosequential amphiphilic peptides are synthesized and studied when adsorbed to both hydrophobic and hydrophilic surfaces. On hydrophobic surfaces of deuterated polystyrene, it was determined that the hydrophobic part of the peptide is ordered at the solid-liquid interface, while the hydrophilic part of the peptide appears to have a random orientation at this interface. On a hydrophilic surface of silica, it was determined that an ordered peptide was only observed if a peptide had stable secondary structure in solution. In another experiment, the interfacial structure of a model amphiphilic peptide was studied as a function of the ionic strength of the solution, a …
Date: December 19, 2007
Creator: York, Roger L.
System: The UNT Digital Library
A measurement of the lambda_b lifetime at the D0 experiment (open access)

A measurement of the lambda_b lifetime at the D0 experiment

This thesis describes a measurement of the lifetime of the {Lambda}{sub b}{sup 0} baryon, performed using data from proton-antiproton collisions at a centre of mass energy of 1.96 TeV. The decay {Lambda}{sub b}{sup 0} {yields} {Lambda}{sub c}{sup +}{mu}{sup -}{ovr P{nu}}{sub {mu}}X was reconstructed in approximately 1.3 fb{sup -1} of data recorded by the D0 detector in 2002-2006 during Run II of the Fermilab Tevatron collider. A signal of 4437 {+-} 329 {Lambda}{sub c}{sup +}{mu}{sup -} pairs was obtained, and the {Lambda}{sub b}{sup 0} lifetime was measured using a binned {chi}{sup 2} fit, which gives a value {tau}({Lambda}{sub b}{sup 0}) = 1.290{sub -0.110}{sup +0.119}(stat){sub -0.091}{sup +0.085}(syst) ps. This result is consistent with the world average and is one of the most precise measurements of this quantity.
Date: July 1, 2007
Creator: Lewin, Marcus Philip
System: The UNT Digital Library
Development and Integration of Hardware and Software for Active-Sensors in Structural Monitoring (open access)

Development and Integration of Hardware and Software for Active-Sensors in Structural Monitoring

Structural Health Monitoring (SHM) promises to deliver great benefits to many industries. Primarily among them is a potential for large cost savings in maintenance of complex structures such as aircraft and civil infrastructure. However, several large obstacles remain before widespread use on structures can be accomplished. The development of three components would address many of these obstacles: a robust sensor validation procedure, a low-cost active-sensing hardware and an integrated software package for transition to field deployment. The research performed in this thesis directly addresses these three needs and facilitates the adoption of SHM on a larger scale, particularly in the realm of SHM based on piezoelectric (PZT) materials. The first obstacle addressed in this thesis is the validation of the SHM sensor network. PZT materials are used for sensor/actuators because of their unique properties, but their functionality also needs to be validated for meaningful measurements to be recorded. To allow for a robust sensor validation algorithm, the effect of temperature change on sensor diagnostics and the effect of sensor failure on SHM measurements were classified. This classification allowed for the development of a sensor diagnostic algorithm that is temperature invariant and can indicate the amount and type of sensor failure. …
Date: October 15, 2007
Creator: Overly, Timothy G.S.
System: The UNT Digital Library
Dalitz Analysis of D0 to K0(S) Pi+ Pi- and Measurement of the CKM Angle Gamma in Charged B+- Decays to D(*) K+- Decays (open access)

Dalitz Analysis of D0 to K0(S) Pi+ Pi- and Measurement of the CKM Angle Gamma in Charged B+- Decays to D(*) K+- Decays

Despite more than thirty years having elapsed since the discovery of CP violation, our understanding about the source and the nature of this phenomenon is still very limited. In the standard model of particle physics, CP violation is due to the presence of an non-irreducible weak phase in the Cabibbo-Kabayashi-Maskawa(CKM) matrix. Up to now, all the experimental results are in good agreement with the standard model. However, it is important for us to over-constrain the CKM quark-mixing matrix and explore the possibility of new physics beyond the standard model. The B meson provides an ideal place to measure CP violation due to its heavy mass and potentially large CP-violating effects. In particular, the angle {gamma} of the Unitary Triangle relating the elements of the CKM matrix is extremely crucial in terms of CP violation and constraints on the new physics models. Various methods using B{sup -} {yields} D{sup 0}K{sup -} decays have been proposed to measure based on the interference between the V{sub cb} and V{sub ub} amplitudes. Despite the simple concept, the measurement turns out to be experimentally challenging due to the small branching fraction and the small value of {tau}{sub B}, the amplitude ratio between the two contributing …
Date: July 10, 2007
Creator: Lau, Yan-Pan
System: The UNT Digital Library