Month

Language

Measurement of the W boson helicity in t anti-t decays (open access)

Measurement of the W boson helicity in t anti-t decays

None
Date: June 1, 2005
Creator: Schmitt, Christian & U., /Wuppertal
System: The UNT Digital Library
Search for a new charged heavy vector boson decaying to an electron-neutrino pair in p anti-p collisions at s**(1/2) = 1.96 TeV (open access)

Search for a new charged heavy vector boson decaying to an electron-neutrino pair in p anti-p collisions at s**(1/2) = 1.96 TeV

We present results on a search for a heavy charged vector boson, W', decaying to an electron-neutrino pair in p{bar p} collisions at {radical}s = 1.96 TeV using a data sample corresponding to an integrated luminosity of 205 pb{sup -1}. We found no evidence of this decay channel, and set 95% confidence level limits on the production cross section times branching fraction assuming the light neutrino. We also set the limit on the W' boson mass at M{sub W'} > 788 GeV/c{sup 2}, assuming the standard model strength couplings.
Date: June 1, 2005
Creator: Kim, Jieun & U., /Kyungpook Natl.
System: The UNT Digital Library
Potential Release Site Sediment Concentrations Correlated to Storm Water Station Runoff through GIS Modeling (open access)

Potential Release Site Sediment Concentrations Correlated to Storm Water Station Runoff through GIS Modeling

This research examined the relationship between sediment sample data taken at Potential Release Sites (PRSs) and storm water samples taken at selected sites in and around Los Alamos National Laboratory (LANL). The PRSs had been evaluated for erosion potential and a matrix scoring system implemented. It was assumed that there would be a stronger relationship between the high erosion PRSs and the storm water samples. To establish the relationship, the research was broken into two areas. The first area was raster-based modeling, and the second area was data analysis utilizing the raster based modeling results and the sediment and storm water sample results. Two geodatabases were created utilizing raster modeling functions and the Arc Hydro program. The geodatabase created using only Arc Hydro functions contains very fine catchment drainage areas in association with the geometric network and can be used for future contaminant tracking. The second geodatabase contains sub-watersheds for all storm water stations used in the study along with a geometric network. The second area of the study focused on data analysis. The analytical sediment data table was joined to the PRSs spatial data in ArcMap. All PRSs and PRSs with high erosion potential were joined separately to create …
Date: June 1, 2005
Creator: McLean, C.T.
System: The UNT Digital Library
Angular-momentum-dominated electron beams and flat-beam generation (open access)

Angular-momentum-dominated electron beams and flat-beam generation

In the absence of external forces, if the dynamics within an electron beam is dominated by its angular momentum rather than other effects such as random thermal motion or self Coulomb-repulsive force (i.e., space-charge force), the beam is said to be angular-momentum-dominated. Such a beam can be directly applied to the field of electron-cooling of heavy ions; or it can be manipulated into an electron beam with large transverse emittance ratio, i.e., a flat beam. A flat beam is of interest for high-energy electron-positron colliders or accelerator-based light sources. An angular-momentum-dominated beam is generated at the Fermilab/NICADD photoinjector Laboratory (FNPL) and is accelerated to an energy of 16 MeV. The properties of such a beam is investigated systematically in experiment. The experimental results are in very good agreement with analytical expectations and simulation results. This lays a good foundation for the transformation of an angular-momentum-dominated beam into a flat beam. The round-to-flat beam transformer is composed of three skew quadrupoles. Based on a good knowledge of the angular-momentum-dominated beam, the quadrupoles are set to the proper strengths in order to apply a total torque which removes the angular momentum, resulting in a flat beam. For bunch charge around 0.5 nC, …
Date: June 1, 2005
Creator: Sun, Yin-e
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
Search for electroweak single top quark production with cdf in proton - anti-proton collisions at s**(1/2) = 1.96-TeV (open access)

Search for electroweak single top quark production with cdf in proton - anti-proton collisions at s**(1/2) = 1.96-TeV

In this thesis two searches for electroweak single top quark production with the CDF experiment have been presented, a cutbased search and an iterated discriminant analysis. Both searches find no significant evidence for electroweak single top production using a data set corresponding to an integrated luminosity of 162 pb{sup -1} collected with CDF. Therefore limits on s- and t-channel single top production are determined using a likelihood technique. For the cutbased search a likelihood function based on lepton charge times pseudorapidity of the non-bottom jet was used if exactly one bottom jet was identified in the event. In case of two identified bottom jets a likelihood function based on the total number of observed events was used. The systematic uncertainties have been treated in a Bayesian approach, all sources of systematic uncertainties have been integrated out. An improved signal modeling using the MadEvent Monte Carlo program matched to NLO calculations has been used. The obtained limits for the s- and t-channel single top production cross sections are 13.6 pb and 10.1 pb, respectively. To date, these are most stringent limits published for the s- and the t-channel single top quark production modes.
Date: June 1, 2005
Creator: Walter, Thorsten & /Karlsruhe U., EKP
System: The UNT Digital Library
Angular correlations in beauty production at the Tevatron at sqrt(s) = 1.96 TeV (open access)

Angular correlations in beauty production at the Tevatron at sqrt(s) = 1.96 TeV

Measurements of the b quark production cross section at the Tevatron and at Hera in the final decades of the 20th century have consistently yielded higher values than predicted by Next-to-Leading Order (NLO) QCD. This discrepancy has led to a large efforts by theorists to improve theoretical calculations of the cross sections and simulations of b quark production. As a result, the difference between theory and experiment has been much reduced. New measurements are needed to test the developments in the calculations and in event simulation. In this thesis, a measurement of angular correlations between b jets produced in the same event is presented. The angular separation between two b jets is directly sensitive to higher order contributions. In addition, the measurement does not depend strongly on fragmentation models or on the experimental luminosity and efficiency, which lead to a large uncertainty in measurements of the inclusive cross section. At the Tevatron, b{bar b} quark pairs are predominantly produced through the strong interaction. In leading order QCD, the b quarks are produced back to back in phase space. Next-to-leading order contributions involving a third particle in the final state allow production of b pairs that are very close together in …
Date: June 1, 2005
Creator: Wijngaarden, Daniel A. & Nijmegen, /Radboud U.
System: The UNT Digital Library
Measurement of the Dipion Mass Spectrum in the Decay X(3872) -> J/psi pi+ pi- at the CDF II Experiment (open access)

Measurement of the Dipion Mass Spectrum in the Decay X(3872) -> J/psi pi+ pi- at the CDF II Experiment

The author presents a measurement of the dipion mass spectrum in the decay X(3872) {yields} J/{psi}{pi}{sup +}{pi}{sup -} using a 360 pb{sup -1} sample of p{bar p} collisions at {radical}s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron Collider. As a benchmark, they also extract the dipion mass distribution for {psi}(2S) {yields} J/{psi}{pi}{sup +}{pi}{sup -} decay. The X(3872) dipion mass spectrum is compared to QCD multipole expansion predictions for various charmonium states, as well as to the hypothesis X(3872) {yields} J/{psi}{rho}{sup 0}. They find that the measured spectrum is compatible with {sup 3}S{sub 1} charmonium decaying to J/{psi}{pi}{sup +}{pi}{sup -} and with the X(3872) {yields} J/{psi}{rho}{sup 0} hypothesis. There is, however, no {sup 3}S{sub 1} charmonium state available for assignment to the X(3872). The multipole expansion calculations for {sup 1}P{sub 1} and {sup 3}D{sub J} states are in clear disagreement with the X(3872) data. For the {psi}(2S) the data agrees well with previously published results and to multipole expansion calculations for {sup 3}S{sub 1} charmonium. Other, non-charmonium, models for the X(3872) are described too. They conclude that since the dipion mass spectrum for X(3872) is compatible with J/{psi}{rho}{sup 0} hypothesis, the X(3872) should be C-positive. …
Date: June 1, 2005
Creator: Rakitin, Alexander Y.
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
Nuclear Forensics Attributing the Source of Spent Fuel Used in an RDD Event (open access)

Nuclear Forensics Attributing the Source of Spent Fuel Used in an RDD Event

An RDD attack against the U.S. is something America needs to prepare against. If such an event occurs the ability to quickly identify the source of the radiological material used in an RDD would aid investigators in identifying the perpetrators. Spent fuel is one of the most dangerous possible radiological sources for an RDD. In this work, a forensics methodology was developed and implemented to attribute spent fuel to a source reactor. The specific attributes determined are the spent fuel burnup, age from discharge, reactor type, and initial fuel enrichment. It is shown that by analyzing the post-event material, these attributes can be determined with enough accuracy to be useful for investigators. The burnup can be found within a 5% accuracy, enrichment with a 2% accuracy, and age with a 10% accuracy. Reactor type can be determined if specific nuclides are measured. The methodology developed was implemented into a code call NEMASYS. NEMASYS is easy to use and it takes a minimum amount of time to learn its basic functions. It will process data within a few minutes and provide detailed information about the results and conclusions.
Date: June 1, 2005
Creator: Scott, M.R.
System: The UNT Digital Library
Computational Study and Analysis of Structural Imperfections in 1D and 2D Photonic Crystals (open access)

Computational Study and Analysis of Structural Imperfections in 1D and 2D Photonic Crystals

Dielectric reflectors that are periodic in one or two dimensions, also known as 1D and 2D photonic crystals, have been widely studied for many potential applications due to the presence of wavelength-tunable photonic bandgaps. However, the unique optical behavior of photonic crystals is based on theoretical models of perfect analogues. Little is known about the practical effects of dielectric imperfections on their technologically useful optical properties. In order to address this issue, a finite-difference time-domain (FDTD) code is employed to study the effect of three specific dielectric imperfections in 1D and 2D photonic crystals. The first imperfection investigated is dielectric interfacial roughness in quarter-wave tuned 1D photonic crystals at normal incidence. This study reveals that the reflectivity of some roughened photonic crystal configurations can change up to 50% at the center of the bandgap for RMS roughness values around 20% of the characteristic periodicity of the crystal. However, this reflectivity change can be mitigated by increasing the index contrast and/or the number of bilayers in the crystal. In order to explain these results, the homogenization approximation, which is usually applied to single rough surfaces, is applied to the quarter-wave stacks. The results of the homogenization approximation match the FDTD results …
Date: June 1, 2005
Creator: Maskaly, Karlene Rosera
System: The UNT Digital Library