The Production Cross Sections of the Weak Vector Bosons in Proton Antiproton Collisions at s**(1/2) = 1.96-TeV and a Measurement of the W Boson Decay Width (open access)

The Production Cross Sections of the Weak Vector Bosons in Proton Antiproton Collisions at s**(1/2) = 1.96-TeV and a Measurement of the W Boson Decay Width

The theory that describes the fundamental particle interactions is called the Standard Model, which is a gauge field theory that comprises the Glashow-Weinberg-Salam model [1, 2, 3] of the weak and electromagnetic interactions and quantum chromodynamics (QCD) [4, 5, 6], the theory of the strong interactions. The discovery of the W [7, 8] and Z [9, 10] bosons in 1983 by the UA1 and UA2 collaborations at the CERN p{bar p} collider provided a direct confirmation of the unification of the weak and electromagnetic interactions. Since then, many experiments have refined our understanding of the characteristics of the W and Z bosons.
Date: April 1, 2004
Creator: Varganov, Alexei Valerievich
System: The UNT Digital Library
A Search for New Physics with High Mass Tau Pairs in proton anti-proton collisions at s**(1/2) = 1.96-TeV at CDF (open access)

A Search for New Physics with High Mass Tau Pairs in proton anti-proton collisions at s**(1/2) = 1.96-TeV at CDF

We present the results of a search for new particles decaying to tau pairs using the data corresponding to an integrated luminosity of 195 pb{sup -1} collected from March 2002 to September 2003 with the CDF detector at the Tevatron. Hypothetical particles, such as Z' and MSSM Higgs bosons can potentially produce the tau pair final state. We discuss the method of tau identification, and show the signal acceptance versus new particle mass. The low-mass region, dominated by Z {yields} {tau}{tau}, is used as a control region. In the high-mass region, we expect 2.8 {+-} 0.5 events from known background sources, and observe 4 events in the data sample. Thus no significant excess is observed, and we set upper limits on the cross section times branching ratio as a function of the masses of heavy scalar and vector particles.
Date: April 1, 2005
Creator: Wan, Zong-ru
System: The UNT Digital Library
The Effect of Initial Conditions on the Nonlinear Evolution of Perturbed Interfaces Driven by Strong Blast Waves (open access)

The Effect of Initial Conditions on the Nonlinear Evolution of Perturbed Interfaces Driven by Strong Blast Waves

In core-collapse supernovae, strong blast waves drive interfaces susceptible to Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities. In addition, perturbation growth can result from material expansion in large-scale velocity gradients behind the shock front. Laser-driven experiments are designed to produce a strongly shocked interface whose evolution is a scaled version of the unstable hydrogen-helium interface in core-collapse supernovae such as SN 1987A. The ultimate goal of this research is to develop an understanding of the effect of hydrodynamic instabilities and the resulting transition to turbulence on supernovae observables that remain as yet unexplained. In this dissertation, we present a computational study of unstable systems driven by high Mach number shock and blast waves. Using multi-physics radiation hydrodynamics codes and theoretical models, we consider the late nonlinear instability evolution of single mode, few mode, and multimode interfaces. We rely primarily on 2D calculations but present recent 3D results as well. For planar multimode systems, we show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions (IC's) by allowing for memory of the initial conditions to be retained in the mix-width at all times. The loss of transverse spectral information is demonstrated, …
Date: April 27, 2004
Creator: Miles, A
System: The UNT Digital Library
Search for electroweak top quark production in the electron + jets channel in the D0 experiment at the Tevatron (open access)

Search for electroweak top quark production in the electron + jets channel in the D0 experiment at the Tevatron

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Date: April 1, 2005
Creator: Busato, Emmanuel
System: The UNT Digital Library
Character and Effective Leadership of the Knowledge Worker (open access)

Character and Effective Leadership of the Knowledge Worker

Ulrich in the forward to the Zenger and Folkman (2002) book, ''The Extraordinary Leader'', wrote about the importance of character in leadership stating, ''Everything about great leaders radiates from character. Character improves the probability of exhibiting strong interpersonal skill. Some of this perceived character is innate . . . but more is driven by the leader's self-awareness and interactions with others'' (p. ix). The purpose of this study was to explore the relationship between leadership effectiveness and character using leader-managers of knowledge workers as the subject sample. Findings indicated that character, particularly those factors associated with honesty, setting the example, and valuing and strengthening others, were what set the most effective leader-managers apart from their peers. Technical competence and self-efficacy were found to be common characteristics of the study sample as was a drive for results. Who a leader-manager is, his/her substance, was found in this study to differentiate the ''best'' leader-managers at the Lawrence Livermore National Laboratory. By their character, leader-managers establish the environment in which knowledge workers contribute and grow. As found by Pfeiffer (2000), Leaders of companies that experience smaller gaps between what they know and what they do (to turn knowledge into action), understand that their …
Date: April 20, 2005
Creator: Khoury, A E
System: The UNT Digital Library
Microcalorimetry and the transition-edge sensor (open access)

Microcalorimetry and the transition-edge sensor

Many scientific and industrial applications call for quantum-efficient high-energy-resolution microcalorimeters for the measurement of x rays. The applications driving the development of these detectors involve the measurement of faint sources of x rays in which few photons reach the detector. Interesting astrophysical applications for these microcalorimeters include the measurement of composition and temperatures of stellar atmospheres and diffuse interstellar plasmas. Other applications of microcalorimeter technology include x-ray fluorescence (XRF) measurements of industrial or scientific samples. We are attempting to develop microcalorimeters with energy resolutions of several eV because many sources (such as celestial plasmas) contain combinations of elements producing emission lines spaced only a few eV apart. Our microcalorimeters consist of a metal-film absorber (250 {micro}m x 250{micro}m x 3 {micro}m of copper) coupled to a superconducting transition-edge-sensor (TES) thermometer. This microcalorimeter demonstrated an energy resolution of 42 eV (FWHM) at 6 keV, excellent linearity, and showed no evidence of position dependent response. The response of our microcalorimeters depends both on the temperature of the microcalorimeter and on the electrical current conducted through the TES thermometer. We present a microcalorimeter model that extends previous microcalorimeter theory to include additional current dependent effects. The model makes predictions about the effects of …
Date: April 1, 2000
Creator: Lindeman, M A
System: The UNT Digital Library
Measurement of cross-section (p anti-p --> Z0) x BF (Z0 --> tau anti-tau) at s**(1/2) = 1.96-TeV using the D0 detector at the Tevatron (open access)

Measurement of cross-section (p anti-p --> Z0) x BF (Z0 --> tau anti-tau) at s**(1/2) = 1.96-TeV using the D0 detector at the Tevatron

In this thesis the first measurement of {sigma}(p{bar p}) {yields} Z{sup 0} {yields} {tau}{bar {tau}} with the D0 detector at the Tevatron is presented. The tau pair candidates are recorded by the D0 detector using p{bar p} interactions at a center-of-mass energy of 1.96 TeV. Events in which one tau decays into a muon and the other tau final state is hadronic with one charged particle are selected for this analysis. The selection criteria for the hadronic tau decay are based on the tau final state, hence for two channels of one-prong taus: single charged pion ({tau}{sub {pi}}) and rho decays ({tau}{sub {rho}}). The selection is based on simple cuts on a number of discriminating variables and the cut values have been optimized for the best cross section measurement. Of hadronic tau candidates that have been reconstructed as {tau}{sub {pi}} candidates, 0.801 {+-} 0.017 {+-} 0.066 pass the selection cut; in the case of {tau}{sub {rho}} taus, the selection efficiency is 0.676 {+-} 0.009 {+-} 0.009. Of all QCD jets that are reconstructed as hadronic tau candidates, 0.0093 {+-} 0.0002 pass the {tau}{sub {pi}} selection cuts and 0.0122 {+-} 0.0002 the {tau}{sub {rho}} cuts. The cross section has been measured …
Date: April 1, 2004
Creator: Duensing, Silke & U., /Nijmegen
System: The UNT Digital Library
Top quark pair production in proton anti-proton collisions (open access)

Top quark pair production in proton anti-proton collisions

This thesis presents a measurement of the t{bar t} cross section in the all-jets channel, measured in p{bar p} collisions at a center of mass energy of 1.96 TeV, using data collected with the D0 detector. The dataset used for this analysis has an integrated luminosity equivalent to L = 162.5 {+-} 10.6 pb{sup -1}. A t{bar t} cross section measurement is a test of the Standard Model predictions for heavy quark production, and the first step towards measurements of the mass and other properties of the top quark. The presented measurement of the cross section for the process p{bar p} {yields} t{bar t} uses the decay channel where both top quarks decay to quarks. The top quark first decays to a b quark and a W boson, and then, for this particular channel, the W boson decays hadronically. Hence, events with six energetic quarks are expected, which ideally leads to events with six jets. These so called all-jets events have a significantly larger branching fraction than other t{bar t} decay channels. The large branching fraction in the all-jets channel means that a significant sample of t{bar t} candidates can be extracted, which can subsequently be used for studies of …
Date: April 1, 2005
Creator: Blekman, Freya & /NIKHEF, Amsterdam
System: The UNT Digital Library
Spin distribution in preequilibrium reactions for 48Ti + n. (open access)

Spin distribution in preequilibrium reactions for 48Ti + n.

Cross section measurements were made of prompt {gamma}-ray production as a function of incident neutron energy on a {sup 48}Ti sample. Partial {gamma}-ray cross sections for transitions in {sup 45-48}Ti, {sup 44-48}Sc, and {sup 42-45}Ca have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction {gamma} rays were detected with the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The {gamma}-ray excitation functions were converted to partial {gamma}-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). The data are presented for neutron energies E{sub n} between 1 to 200 MeV. These results are compared with model calculations which include compound nuclear and pre-equilibrium emission. The model calculations are performed using the STAPRE reaction code for E{sub n} up to 20 MeV and the GNASH reaction code for E{sub n} up to 120 MeV. Using the GNASH reaction code the effect of the spin distribution in preequilibrium reactions has been investigated. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshbach, Kerman, …
Date: April 6, 2005
Creator: Dashdorj, D
System: The UNT Digital Library
A Study of B→c$\bar{c}$γK in the BaBar Experiment (open access)

A Study of B→c$\bar{c}$γK in the BaBar Experiment

The BABAR Collaboration is a high energy physics experiment located at the Stanford Linear Accelerator Center. The primary goal of the experiment is to study charge and parity violation in the B-meson sector, however the copious production of B mesons decaying to other final states allows for a wide-ranging physics program. In particular, one can access the charmonium system via colour-suppressed b → c decays of the type B → c$\bar{c}$K. This thesis presents a study of B →c$\bar{c}$γK decays where c$\bar{c}$ includes J/Ψ and Ψ(2S), and K includes K<sup>±</sup>, K<sub>S</sub><sup>0</sup> and K*(892). The particular emphasis is on a search for the radiative decays X(3872) → J/Ψγ and X(3872) → Ψ(2S)γ. The X(3872) state is a recently-discovered resonance of undetermined quark composition, speculatively a conventional charmonium state or exotic four-quark di-meson molecule. This research is also sensitive to the well-known radiative charmonium decays B → χ<sub>c1,2</sub>K, which are used as verification for the analysis technique. This dissertation sets the best B → χ<sub>c1</sub>K branching fraction measurements to date, and sees the first evidence for factorization-suppressed B<sup>0</sup> → χ<sub>c2</sub>}K*<sup>0</sup> decay at a level of 3.6σ. It also provides evidence for X(3872) → J/Ψγ and X(3872) → Ψ(2S)γ with 3.6σ and 3.3σ …
Date: April 1, 2009
Creator: Fulsom, Brian Gregory
System: The UNT Digital Library
Search for the neutral MSSM Higgs bosons in the ditau decay channels at CDF Run II (open access)

Search for the neutral MSSM Higgs bosons in the ditau decay channels at CDF Run II

This thesis presents the results on a search for the neutral MSSM Higgs bosons decaying to tau pairs, with least one of these taus decays leptonically. The search was performed with a sample of 1.8 fb{sup -1} of proton-antiproton collisions at {radical}s = 1.96 TeV provided by the Tevatron and collected by CDF Run II. No significant excess over the Standard Model prediction was found and a 95% confidence level exclusion limit have been set on the cross section times branching ratio as a function of the Higgs boson mass. This limit has been translated into the MSSM Higgs sector parameter plane, tan{beta} vs. M{sub A}, for the four different benchmark scenarios.
Date: April 1, 2008
Creator: Cuenca Almenar, Cristobal & /Valencia U., IFIC
System: The UNT Digital Library
Measurements of the Differential Cross Sections for the Inclusive Production of a Photon and Heavy Flavor Jet (open access)

Measurements of the Differential Cross Sections for the Inclusive Production of a Photon and Heavy Flavor Jet

This thesis presents the first measurement of the differential production cross section of a heavy flavor (bottom or charm) jet and direct photon at the Fermilab Tevatron. These measurements were performed using data recorded with the D0 detector from proton-antiproton collisions at a center of mass energy of {radical}s = 1.96 TeV. These results probe a kinematic range for the photon transverse momentum of 30 &lt; p{sub T}{sup {gamma}} &lt; 150 GeV and rapidity of |y{sup {gamma}}| &lt; 1.0 and for jet transverse momentum p{sub T}{sup jet} &gt; 15 GeV and rapidity of |y{sup jet}| &lt; 0.8. These results are compared to next-to-leading-order theoretical calculations.
Date: April 1, 2009
Creator: Duggan, Daniel
System: The UNT Digital Library
Optical galaxy cluster detection across a wide redshift range (open access)

Optical galaxy cluster detection across a wide redshift range

The past decade is one of the most exciting period in the history of physics and astronomy. The discovery of cosmic acceleration dramatically changed our understanding about the evolution and constituents of the Universe. To accommodate the new acceleration phase into our well established Big Bang cosmological scenario under the frame work of General Relativity, there must exist a very special substance that has negative pressure and make up about 73% of the total energy density in our Universe. It is called Dark Energy. For the first time people realized that the vast majority of our Universe is made of things that are totally different from the things we are made of. Therefore, one of the major endeavors in physics and astronomy in the coming years is trying to understand, if we can, the nature of dark energy. Understanding dark energy cannot be achieved from pure logic. We need empirical evidence to finally determine about what is dark energy. The better we can constrain the energy density and evolution of the dark energy, the closer we will get to the answer. There are many ways to constrain the energy density and evolution of dark energy, each of which leads to …
Date: April 1, 2009
Creator: Hao, Jiangang
System: The UNT Digital Library
Scientist-Teacher Partnerships as Professional Development: An Action Research Study (open access)

Scientist-Teacher Partnerships as Professional Development: An Action Research Study

SUBMITTED AS A DOCTORAL DISSERTATION IN COMPLETION OF REQUIREMENTS FOR THE DEGREE OF ED.D THROUGH WASHINGTON STATE UNIVERSITY. The overall purpose of this action research study was to explore the experiences of ten middle school science teachers involved in a three-year partnership program between scientists and teachers at a Department of Energy national laboratory, including the impact of the program on their professional development, and to improve the partnership program by developing a set of recommendations based on the study’s findings. This action research study relied on qualitative data including field notes recorded at the summer academies and data from two focus groups with teachers and scientists. Additionally, the participating teachers submitted written reflections in science notebooks, participated in open-ended telephone interviews that were transcribed verbatim, and wrote journal summaries to the Department of Energy at the end of the summer academy. The analysis of the data, collaboratively examined by the teachers, the scientists, and the science education specialist acting as co-researchers on the project, revealed five elements critical to the success of the professional development of science teachers. First, scientist-teacher partnerships are a unique contribution to the professional development of teachers of science that is not replicated in other …
Date: April 17, 2009
Creator: Willcuts, Meredith H.
System: The UNT Digital Library
The Pion Charge Form Factor Through Pion Electroproduction (open access)

The Pion Charge Form Factor Through Pion Electroproduction

The goal of Jefferson Lab experiment E01-004 (F?-2) was the measurement of the longitudinal and transverse cross sections via pion electroproduction from hydrogen and deuterium for the purpose of extracting the charged pion form factor using pole dominance. The data were taken at two values of Q2 (1.60 and 2.45 GeV/c)2. In order to attain full coverage in R?, charged pions were detected in parallel kinematics (along the direction of momentum transfer, q), and at ±3 degrees off the direction of momentum transfer. For each Q2 data were taken for two values of the virtual photon polarization, ?, respectively. All data were taken at a fixed center of mass energy, W=2.22 GeV. The longitudinal and transverse pieces of the cross section were separated using the Rosenbluth separation method.
Date: April 1, 2006
Creator: Horn, Tanja
System: The UNT Digital Library
On Decays of B Mesons to a Strange Meson and an Eta or Eta' Meson at Babar (open access)

On Decays of B Mesons to a Strange Meson and an Eta or Eta' Meson at Babar

We describe studies of the decays of B mesons to final states {eta}K{sup *}(892), {eta}K{sup *}{sub 0}(S-wave), {eta}K{sup *}{sub 2}(1430), and {eta}'K based on data collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collier at the Stanford Linear Accelerator Center. We measure branching fractions and charge asymmetries for the decays B {yields} {eta}K{sup *}, where K{sup *} indicates a spin 0, 1, or 2 K{pi} system, making first observations of decays to final states {eta}K{sup *0}{sub 0}(S-wave), {eta}K{sup *+}{sub 0} (S-wave), and {eta}K{sup *0}{sub 2}(1430). We measure the time-dependent CP-violation parameters S and C for the decays B{sup 0} {yields} {eta}'K{sup 0}, observing CP violation in a charmless B decay with 5{sigma} significance considering both statistical and systematic uncertainties..
Date: April 21, 2009
Creator: Hirschauer, James Francis
System: The UNT Digital Library
Measurement of Differential Cross-Sections in the ttbar -> l+jets Channel (open access)

Measurement of Differential Cross-Sections in the ttbar -> l+jets Channel

The analysis presented in this thesis focuses on kinematic distributions in the t{bar t} system and studies in detail selected differential cross sections of top quarks as well as the reconstructed t{bar t} pair, namely the top quark transverse momentum and the t{bar t} system mass. The structure of the thesis is organized as follows: first the Standard Model of the particle physics is briefly introduced in Chapter 1, with relevant aspects of electroweak and strong interactions discussed. The physics of the top quark and its properties are then outlined in Chapter 2, together with the motivation for measuring the transverse top quark momentum and other kinematic-related variables of the t{bar t} system. The concepts of present-day high energy physics collider experiments and the explicit example of Fermilab Tevatron collider and the D0 detector in Chapters 3 and 4 are followed by the description of basic detector-level objects, i.e. tracks, leptons and jets, in Chapter 5; their identification and calibration following in next chapter with the emphasis on the jet energy scale in Chapter 6 and jet identification at the D0. The analysis itself is outlined in Chapter 7 and is structured so that first the data and simulation samples …
Date: April 1, 2009
Creator: Kvita, J. & U., /Charles
System: The UNT Digital Library
Development of a Progeny Marker for Steelhead; A Thesis submitted to Oregon State University. (open access)

Development of a Progeny Marker for Steelhead; A Thesis submitted to Oregon State University.

This study was undertaken to determine if strontium chloride could be used to create a trans-generational otolith mark in steelhead (Oncorhynchus mykiss). I completed two strontium injection trials and a survey of juvenile steelhead from various steelhead hatcheries. The two trials measured Sr:Ca ratios in otoliths in response to injections and the survey measured the natural variation in Sr:Ca ratios in otoliths of juvenile hatchery steelhead in response to the natural variation. In 2003, adult female Wallowa River, Oregon O. mykiss, were captured at the hatchery and evenly divided between a control group and two treatment groups. These females received an intraperitoneal injection of 1cc/500 g of body weight of a physiologically isotonic solution (0.9% saline) containing concentrations of 0 (control), 1000, or 5000 parts per million (ppm) of strontium chloride hexahydrate (SrCl{sub 2}* 6H{sub 2}O). Females were housed in a single outdoor tank until spawned artificially, and a distinct external tag identified each female within each treatment group. In 2004, female steelhead were captured throughout the duration of the adult returns to the Umatilla River basin and injected with 0, 1000, 5000, or 20,000-ppm strontium. In both trials, progeny of fish treated with strontium had significantly higher Sr:Ca ratios …
Date: April 15, 2009
Creator: Shippentower, Gene E.
System: The UNT Digital Library
The Study and Implementation of Electrically Small Printed Antennas for an Integrated Transceiver Design (open access)

The Study and Implementation of Electrically Small Printed Antennas for an Integrated Transceiver Design

This work focuses on the design and evaluation of the inverted-F, meandering-monopole, and loop antenna geometries. These printed antennas are studied with the goal of identifying which is suitable for use in a miniaturized transceiver design and which has the ability to provide superior performance using minimal Printed Circuit Board (PCB) space. As a result, the main objective is to characterize tradeoffs and identify which antenna provides the best compromise among volume, bandwidth and efficiency. For experimentation purposes, three types of meandering-monopole antenna are examined resulting in five total antennas for the study. The performance of each antenna under study is evaluated based upon return loss, operational bandwidth, and radiation pattern characteristics. For our purposes, return loss is measured using the S11-port reflection coefficient which helps to characterize how well the small antenna is able to be efficiently fed. Operational bandwidth is measured as the frequency range over which the antenna maintains 2:1 Voltage Standing Wave Ratio (VSWR) or equivalently has 10-dB return loss. Ansoft High Frequency Structure Simulator (HFSS) is used to simulate expected resonant frequency, bandwidth, VSWR, and radiation pattern characteristics. Ansoft HFSS simulation is used to provide a good starting point for antenna design before actual prototype …
Date: April 15, 2009
Creator: Speer, Pete
System: The UNT Digital Library
Exposure-Relevant Ozone Chemistry in Occupied Spaces (open access)

Exposure-Relevant Ozone Chemistry in Occupied Spaces

Ozone, an ambient pollutant, is transformed into other airborne pollutants in the indoor environment. In this dissertation, the type and amount of byproducts that result from ozone reactions with common indoor surfaces, surface residues, and vapors were determined, pollutant concentrations were related to occupant exposure, and frameworks were developed to predict byproduct concentrations under various indoor conditions. In Chapter 2, an analysis is presented of secondary organic aerosol formation from the reaction of ozone with gas-phase, terpene-containing consumer products in small chamber experiments under conditions relevant for residential and commercial buildings. The full particle size distribution was continuously monitored, and ultrafine and fine particle concentrations were in the range of 10 to&gt;300 mu g m-3. Particle nucleation and growth dynamics were characterized.Chapter 3 presents an investigation of ozone reactions with aircraft cabin surfaces including carpet, seat fabric, plastics, and laundered and worn clothing fabric. Small chamber experiments were used to determine ozone deposition velocities, ozone reaction probabilities, byproduct emission rates, and byproduct yields for each surface category. The most commonly detected byproducts included C1?C10 saturated aldehydes and skin oil oxidation products. For all materials, emission rates were higher with ozone than without. Experimental results were used to predict byproduct exposure …
Date: April 1, 2009
Creator: Coleman, Beverly Kaye
System: The UNT Digital Library
A search for muon neutrino and antineutrino disappearance in the Booster Neutrino Beam (open access)

A search for muon neutrino and antineutrino disappearance in the Booster Neutrino Beam

This dissertation presents a search for {mu}{sub {nu}} and {bar {mu}{sub {nu}}} disappearance with the MiniBooNE experiment in the {Delta}m{sup 2} region of a few eV{sup 2}. Disappearance measurements in this oscillation region constrain sterile neutrino models and CPT violation in the lepton sector. Fits to the shape of the {mu}{sub {nu}} and {bar {mu}{sub {nu}}} energy spectra reveal no evidence for disappearance in either mode. This is the first test of {bar {mu}{sub {nu}}} disappearance between {Delta}m{sup 2} = 0:1 -- 10 eV2. In addition, prospects for performing a joint analysis using the SciBooNE detector in conjunction with MiniBooNE are discussed.
Date: April 1, 2009
Creator: Mahn, Kendall Brianna McConnel
System: The UNT Digital Library
Search for a Neutral Long-Lived Particle Decaying to B-Jets (open access)

Search for a Neutral Long-Lived Particle Decaying to B-Jets

The existence of the Higgs boson is required by the Standard Model of particle physics, yet it has not been observed. The precise nature of the Higgs boson is unknown and the mechanism by which it interacts with known Standard Model particles is also not known. Long-lived, electrically neutral hadrons have recently been proposed in hidden-valley models and could constitute a pathway through which the Higgs boson communicates with the Standard Model. Such a scenario may provide a novel path to Higgs discovery at the Tevatron. This thesis describes a search for a neutral, long-lived particle produced in decays of Higgs bosons in p{bar p} collisions at a center-of-mass energy of {radical}s = 1.96 TeV, which decays to b-jets and lives long enough to travel at least 1.6 cm before decaying. This analysis uses 3.65 fb{sup -1} of data recorded with the Run II D0 detector at the Fermilab Tevatron collider from April 2002 to August of 2008. We perform a search for eight possible hidden-valley scenarios resulting from a Higgs decay. No significant excess over background is observed and cross-section limits are placed at 95% CL.
Date: April 1, 2009
Creator: Johnson, Chad
System: The UNT Digital Library
Measurement of the inclusive isolated prompt photon production cross section at the Tevatron using the CDF detector (open access)

Measurement of the inclusive isolated prompt photon production cross section at the Tevatron using the CDF detector

In this thesis we present the measurement of the inclusive isolated prompt photon cross section with a total integrated luminosity of 2.5 fb{sup -1} of data collected with the CDF Run II detector at the Fermilab Tevatron Collider. The prompt photon cross section is a classic measurement to test perturbative QCD (pQCD) with potential to provide information on the parton distribution function (PDF), and sensitive to the presence of new physics at large photon transverse momentum. Prompt photons also constitute an irreducible background for important searches such as H {yields} {gamma}{gamma}, or SUSY and extra-dimensions with energetic photons in the final state. The Tevatron at Fermilab (Batavia, U.S.A.) is currently the hadron collider that operates at the highest energies in the world. It collides protons and antiprotons with a center-of-mass energy of 1.96 TeV. The CDF and the D0 experiments are located in two of its four interaction regions. In Run I at the Tevatron, the direct photon production cross section was measured by both CDF and DO, and first results in Run II have been presented by the DO Collaboration based on 380 pb{sup -1}. Both Run I and Run II results show agreement with the theoretical predictions except …
Date: April 1, 2009
Creator: Deluca Silberberg, Carolina
System: The UNT Digital Library
A search for particle dark matter using cryogenic germanium and silicon detectors in the one- and two- tower runs of CDMS-II at Soudan (open access)

A search for particle dark matter using cryogenic germanium and silicon detectors in the one- and two- tower runs of CDMS-II at Soudan

Images of the Bullet Cluster of galaxies in visible light, X-rays, and through gravitational lensing confirm that most of the matter in the universe is not composed of any known form of matter. The combined evidence from the dynamics of galaxies and clusters of galaxies, the cosmic microwave background, big bang nucleosynthesis, and other observations indicates that 80% of the universe's matter is dark, nearly collisionless, and cold. The identify of the dar, matter remains unknown, but weakly interacting massive particles (WIMPs) are a very good candidate. They are a natural part of many supersymmetric extensions to the standard model, and could be produced as a nonrelativistic, thermal relic in the early universe with about the right density to account for the missing mass. The dark matter of a galaxy should exist as a spherical or ellipsoidal cloud, called a 'halo' because it extends well past the edge of the visible galaxy. The Cryogenic Dark Matter Search (CDMS) seeks to directly detect interactions between WIMPs in the Milky Way's galactic dark matter halo using crystals of germanium and silicon. Our Z-sensitive ionization and phonon ('ZIP') detectors simultaneously measure both phonons and ionization produced by particle interactions. In order to find …
Date: April 1, 2008
Creator: Ogburn, Reuben Walter, IV
System: The UNT Digital Library