Electrochemical arsenic remediation for rural Bangladesh (open access)

Electrochemical arsenic remediation for rural Bangladesh

Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. In Bangladesh alone, up to 57 million people drink arsenic-laden water from shallow wells. ElectroChemical Arsenic Remediation(ECAR) overcomes many of the obstacles that plague current technologies and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis. In this work, ECAR was shown to effectively reduce 550 - 580 mu g=L arsenic (including both As[III]and As[V]in a 1:1 ratio) to below the WHO recommended maximum limit of 10 mu g=L in synthetic Bangladesh groundwater containing relevant concentrations of competitive ions such as phosphate, silicate, and bicarbonate. Arsenic removal capacity was found to be approximately constant within certain ranges of current density, but was found to change substantially between ranges. In order of decreasing arsenic removal capacity, the pattern was: 0.02 mA=cm2> 0.07 mA=cm2> 0.30 - 1.1 mA=cm2> 5.0 - 100 mA=cm2. Current processing time was found to effect arsenic removal capacity independent of either charge density or current density. Electrode polarization studies showed no passivation of the electrode in the tested range (up to current density 10 mA=cm2) and ruled out oxygen …
Date: January 1, 2009
Creator: Addy, Susan Amrose
System: The UNT Digital Library
Search for the Standard Model Higgs Boson in the Missing Transverse Energy and b-jet signature in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV (open access)

Search for the Standard Model Higgs Boson in the Missing Transverse Energy and b-jet signature in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV

We report on the results of a search for the standard model Higgs boson produced in association with a W or Z boson in p{bar p} collisions at {radical}s = 1.96 TeV recorded by the CDF II experiment at the Tevatron in a data sample corresponding to an integrated luminosity of 2.1 fb{sup -1}. We consider events having no identified charged leptons, a large imbalance in transverse momentum, and two or three jets where at least one jet contains a secondary vertex consistent with the decay of a b hadron. The main backgrounds are modeled with innovative techniques using data. The sensitivity of the search is optimized using multivariate discriminant techniques. We find good agreement between data and the standard model predictions. We place 95% confidence level upper limits on production cross section times branching ratio for several Higgs boson masses ranging from 110 GeV=c{sup 2} to 150 GeV=c{sup 2}. For a mass of 115 GeV=c{sup 2} the observed (expected) limit is 6.9 (5.6) times the standard model prediction.
Date: May 1, 2009
Creator: Apresyan, Artur
System: The UNT Digital Library
Muon neutrino disappearance at MINOS (open access)

Muon neutrino disappearance at MINOS

A strong case has been made by several experiments that neutrinos oscillate, although important questions remain as to the mechanisms and precise values of the parameters. In the standard picture, two parameters describe the nature of how the neutrinos oscillate: the mass-squared difference between states and the mixing angle. The purpose of this thesis is to use data from the MINOS experiment to precisely measure the parameters associated with oscillations first observed in studies of atmospheric neutrinos. MINOS utilizes two similar detectors to observe the oscillatory nature of neutrinos. The Near Detector, located 1 km from the source, observes the unoscillated energy spectrum while the Far Detector, located 735 km away, is positioned to see the oscillation signal. Using the data in the Near Detector, a prediction of the expected neutrino spectrum at the Far Detector assuming no oscillations is made. By comparing this prediction with the MINOS data, the atmospheric mixing parameters are measured to be {Delta}m{sub 32}{sup 2} = 2.45{sub +0.12}{sup -0.12} x 10{sub -3} eV{sup 2} and sin{sup 2}(2{theta}{sub 32}) = 1.00{sub -0.04}{sup +0.00} (> 0.90 at 90% confidence level).
Date: August 1, 2009
Creator: Armstrong, R.
System: The UNT Digital Library
Uncovering the single top: observation of electroweak top quark production (open access)

Uncovering the single top: observation of electroweak top quark production

The top quark is generally produced in quark and anti-quark pairs. However, the Standard Model also predicts the production of only one top quark which is mediated by the electroweak interaction, known as 'Single Top'. Single Top quark production is important because it provides a unique and direct way to measure the CKM matrix element V{sub tb}, and can be used to explore physics possibilities beyond the Standard Model predictions. This dissertation presents the results of the observation of Single Top using 2.3 fb{sup -1} of Data collected with the D0 detector at the Fermilab Tevatron collider. The analysis includes the Single Top muon+jets and electron+jets final states and employs Boosted Decision Tress as a method to separate the signal from the background. The resulting Single Top cross section measurement is: (1) {sigma}(p{bar p} {yields} tb + X, tqb + X) = 3.74{sub -0.74}{sup +0.95} pb, where the errors include both statistical and systematic uncertainties. The probability to measure a cross section at this value or higher in the absence of signal is p = 1.9 x 10{sup -6}. This corresponds to a standard deviation Gaussian equivalence of 4.6. When combining this result with two other analysis methods, the resulting …
Date: August 1, 2009
Creator: Benitez, Jorge Armando
System: The UNT Digital Library
Neutrino and antineutrino inclusive charged-current cross section measurement with the MINOS near detector (open access)

Neutrino and antineutrino inclusive charged-current cross section measurement with the MINOS near detector

This thesis presents the measurement of energy dependence of the neutrino-nucleon inclusive charged current cross section on an isoscalar target in the range 3-50 GeV for neutrinos and 5-50 GeV energy range for antineutrinos. The data set was collected with the MINOS Near Detector using the wide band NuMI beam at Fermilab. The size of the charged current sample is 1.94 x 10{sup 6} neutrino events and 1.60 x 10{sup 5} antineutrino events. The flux has been extracted using a low hadronic energy sub-sample of the charged current events. The energy dependence of the cross section is obtained by dividing the charged current sample with the extracted flux. The neutrino and antineutrino cross section exhibits a linear dependence on energy at high energy but shows deviations from linear behavior at low energy. We also present a measurement of the ratio of antineutrino to neutrino inclusive cross section.
Date: March 1, 2009
Creator: Bhattacharya, Debdatta & U., /Pittsburgh
System: The UNT Digital Library
Observation of excited state charge transfer with fs/ps-CARS (open access)

Observation of excited state charge transfer with fs/ps-CARS

Excited state charge transfer processes are studied using the fs/ps-CARS probe technique. This probe allows for multiplexed detection of Raman active vibrational modes. Systems studied include Michler's Ketone, Coumarin 120, 4-dimethylamino-4{prime}-nitrostilbene, and several others. The vibrational spectrum of the para di-substituted benzophenone Michler's Ketone in the first excited singlet state is studied for the first time. It is found that there are several vibrational modes indicative of structural changes of the excited molecule. A combined experimental and theoretical approach is used to study the simplest 7-amino-4-methylcoumarin, Coumarin 120. Vibrations observed in FTIR and spontaneous Raman spectra are assigned using density functional calculations and a continuum solvation model is used to predict how observed modes are affected upon inclusion of a solvent. The low frequency modes of the excited state charge transfer species 4-dimethylamino-4{prime}-nitrostilbene are studied in acetonitrile. Results are compared to previous work on this molecule in the fingerprint region. Finally, several partially completed projects and their implications are discussed. These include the two photon absorption of Coumarin 120, nanoconfinement in cyclodextrin cavities and sensitization of titania nanoparticles.
Date: August 1, 2009
Creator: Blom, Alex Jason
System: The UNT Digital Library
Measurement of electron neutrino appearance with the MINOS experiment (open access)

Measurement of electron neutrino appearance with the MINOS experiment

MINOS is a long-baseline two-detector neutrino oscillation experiment that uses a high intensity muon neutrino beam to investigate the phenomena of neutrino oscillations. By measuring the neutrino interactions in a detector near the neutrino source and again 735 km away from the production site, it is possible to probe the parameters governing neutrino oscillation. The majority of the {nu}{sub {mu}} oscillate to {nu}{sub {tau}} but a small fraction may oscillate instead to {nu}{sub e}. This thesis presents a measurement of the {nu}{sub e} appearance rate in the MINOS far detector using the first two years of exposure. Methods for constraining the far detector backgrounds using the near detector measurements is discussed and a technique for estimating the uncertainty on the background and signal selection are developed. A 1.6{sigma} excess over the expected background rate is found providing a hint of {nu}{sub e} appearance.
Date: May 1, 2009
Creator: Boehm, Joshua Adam Alpern & U., /Harvard
System: The UNT Digital Library
COUPLED MULTI-GROUP NEUTRON PHOTON TRANSPORT FOR THE SIMULATION OF HIGH-RESOLUTION GAMMA-RAY SPECTROSCOPY APPLICATIONS (open access)

COUPLED MULTI-GROUP NEUTRON PHOTON TRANSPORT FOR THE SIMULATION OF HIGH-RESOLUTION GAMMA-RAY SPECTROSCOPY APPLICATIONS

The accurate and efficient simulation of coupled neutron-photon problems is necessary for several important radiation detection applications. Examples include the detection of nuclear threats concealed in cargo containers and prompt gamma neutron activation analysis for nondestructive determination of elemental composition of unknown samples.
Date: August 1, 2009
Creator: Burns, Kimberly A.
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
Search for the Standard Model Higgs Boson in associated production with w boson at the Tevatron (open access)

Search for the Standard Model Higgs Boson in associated production with w boson at the Tevatron

A search for the Standard Model Higgs boson in proton-antiproton collisions with center-of-mass energy 1.96 TeV at the Tevatron is presented in this dissertation. The process of interest is the associated production of W boson and Higgs boson, with the W boson decaying leptonically and the Higgs boson decaying into a pair of bottom quarks. The dataset in the analysis is accumulated by the D0 detector from April 2002 to April 2008 and corresponding to an integrated luminosity of 2.7 fb{sup -1}. The events are reconstructed and selected following the criteria of an isolated lepton, missing transverse energy and two jets. The D0 Neural Network b-jet identification algorithm is further used to discriminate b jets from light jets. A multivariate analysis combining Matrix Element and Neural Network methods is explored to improve the Higgs boson signal significance. No evidence of the Higgs boson is observed in this analysis. In consequence, an observed (expected) limit on the ratio of {sigma} (p{bar p} {yields} WH) x Br (H {yields} b{bar b}) to the Standard Model prediction is set to be 6.7 (6.4) at 95% C.L. for the Higgs boson with a mass of 115 GeV.
Date: November 1, 2009
Creator: Chun, Xu
System: The UNT Digital Library
Synthesis, characterization, and application of surface-functionalized ordered mesoporous nanoparticles (open access)

Synthesis, characterization, and application of surface-functionalized ordered mesoporous nanoparticles

The dissertation begins with Chapter 1, which is a general introduction of the fundamental synthesis of mesoporous silica materials, the selective functionlization of mesoporous silica materials, and the synthesis of nanostructured porous materials via nanocasting. In Chapter 2, the thermo-responsive polymer coated mesoporous silica nanoparticles (MSN) was synthesized via surface-initated polymerization and exhibited unique partition activities in a biphasic solution with the thermally induced change. In Chapter 3, the monodispersed spherical MSN with different mesoporous structure (MCM-48) was developed and employed as a template for the synthesis of mesoporous carbon nanoparticles (MCN) via nanocasting. MCN was demonstrated for the delivery of membrane impermeable chemical agents inside the cells. The cellular uptake efficiency and biocompabtibility of MCN with human cervical cancer cells were also investigated. In addition to the biocompabtibility of MCN, MCN was demonstrated to support Rh-Mn nanoparticles for catalytic reaction in Chapter 4. Owing to the unique mesoporosity, Rh-Mn nanoparticles can be well distributed inside the mesoporous structure and exhibited interesting catalytic performance on CO hydrogenation. In Chapter 5, the synthesis route of the aforementioned MCM-48 MSN was discussed and investigated in details and other metal oxide nanoparticles were also developed via nanocasting by using MCM-48 MSN as a …
Date: January 1, 2009
Creator: Chung, Po-Wen
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>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
Surface modes at metallic an photonic crystal interfaces (open access)

Surface modes at metallic an photonic crystal interfaces

A surface mode is an electromagnetic field distribution bounded at a surface. It decays exponentially with the distance from the surface on both sides of the surface and propagates at the surface. The surface mode exists at a metal-dielectric interface as surface plasmon (1) or at a photonic crystal surface terminated properly (34; 35; 36). Besides its prominent near-filed properties, it can connect structures at its propagation surface and results in far-field effects. Extraordinary transmission (EOT) and beaming are two examples and they are the subjects I am studying in this thesis. EOT means the transmission through holes in an opaque screen can be much larger than the geometrical optics limitation. Based on our everyday experience about shadows, the transmission equals the filling ratio of the holes in geometrical optics. The conventional diffraction theory also proved that the transmission through a subwavelength circular hole in an infinitely thin perfect electric conductor (PEC) film converges to zero when the hole's dimension is much smaller than the wavelength (40). Recently it is discovered that the transmission can be much larger than the the filling ratio of the holes at some special wavelengths (41). This cannot be explained by conventional theories, so it …
Date: January 1, 2009
Creator: Dai, Weitao
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
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 < p{sub T}{sup {gamma}} < 150 GeV and rapidity of |y{sup {gamma}}| < 1.0 and for jet transverse momentum p{sub T}{sup jet} > 15 GeV and rapidity of |y{sup jet}| < 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
Construction and testing of the scintillating fibre trackers for MICE (open access)

Construction and testing of the scintillating fibre trackers for MICE

The discovery of neutrino mass through experimental evidence of neutrino oscillations at the end of the last century has provided the first proof that the Standard Model of particle physics is incomplete. To be able to extend the Standard Model to incorporate massive neutrinos first requires many theoretical uncertainties surrounding the particle and its interactions to be understood. Therefore, a dedicated experimental programme is needed over the coming decades to provide precision measurements of the neutrino oscillation parameters and also a possible measurement of CP violation in the lepton sector, which could have astrophysical consequences. An intense source of neutrinos is required to achieve these precision measurements and the leading contender proposed to provide this neutrino beam, is the Neutrino Factory. Before a Neutrino Factory facility can be realised, a number of technological challenges need to be evaluated and understood first. One of which, is reduce the large phase space volume (emittance) of the initial muon beam, which is eventually stored and through decay provides the neutrino beam. Ionisation cooling is the chosen method to achieve this and the Muon Ionisation Cooling Experiment (MICE) at Rutherford Laboratory in the UK, is required to demonstrate ionisation cooling and its feasibility for …
Date: September 1, 2009
Creator: Fish, Aron
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
Correlations in bottom quark pair production at the Fermilab Tevatron (open access)

Correlations in bottom quark pair production at the Fermilab Tevatron

I present an analysis of b{bar b} pair production correlations, using dimuon-triggered data collected with the Collider Detector at Fermilab (CDF) in p{bar p} collisions at {radical}s = 1.96 TeV during Run II of the TeVatron. The leading order (LO) and next-to-leading order (NLO) b quark production processes are discriminated by the angular and momentum correlations between the b{bar b} pair. Track-level jets containing a muon are classified by b quark content and used to estimate the momentum vector of the progenitor b quark. The theoretical distributions given by the MC{at}NLO event generator are tested against the data.
Date: January 1, 2009
Creator: Galyardt, Jason Edward
System: The UNT Digital Library
Discovery of single top quark production (open access)

Discovery of single top quark production

The top quark is by far the heaviest known fundamental particle with a mass nearing that of a gold atom. Because of this strikingly high mass, the top quark has several unique properties and might play an important role in electroweak symmetry breaking - the mechanism that gives all elementary particles mass. Creating top quarks requires access to very high energy collisions, and at present only the Tevatron collider at Fermilab is capable of reaching these energies. Until now, top quarks have only been observed produced in pairs via the strong interaction. At hadron colliders, it should also be possible to produce single top quarks via the electroweak interaction. Studies of single top quark production provide opportunities to measure the top quark spin, how top quarks mix with other quarks, and to look for new physics beyond the standard model. Because of these interesting properties, scientists have been looking for single top quarks for more than 15 years. This thesis presents the first discovery of single top quark production. An analysis is performed using 2.3 fb{sup -1} of data recorded by the D0 detector at the Fermilab Tevatron Collider at centre-of-mass energy {radical}s = 1.96 TeV. Boosted decision trees are …
Date: May 1, 2009
Creator: Gillberg, Dag
System: The UNT Digital Library
CROSS SECTION MEASUREMENTS IN THE MAIN INJECTOR PARTICLE PRODUCTION (FNAL-E907) EXPERIMENT AT 58 GEV ENERGY (open access)

CROSS SECTION MEASUREMENTS IN THE MAIN INJECTOR PARTICLE PRODUCTION (FNAL-E907) EXPERIMENT AT 58 GEV ENERGY

Cross-sections are presented for 58 GeV {pi}, K, and p on a wide range of nuclear targets. These cross-sections are essential for determining the neutrino flux in measurements of neutrino cross-sections and oscillations. The E907 Main Injector Particle Production (MIPP) experiment at Fermilab is a fixed target experiment for measuring hadronic particle production using primary 120 GeV/c protons and secondary {pi}, K, and p beams. The particle identification is made by dE/dx in a time projection chamber, and by time-of-flight, differential Cherenkov and ring imaging Cherenkov detectors, which together cover a wide range of momentum from 0.1 GeV/c up to 120 GeV/c. MIPP targets span the periodic table, from hydrogen to uranium, including beryllium and carbon. The MIPP has collected {approx} 0.26 x 10{sup 6} events of 58 GeV/c secondary particles produced by protons from the main injector striking a carbon target.
Date: December 1, 2009
Creator: Gunaydin, Yusuf Oguzhan
System: The UNT Digital Library
First evidence for WW and WZ diboson production with semi-leptonic decays at a Hadron Collider (open access)

First evidence for WW and WZ diboson production with semi-leptonic decays at a Hadron Collider

Presented is a measurement of the simultaneous production of a W{sup {+-}} boson in association with a second weak boson (W{sup {+-}} or Z{sup 0}) in p{bar p} collisions at {radical}s = 1.96 TeV. Events are consider with one electron or one muon, missing transverse energy, and at least two hadronic jets. The data were collected by the D0 detector in Run IIa of the Tevatron accelerator and correspond to 1.07 fb{sup -1} of integrated luminosity for each of the two channels (WW/WZ {yields} e{nu}q{bar q} and WW/WZ {yields} {mu}{nu}q{bar q}). The cross section for WW + WZ production is measured to be 20.2 {+-} 2.5(stat) {+-} 3.6(sys) {+-} 1.2(lum) pb with a Gaussian significance of 4.4 standard deviations above the background-only scenario. This measurement is consistent with the Standard Model prediction and represents the first direct evidence for WW and WZ production with semi-leptonic decays at a hadron collider.
Date: March 1, 2009
Creator: Haley, Joseph Glenn Biddle
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
A Study of Charged Current Single Charged Pion Productions on Carbon in a Few-GeV Neutrino Beam (open access)

A Study of Charged Current Single Charged Pion Productions on Carbon in a Few-GeV Neutrino Beam

Understanding single charged pion production via neutrino-nucleus charged current interaction in the neutrino energy region of a few GeV is essential for future neutrino oscillation experiments since this process is a dominant background for {nu}{sub {mu}} {yields} {nu}{sub x} oscillation measurements. There are two contributions to this process: single pion production via baryonic resonance ({nu}{sub {mu}}N {yields} {mu}{sup -} N{pi}{sup +}) and coherent pion production interacting with the entire nucleus ({nu}{sub {mu}}A {yields} {mu}{sup -} A{pi}{sup +}), where N is nucleon in the nucleus and A is the nucleus. The purpose of the study presented in this thesis is a precise measurement of charged current single charged pion productions, resonant and coherent pion productions, with a good final state separation in the neutrino energy region of a few GeV. In this thesis, we focus on the study of charged current coherent pion production from muon neutrinos scattering on carbon, {nu}{sub {mu}} {sup 12}C {yields} {mu}{sup -12}C{pi}{sup +}, in the SciBooNE experiment. This is motivated by the fact that without measuring this component first, the precise determination of resonant pion production cross section can not be achieved since the contribution of coherent pion production in the region of small muon scattering …
Date: January 1, 2009
Creator: Hiraide, Katsuki & U., /Kyoto
System: The UNT Digital Library
Measurements of top quark pair production cross section in proton anti-proton collisions at s**(1/2) = 1.96 TeV in the tau + jets final state using 1 inv fb of data (open access)

Measurements of top quark pair production cross section in proton anti-proton collisions at s**(1/2) = 1.96 TeV in the tau + jets final state using 1 inv fb of data

This dissertation presents a new measurement of p{bar p} {yields} t{bar t}X production at {radical}s = 1.96 TeV using 974.2 pb{sup -1} of data collected with the D0 detector between 2002 and 2006. We focus on the final state where the W boson from one of the top quarks decays into a {tau} lepton and its associated neutrino, while the other W boson decays into a quark-antiquark pair. We aim to select those events in which the {tau} lepton subsequently decays hadronically, meaning to one or three charged hadrons, zero or more neutral hadrons and a tau neutrino (the charge conjugate processes are implied in all of the above). The observable signature thus consists of a narrow calorimeter shower with associated track(s) characteristic of a hadronic tau decay, four or more jets, of which two are initiated by b quarks accompanying the W's in the top quark decays, and a large net missing momentum in the transverse plane due to the energetic neutrino-antineutrino pair that leave no trace in the detector media. The preliminary result for the measured cross section is: {sigma}(t{bar t}) = 6.9{sub -1.2}{sup +1.2}(stat){sub -0.7}{sup +0.8}(syst) {+-} 0.4 (lumi) pb. This indicates that our finding is consistent …
Date: December 1, 2009
Creator: Hossain, Sohrab
System: The UNT Digital Library