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A measurement of the t anti-t production cross-section in proton anti-proton collisions at s**(1/2) = 1.96-TeV with the D0 detector at the Tevatron using final states with a muon and jets
A preliminary measurement of the t{bar t} production cross section at {radical}s = 1.96 TeV is presented. The {mu}-plus-jets final state is analyzed in a data sample of 94 pb{sup -1} and a total of 14 events are selected with a background expectation of 11.7 {+-} 1.9 events. The measurement yields: {sigma}{sub p{bar p} {yields} t{bar t} + X} = 2.4{sub -3.5}{sup +4.2}(stat.){sub -2.6}{sup +2.5}(syst.) {+-} 0.3(lumi.) pb. The analysis, being part of a larger effort to re-observe the top quark in Tevatron Run II data and to measure the production cross section, is combined with results from all available analyses channels. The combined result yields: {sigma}{sub p{bar p}} {yields} t{bar t} + X = 8.1{sub -2.0}{sup +2.2}(stat.){sub -1.4}{sup +1.6}(syst.) {+-} 0.8(lumi.) pb.
Date:
February 1, 2004
Creator:
Klute, Markus
System:
The UNT Digital Library
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
Experimental and Numerical Investigation of the Role of Initial Condition of the Dynamics of Rayleigh-Taylor Mixing
Experiments and direct numerical simulations have been performed to examine the effects of initial conditions on the dynamics of a Rayleigh-Taylor mixing layer. Experiments were performed on a water channel facility to quantify the interfacial and velocity perturbations initially present at the two-fluid interface in a small Atwood number mixing layer. The measurements have been parameterized for implementation in numerical simulations of the experiment, and two- and three-dimensional direct numerical simulations (DNS) of the experiment have been performed. It is shown that simulations implemented with initial velocity perturbations are required to match experimentally-measured statistics. Data acquired from both the experiment and numerical simulations are used to elucidate the role of initial conditions on the evolution of integral-scale, turbulence, and mixing statistics. Early-time turbulence and mixing statistics will be shown to be strongly dependent upon the early-time transition of the initial perturbation from a weakly- to a strongly-nonlinear flow.
Date:
August 16, 2004
Creator:
Mueschke, N
System:
The UNT Digital Library
Search for first-generation leptoquarks in the jets and missing transverse energy topology in proton-antiproton collisions at center-of-mass energy 1.96 TeV
The authors performed a search for the pair production of first-generation leptoquarks using 191 pb{sup -1} of proton-antiproton collision data recorded by the CDF experiment during Run II of the Tevatron. The leptoquarks are sought via their decay into a neutrino and quark, which yields missing transverse energy and several high-E{sub T} jets. Several control regions were studied to check the background estimation from Standard Model sources, with good agreement observed in data. In the leptoquark signal region, 124 events were observed with 118.3 {+-} 14.5 expected from background. Therefore, no evidence for leptoquark production was observed, and limits were set on the cross section times the squared branching ratio. Using the next-to-leading order cross section for leptoquark production, they excluded the mass interval 78 to 117 GeV/c{sup 2} at the 95% confidence level for 100% branching ratio into neutrino plus quark.
Date:
March 1, 2004
Creator:
Tsybychev, Dmitri
System:
The UNT Digital Library
Measurement of the top pair production cross section at CDF using neural networks
In the Tevatron accelerator at Fermilab protons and antiprotons are collided at a 1.96 TeV center of mass energy. CDF and D0 are the two experiments currently operating at the Tevatron. At these energies top quark is mostly produced via strong interactions as a top anti-top pair (t{bar t}). The top quark has an extremely short lifetime and according to the Standard Model it decays with {approx} 100% probability into a b quark and a W boson. In the ''lepton+jets'' channel, the signal from top pair production is detected for those events where one of the two W bosons decays hadronically in two quarks which we see as jets in the detector, and the other W decays into an electrically charged lepton and a neutrino. A relatively unambiguous identification in the detector is possible when we require that the charged lepton must be an electron or muon of either charge. The neutrino does not interact in the detector and its presence is inferred from an imbalance in the transverse energy of the event. They present a measurement of the top pair production cross section in p{bar p} collisions at 1.96 TeV, from a data sample collected at CDF between March …
Date:
November 1, 2004
Creator:
Marginean, Radu
System:
The UNT Digital Library
Search for Gauge Mediated Supersymmetry in the gamma gamma missing ET Channel
We present results on a search for Gauge Mediated Supersymmetry in the di-photon final state using Run II data collected by the D0 Experiment at the Fermilab Tevatron Collider. We discuss event selection, Standard Model backgrounds, and the lower limits on the lightest neutralino and chargino masses resulted from this analysis.
Date:
December 1, 2004
Creator:
Kesisoglou, Stilianos Isaak & U., /Brown
System:
The UNT Digital Library
Mass spectrum analysis of K- pi+ from the semileptonic decay D+ --> K- pi+ mu+ nu
The Higgs mechanism preserves the gauge symmetries of the Standard Model while giving masses to the W, Z bosons. Supersymmetry, which protects the Higgs boson mass scale from quantum corrections, predicts at least 5 Higgs bosons, none of which has been directly observed. This thesis presents a search for neutral Higgs bosons, produced in association with bottom quarks. The production rate is greatly enhanced at large values of the Supersymmetric parameter tan {beta}. High-energy p{bar p} collision data, collected from Run II of the Fermilab Tevatron using the D0 detector, are analyzed. In the absence of a signal, values of tan {beta} > 80-120 are excluded at 95% Confidence Level (C.L.), depending on the (CP-odd) neutral Higgs boson mass (studied from 100 to 150 GeV/c{sup 2}).
Date:
March 1, 2004
Creator:
Massafferri Rodrigues, Andre & /Rio de Janeiro, CBPF
System:
The UNT Digital Library
Measurement of the W + gamma Production in Proton - Anti-proton Collisions at s**(1/2) = 1.96-TeV
The authors present a measurement of the {bar p}p {yields} W{gamma} + X {yields} e{nu}{gamma} + X production cross section using data form the Collider Detector at Fermilab. The p{bar p} collisions were provided by the Tevatron Collider at a center of mass energy of 1.96 TeV. Electroweak theory includes the trilinear vector boson coupling, WW{gamma}, which contributes to the e{nu}{gamma} final state. The electron decay channel of the W provides a clean sample to study the production of diboson pairs. The measurement of the production cross section tests the structure of the non-Abelian character of Electroweak theory.
Date:
October 1, 2004
Creator:
Kirby, Michael H. & U., /Duke
System:
The UNT Digital Library
A Measurement of the production cross section of top-antitop pairs in proton-antiproton collisions at a center of mass of 1.96 TeV using secondary vertex b-tagging.
A measurement of the t{bar t} pair production cross section is presented using 162 pb{sup -1} of data collected by the CDF experiment during Run II at the Tevatron. t{bar t} events in the lepton+jets channel are isolated by identifying electrons and muons, reconstructing jets and transverse missing energy, and identifying b jets with a secondary vertex tagging algorithm. The efficiency of the algorithm is measured in a control sample using a novel technique that is less dependent on the simulation. For a top quark mass of 175 GeV/c{sup 2}, a cross section of {sigma}{sub t{bar t}} = 5.6{sub -1.1}{sup +1.2}(stat.){sub -0.6}{sup +0.9}(syst.)pb is measured.
Date:
December 1, 2004
Creator:
Bachacou, Henri
System:
The UNT Digital Library
Measurement of the t anti-t production cross-section at s**(1/2) = 1.96-TeV using lifetime tagging
A measurement of the t{bar t} production cross section in the lepton+jets channels with the D0 detector at {radical}s = 1.96 TeV using the lifetime-tagging techniques is presented. The t{bar t} cross section is estimated from the combination of the e+jets and {mu}+jets channels. The obtained result {sigma}{sub t{bar t}} = 7.47{sub -1.14}{sup +1.22}(stat){sub -1.03}{sup +1.65}(syst) {+-} 0.49(lumi) pb is consistent with the Standard Model expectation.
Date:
July 1, 2004
Creator:
Khanov, Alexander
System:
The UNT Digital Library
A Measurement of the Mass of the Top Quark in Lepton + Jets Events at CDF
This document presents a measurement of the top quark mass using the CDF run II detector at Fermilab. Colliding beams of protons and anti-protons at Fermilab's Tevatron ({radical}s = 1.96 TeV) produce top/anti-top pairs, which decay to W{sup +}W{sup -} b{bar b}; events are selected where one W decays hadronically, and one W decays to either e or {mu} plus a neutrino. The data sample was collected between March 2002 and September 2003, and corresponds to an integrated luminosity of approximately 162 pb{sup -1}. Thirty-seven candidate t{bar t} events are found with at least one b jet identified by its displaced vertex. In each event, the best fit top quark invariant mass is determined by minimizing a {chi}{sup 2} for the overconstrained kinematic system. A likelihood fit of the reconstructed masses in the data sample to distributions from simulated signal and background events gives a top mass of 174.9{sub -7.7}{sup +7.1}(stat.) {+-} 6.5(syst.) GeV/c{sup 2}. The dominant systematic error is due to uncertainties in the jet energy measurements.
Date:
December 1, 2004
Creator:
Brubaker, Erik Matthews
System:
The UNT Digital Library
Search for leptoquarks in jet topolgy with missing transverse energy using the D0 detector
The D0 experiment, located at the Fermilab National Accelerator Laboratory in the US, is used to study proton-anti-proton collisions at a center of mass energy of 1.96 TeV. The experiment's data acquisition system is based on a sophisticated trigger system used to select potentially interesting events. The Level 2 Silicon Track Trigger (L2STT) is part of the trigger system that provides precise reconstruction of charged particle tracks allowing the selection of events that contain the decays of long lived particles. For example, such particles appear in the decay of the Higgs boson into a pair of bottom quarks. The design of the L2STT preprocessor has greatly benefited from recent advances in electronics technology. The preprocessor has been recently installed and will be used to further optimize the triggering strategy of the experiment. Leptoquarks would mediate hypothetical new interactions between the quarks and leptons of the Standard Model. The existence of such particles would be evidence for physics beyond that model. In this thesis, a direct search for leptoquarks is performed in the jets and missing transverse energy final state. For this analysis, a trigger had to be developed along with a tool to precisely determine its efficiency. An analysis of …
Date:
October 1, 2004
Creator:
Zabi, Alexandre
System:
The UNT Digital Library
BioAerosol Mass Spectrometry: Reagentless Detection of Individual Airborne Spores and Other Bioagent Particles Based on Laser Desorption/Ionization Mass Spectrometry
Better devices are needed for the detection of aerosolized biological warfare agents. Advances in the ongoing development of one such device, the BioAerosol Mass Spectrometry (BAMS) system, are described here in detail. The system samples individual, micrometer-sized particles directly from the air and analyzes them in real-time without sample preparation or use of reagents. At the core of the BAMS system is a dual-polarity, single-particle mass spectrometer with a laser based desorption and ionization (DI) system. The mass spectra produced by early proof-of-concept instruments were highly variable and contained limited information to differentiate certain types of similar biological particles. The investigation of this variability and subsequent changes to the DI laser system are described. The modifications have reduced the observed variability and thereby increased the usable information content in the spectra. These improvements would have little value without software to analyze and identify the mass spectra. Important improvements have been made to the algorithms that initially processed and analyzed the data. Single particles can be identified with an impressive level of accuracy, but to obtain significant reductions in the overall false alarm rate of the BAMS instrument, alarm decisions must be made dynamically on the basis of multiple analyzed particles. …
Date:
July 20, 2004
Creator:
Steele, P T
System:
The UNT Digital Library
Studies of Upsilon(1S) bottomonium state production at the Tevatron Collider Experiment D0
The production of heavy quarkonium in hadronic collisions provides an ideal testing ground for our understanding of the production mechanisms for heavy quarks and the non-perturbative QCD effects that bind the quark pairs into quarkonium. In this analysis, the inclusive production cross section of the {Upsilon}(1S) bottomonium state is measured using the {Upsilon}(1S) {yields} {mu}{sup +}{mu}{sup -} decay mode. The data sample corresponds to an integrated luminosity of 159.1 {+-} 10.3 pb{sup -1}. We determine differential cross sections as functions of the {Upsilon}(1S) transverse momentum, p{sub T}{sup {Upsilon}}, for three ranges of the {Upsilon}(1S) rapidity: 0 < |y{sup {Upsilon}}| < 0.6,0.6 < |y{sup {Upsilon}}| < 1.2 and 1.2 < |y{sup {Upsilon}}| < 1.8. The shapes of d{sigma}/d{sub p{sub T}} cross sections show little variation with rapidity and are consistent with the published Run I CDF measurement over the rapidity range |y{sup {Upsilon}}| < 0.4.
Date:
November 1, 2004
Creator:
Huang, Jundong
System:
The UNT Digital Library
Search for Supersymmetric Particles in the dimuon channels
None
Date:
July 1, 2004
Creator:
Vu Anh, Tuan & /Orsay
System:
The UNT Digital Library
Search for Scalar Bottom Quarks from Gluino Decays in Proton - Anti-proton Collisions at a Center-of-Mass Energy of 1.96-TeV
The authors have performed a search for the scalar bottom quark ({tilde b}{sub 1}) from gluino ({tilde g}) decays in an R-parity conserving SUSY scenario with m{sub {tilde g}} > m{sub {tilde b}{sub 1}}, by investigating a final state of large missing transverse energy, with three or more jets, and some of them from the hadronization of b-quarks. A data sample of 156 pb{sup -1} collected by the Collider Detector at Fermilab at a center-of-mass energy of {radical}s = 1.96 TeV was used. For the final selection, jets containing secondary displaced vertices were required. This analysis has been performed ''blind'', in that the inspection of the signal region was only made after the Standard Model prediction was finalized. Comparing data with SUSY predictions, they can exclude masses of the gluino and sbottom of up to 280 and 240 GeV/c{sup 2} respectively.
Date:
December 1, 2004
Creator:
Rott, Carsten
System:
The UNT Digital Library
The b Quark Fragmentation Function, From LEP to TeVatron
The b quark fragmentation distribution has been measured, using data registered by the DELPHI experiment at the Z pole, in the years 1994-1995. The measurement made use of 176000 inclusively reconstructed B meson candidates. The errors of this measurement are dominated by systematic effects, the principal ones being related to the energy calibration. The distribution has been established in a nine bin histogram. Its mean value has been found to be <x{sub E}> = 0.704 {+-} 0.001(stat.) {+-} 0.008(syst.). Using this measurement, and other available analyses of the b-quark fragmentation distribution in e{sup +}e{sup -} collisions, the non-perturbative QCD component of the distribution has been extracted independently of any hadronic physics modeling. This distribution depends only on the way the perturbative QCD component has been defined. When the perturbative QCD component is taken from a parton shower Monte-Carlo, the non-perturbative QCD component is rather similar with those obtained from the Lund or Bowler models. When the perturbative QCD component is the result of an analytic NLL computation, the non-perturbative QCD component has to be extended in a non-physical region and thus cannot be described by any hadronic modeling. In the two examples, used to characterize these two situations, which are …
Date:
December 1, 2004
Creator:
Ben-haim, Eli
System:
The UNT Digital Library
Structural and Functional Studies of the Protamine 2-Zinc Complex from Syrian Gold Hamster (Mesocricetus Auratus) Spermatids and Sperm
The research described in this dissertation consists of four major areas: (1) sequence analysis of protamine 2 from Muroid rodents to identify potential zinc-binding domain(s) of protamine 2; (2) structural studies of the protamine 2-zinc complex from Syrian Gold hamster sperm and spermatids to elucidate the role of zinc during spermiogenesis; (3) structural studies of an unique protamine 2-zinc complex from chinchilla sperm; and (4) Nuclear Magnetic Resonance (NMR) studies of soluble complexes of hairpin oligonucleotides with synthetic arginine-rich peptides or protamine 1 isolated from bull sperm. First, zinc was quantitated in spermatids and sperm by Proton-Induced X-ray Emission (PIXE) to determine whether zinc is present in the early stages of spermiogenesis. The PIXE results revealed the zinc content varies proportionately with the amount of protamine 2 in both spermatid and sperm nuclei. An exception was chinchilla sperm containing twice the amount of protamine 2 than zinc. Further analyses by PIXE and X-ray Absorption Spectroscopy (XAS) of zinc bound to protamines isolated from hamster sperm confirmed the majority of the zinc is bound to protamine and identified the zinc ligands of protamine 2 in hamster spermatids and sperm in vivo. These studies established that zinc is bound to the protamine …
Date:
August 30, 2004
Creator:
Dolan, C E
System:
The UNT Digital Library
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
Neutrino - Induced Muons in the MINOS Far Detector
None
Date:
August 1, 2004
Creator:
Rebel, Brian J.
System:
The UNT Digital Library
Measurement of W Boson Polarization in Top Quark Decay
A measurement of the polarization of the W boson from top quark decay is an excellent test of the V-A form of the charged-current weak interaction in the standard model. Since the longitudinal W boson is intimately related to the electroweak symmetry breaking mechanism, and the standard model gives a specific prediction for the fraction of longitudinal W bosons from top decays, it is of particular interest for study. This thesis presents a measurement of W boson polarization in top quark decays through an analysis of the cos{theta}* distribution in the lepton-plus-jets channel of t{bar t} candidate events from p{bar p} collisions at {radical}s = 1.96 TeV. This measurement uses an integrated luminosity of {approx} 162 pb{sup -1} of data collected with the CDF Run II detector, resulting in 31 t{bar t} candidate events with at least one identified b jet. Using a binned likelihood fit to the cos{theta}* distribution from the t{bar t} candidate events found in this sample, the fraction of W bosons with longitudinal polarization is determined to be F{sub 0} = 0.99{sub -0.35}{sup +0.29}(stat.) {+-} 0.19(syst.), F{sub 0} > 0.33 {at} 95% CL. This result is consistent with the standard model prediction, given a top quark …
Date:
November 1, 2004
Creator:
Vickey, Trevor Neil
System:
The UNT Digital Library
Analysis of the Semileptonic Decay D0 --> anti-K0 pi- mu+ nu
This thesis describes the analysis of the semileptonic decay D{sup 0} {yields} {bar K}{sup 0} {pi}{sup -} {mu}{sup +}{nu} using FOCUS data. FOCUS is a fixed target experiment at Fermilab that studies the physics of the charm quark. Particles containing charm are produced by photon-gluon fusion from the collision of a photon beam on a BeO target. The experiment is characterized by excellent vertex resolution and particle identification. The spectrometer consists of three systems for track reconstruction (two silicon systems and one multiwire proportional chamber system) and two magnets of opposite polarity. The polarity of the magnet is such that the events of e{sup +}e{sup -} pairs produced in the target (which constitutes the main background) travel through a central opening in the detectors without interactions. Particle momentum is measured from the deflection angle in the magnets. Three multicell Cerenkov counters are used for charged particle identification (for e, {pi}, K, and p). Two different tracking systems located after several interaction lengths of shielding material are used for muon identification. The energy of neutral pions and electrons is measured in two electromagnetic calorimeters, while an hadron calorimeter is used for measuring the neutron energy. During the last four years the …
Date:
November 1, 2004
Creator:
Segoni, Ilaria Maria Lucia
System:
The UNT Digital Library
Characterization of Functionalized Self-Assembled Monolayers and Surface-Attached Interlocking Molecules Using Near-Edge X-ray Absorption Fine Structure Spectroscopy
Quantitative knowledge of the fundamental structure and substrate binding, as well as the direct measurement of conformational changes, are essential to the development of self-assembled monolayers (SAMs) and surface-attached interlocking molecules, catenanes and rotaxanes. These monolayers are vital to development of nano-mechanical, molecular electronic, and biological/chemical sensor applications. This dissertation investigates properties of functionalized SAMs in sulfur-gold based adsorbed molecular monolayers using quantitative spectroscopic techniques including near-edge x-ray absorption fine structure spectroscopy (NEXAFS) and x-ray photoelectron spectroscopy (XPS). The stability of the gold-thiolate interface is addressed. A simple model SAM consisting of dodecanethiol adsorbed on Au(111) degrades significantly in less than 24 hours under ambient laboratory air. S 2p and O 1s XPS show the gold-bound thiolates oxidize to sulfinates and sulfonates. A reduction of organic material on the surface and a decrease in order are observed as the layer degrades. The effect of the carboxyl vs. carboxylate functionalization on SAM structure is investigated. Carboxyl-terminated layers consisting of long alkyl-chain thiols vs. thioctic acid with short, sterically separated, alkyl groups are compared and contrasted. NEXAFS shows a conformational change, or chemical switchability, with carboxyl groups tilted over and carboxylate endgroups more upright. Surface-attached loops and simple surface-attached rotaxanes are quantitatively …
Date:
March 24, 2004
Creator:
Willey, T & Willey, T
System:
The UNT Digital Library
Searches for New Physics Using High Mass Dimuons at the CDF II Experiment
This work describes the measurement of inclusive jets cross section in the D0 experiment. This cross section is computed as a function of jet transverse momentum, in several rapidity intervals. This quantity is sensitive to the proton structure and is crucial for the determination of parton distribution functions (PDF), essentially for the gluon at high proton momentum fraction. The measurement presented here gives the first values obtained for Tevatron Run II for the cross section in several rapidity intervals, for an integrated luminosity of 143 pb{sup -1}. The results are in agreement, within the uncertainties, with theoretical Standard Model predictions, showing no evidence for new physics. This work points out the aspects of the detector which need better understanding to reach Run I precision and to constrain the PDFs.
Date:
December 1, 2004
Creator:
Karagoz Unel, Muge
System:
The UNT Digital Library