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Determination of the strong coupling constant ({alpha}{sub s}) and a test of perturbative QCD using W + jets processes in the D0 detector (open access)

Determination of the strong coupling constant ({alpha}{sub s}) and a test of perturbative QCD using W + jets processes in the D0 detector

The D0 experiment has accumulated data for a study of inclusive W production corresponding to a total integrated luminosity of 14.3 {plus_minus} 1.7 pb{sup {minus}1} during the 1992--1993 Fermilab Tevatron collider run. The total number of W {yields} e + {nu} candidates is 9770. The ratio of the number of W + 1 jet events to that of W + 0 jet events has been measured as a function of jet minimum E{sub T}. Using this ratio the strong coupling constant, {alpha}{sub s} at Q{sup 2} = M{sub W}{sup 2} is measured to be {alpha}{sub s}(M{sub W}{sup 2}) = 0.124 {plus_minus} 0.005(stat) {plus_minus} 0.006(MC) {plus_minus} 0.008(theory){sub {minus}0.022}{sup +0.026}(sys) or ({sub {minus}0.025}{sup +0.028} combined) with a jet minimum E{sub T} of 25 GeV. A quantitative test of perturbative QCD has been made by comparing the experimentally measured ratio with the theoretical predictions. The theoretical predictions of the ratio in both the leading order and next-to-leading order are in good agreement with the measured ratio.
Date: August 1, 1993
Creator: Yu, Jaehoon
System: The UNT Digital Library
Measurement of HO{sub x}{center_dot} production rate due to radon decay in air (open access)

Measurement of HO{sub x}{center_dot} production rate due to radon decay in air

Radon in indoor air may cause the exposure of the public to excessive radioactivity. Radiolysis of water vapor in indoor air due to radon decay could produce ({center_dot}OH and HO{sub 2} {center_dot}) that may convert atmospheric constituents to compounds of lower vapor pressure. These lower vapor pressure compounds might then nucleate to form new particles in the indoor atmosphere. Chemical amplification was used to determine HO{sub x}{center_dot} production rate in indoor air caused by radon decay. Average HO{sub x}{center_dot} production rate was found to be (4.31{plus_minus}0.07) {times} 10{sup 5} HO{sub x}{center_dot} per Rn decay per second (Bq) 3.4 to 55.0% at 22C. This work provided G{sub (HO{sub x}{center_dot})}-value, 7.86{plus_minus}0.13 No./100 eV in air by directly measuring [HO{sub x}{center_dot}] formed from the radiolysis procedure. This G value implies that HO{sub x}{center_dot} produced by radon decay in air might be formed by multiple processes and may be result of positive ion-molecule reactions, primary radiolysis, and radical reactions. There is no obvious relation between HO{sub x}{center_dot} production rate and relative humidity. A laser-induced fluorescence (LIF) system has been used for {center_dot}OH production rate measurement; it consists of an excimer laser, a dye laser, a frequency doubler, a gaseous fluorescence chamber, and other optical …
Date: August 1, 1993
Creator: Ding, Huiling
System: The UNT Digital Library
Electrons in the D0 central calorimeter: A study of the systematic biases in the measurement of the W mass (open access)

Electrons in the D0 central calorimeter: A study of the systematic biases in the measurement of the W mass

The D0 detector at Fermilab is a general purpose collider detector designed for the study of proton-antiproton collisions at a center of mass energy of 1.8 TeV. The detector consists of an inner tracking volume, a hermetic uranium/liquid argon calorimeter, and an outer muon detection system. Since the detector lacks a central magnetic field, it relies on energy measurements from the calorimeter as opposed to momentum measurements using the tracking chambers. To provide the necessary understanding of the calorimeter, a testbeam was conducted at Fermilab during the second half of 1991 featuring detector modules from the central calorimeter. Detailed simulations of the detector apparatus were also written. This thesis will present the results of this testbeam and simulation effort and relate them to the measurement of the W{sup {plus_minus}} intermediate vector boson mass in the full D0 detector. In the testbeam, an energy resolution that scaled as 14% divided by the square root of the beam energy was found. The uniformity of response of the detector as a function of angle of incidence was investigated. We found that the response increased by 4% over the range investigated. The results were compared to a simulation written using the CERN package GEANT. …
Date: August 1, 1993
Creator: Heuring, T. C.
System: The UNT Digital Library
Microwave interferometry of laser induced air plasmas formed by short laser pulses (open access)

Microwave interferometry of laser induced air plasmas formed by short laser pulses

Applications for the interaction of laser induced plasmas with electromagnetic probes requires time varying complex conductivity data for specific laser/electromagnetic probe geometries. Applications for this data include plasma switching (Q switching) and the study of ionization fronts. The plasmas were created in laboratory air by 100 ps laser pulses at a wavelength of 1 {mu}m. A long focal length lens focused the laser pulse into WR90 (X band) rectangular waveguide. Two different laser beam/electromagnetic probe geometries were investigated. For the longitudinal geometry, the laser pulse and the microwave counterpropagated inside the waveguide. For the transverse geometry, the laser created a plasma ``post`` inside the waveguide. The effects of the laser beam deliberately hitting the waveguide were also investigated. Each geometry exhibits its own characteristics. This research project focused on the longitudinal geometry. Since the laser beam intensity varies inside the waveguide, the charge distribution inside the waveguide also varies. A 10 GHz CW microwave probe traveled through the laser induced plasma. From the magnitude and phase of the microwave probe, a spatially integrated complex conductivity was calculated. No measurements of the temporal or spatial variation of the laser induced plasma were made. For the ``plasma post,`` the electron density is …
Date: August 1, 1993
Creator: Jungwirth, P. W.
System: The UNT Digital Library
Measurement of the Inclusive B-Lifetime Using $\rm {J/\psi}$'s at the CDF Experiment (open access)

Measurement of the Inclusive B-Lifetime Using $\rm {J/\psi}$'s at the CDF Experiment

This dissertation describes the measurement of the average B hadron lifetime using a high statistics sample of B → J/ΨX decays produced in p$\bar{p}$ collisions at a center of mass energy of √s = 1.8 TeV at the Fermilab Tevatron. The integrated luminosity of the sample is 10.1 pb<sup>-1</sup> recorded with the Collider Detector at Fermilab (CDF). In this analysis the decay vertex of the decay J/Ψ → μ<sup>+</sup>μ<sup>-</sup> as reconstructed by a silicon vertex detector is used to extract the lifetime from the data. This measurement is the average over all b-hadrons produced weighted by the product of their branching ratios into J/Ψ and their production cross sections. We find the following value for the average b hadron lifetime: τ<sub>B</sub> = 1.46 ± 0.06(stat.) ± 0.06(syst.) ps. This is the first measurement of the b-hadron lifetime at a hadron collider. It demonstrates that it is possible to access the large b-quark production cross section in p$\bar{p}$ collisions and to achieve high statistics even in modes which have small product branching ratios as in this case: BR(B → J/ΨX) • BR(J/Ψ → μ<sup>+</sup>μ<sup>-</sup>) = 7.7 x 10<sup>-4</sup>.
Date: August 1, 1993
Creator: Wenzel, Hans-Joachim
System: The UNT Digital Library
Synthesis, characterization, phase diagrams and superconducting and normal state magnetic properties of La{sub 2{minus}x}Sr{sub x}CuO{sub 4} (0 {le} x {le} 0.08) and electrochemically oxidized La{sub 2{minus}x}Sr{sub x}CuO{sub 4+{delta}} (0 {le} x {le} 0.33, 0 {le} {delta} {le} 0.12) (open access)

Synthesis, characterization, phase diagrams and superconducting and normal state magnetic properties of La{sub 2{minus}x}Sr{sub x}CuO{sub 4} (0 {le} x {le} 0.08) and electrochemically oxidized La{sub 2{minus}x}Sr{sub x}CuO{sub 4+{delta}} (0 {le} x {le} 0.33, 0 {le} {delta} {le} 0.12)

La{sub 2{minus}x}Sr{sub x}CuO{sub 4} (0 {le} x {le} 0.15) can all be intercalated with oxygen by a novel electrochemical oxidation method. Bulk superconductivity is found with an onset {Tc} {approx} 40 K for the whole range 0.01 {le} x {le} 0.15; for x = 0.25 and 0.33, the electrochemical oxidation did not improve the superconducting properties. The magnetic susceptibility {chi}(T = 50--320 K) data for La{sub 2}CuO{sub 4.11} and La{sub 1.92}Sr{sub 0.08}CuO{sub 4.07} are nearly identical with those of conventionally prepared La{sub 1.85}Sr{sub 0.15}CuO{sub 4}, indicating that the hole doping level (p) in the CuO{sub 2} planes of the three compounds is nearly the same. Combined thermogravimetric analysis and iodometric titration experiments indicate that part of the intercalated oxygen has a formal valence close to {minus}1. The maximum doped-hole concentration in the CuO{sub 2} planes that can be achieved from combined Sr-doping and electrochemical oxygen doping for 0 {le} x {le} 0.15 is p {approx} 0.16 holes/formula unit. Oxygen can also intercalate into single crystal La{sub 2}CuO{sub 4} through a slow electrochemical oxidation process. The required low current and long time for the charging process reflects that the oxygen intercalation for a single crystal is limited by its small specific …
Date: August 1, 1993
Creator: Chou, F.
System: The UNT Digital Library
Recovery of carboxylic acids at pH greater than pK{sub a} (open access)

Recovery of carboxylic acids at pH greater than pK{sub a}

Economics of producing carboxylic acids by fermentation is often dominated, not by the fermentation cost, but by the cost of recovering and purifying the acids from dilute aqueous solutions. Experiments were performed to measure uptakes of lactic and succinic acids as functions of pH by basic polymeric sorbents; sorbent regeneration was also tested. Performance at pH > pK{sub a} and regenerability depend on sorbent basicity; apparent pK{sub a} and monomer pK{sub a} can be used to predict sorbent performance. Two basic amine extractants, Alamine 336 and Amberlite LA-2, in were also studied; they are able to sustain capacity to higher pH in diluents that stabilize the acid-amine complex through H bonding. Secondary amines perform better than tert-amines in diluents that solvate the additional proton. Competitive sulfate and phosphate, an interference in fermentation, are taken up by sorbents more strongly than by extractants. The third step in the proposed fermentation process, the cracking of the trimethylammonium (TMA) carboxylate, was also examined. Because lactic acid is more soluble and tends to self-esterify, simple thermal cracking does not remove all TMA; a more promising approach is to esterify the TMA lactate by reaction with an alcohol.
Date: August 1, 1993
Creator: Tung, L. A.
System: The UNT Digital Library
Theoretical studies of zirconium and carbon clusters with molecular dynamics simulations (open access)

Theoretical studies of zirconium and carbon clusters with molecular dynamics simulations

In this dissertation, we will present a systematic study of structures of fullerenes ranging from C{sub 20} to C{sub 100} by introducing a novel scheme. Using our new scheme, we not only reproduce all known fullerene structures but also successfully predicted several other fullerene structures which were confirmed by experiments. By utilizing the tight-binding molecular-dynamic (TBMD) simulation, we also studied the dynamical behavior of fullerenes: Vibrations, thermal disintegration of individual clusters as well as collisions between fullerenes. If the beauty of carbon fullerene is not enough, people found that carbon can also form tubules and even speculated that they can form three-dimensional graphite-like networks. By extending our fullerene structure searching scheme, we performed a search for the ground-state structure of three dimensional carbon network. We found the most stable structure people ever proposed for simple cubic based networks. From the difference of this new form of carbon and graphite in the electronic and vibrational properties, we propose an experimental probe to identify these novel three-dimensional carbon networks.
Date: August 1, 1993
Creator: Zhang, B.
System: The UNT Digital Library
Quenching of the excited state of hydrated Europium(III) ions by electron transfer (open access)

Quenching of the excited state of hydrated Europium(III) ions by electron transfer

This thesis explores the oxidation-reduction chemistry of the excited state of Eu(III) ions, *Eu{sub aq}{sup 3+}, in aqueous solutions. Evidence is presented for the quenching of *Eu{sup 3+} by reductive electron transfer. It is concluded that *Eu{sup 3+} is not a strong energy transfer reagent. The reactivity of *Eu{sub aq}{sup 3+} is compared with that of *UO{sub 2}{sup 2+}.
Date: August 1, 1993
Creator: Christensen, K.
System: The UNT Digital Library
High-resolution soft x-ray photoionization studies of selected molecules (open access)

High-resolution soft x-ray photoionization studies of selected molecules

Near-edge soft x-ray photoionization spectra were measured for CO, SF{sub 6}, H{sub 2}S, and D{sub 2}S in the gas phase, using the Free University of Berlin plane-grating SX-700-II monochromator at the synchrotron radiation source BESSY. Photoionization spectra of carbon monoxide were measured near the carbon and oxygen K edges. Vibrational spacings and bond lengths are derived for several resonances. Results are consistent with equivalent-core model and indicate the different influences of the carbon and oxygen Is core holes. Corresponding spectra of H{sub 2}CO and D{sub 2}CO were also measured. Assignment of complex vibrational structure in valence-shell and Rydberg resonances is facilitated by comparison of spectra for the two isotopic species. Geometric and vibrational parameters are derived for several carbon 1s core-excited states. Isotopic shifts are observed in the energies and linewidths of some core-excited states. Sulfur hexafluoride photoionization spectra, measured near the sulfur L{sub 2,3} edges, show several series of weak, narrow Rydberg resonances. High resolution and good counting statistics allow a complete assignment of these states. Lineshapes of the broad inner-well resonances are analyzed to establish the magnitudes of vibrational and lifetime broadening in these states. Spectra of the H{sub 2}S and D{sub 2}S molecules were also measured near …
Date: August 1, 1993
Creator: Hudson, E. A.
System: The UNT Digital Library
Sulfur-bonded thiophenes in organometallic rhenium complexes and adsorption of isocyanides on gold (open access)

Sulfur-bonded thiophenes in organometallic rhenium complexes and adsorption of isocyanides on gold

This dissertation contains results of research conducted in two different areas: (1) organometallic synthesis and reactivity, and (2) organometallic surface chemistry. In the synthesis and reactivity studies, sulfur coordination of thiophene and benzo[b]thiophene to the metal center in organometallic rhenium complexes is examined. In the surface chemistry studies, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is used to analyze the adsorption of several isocyanides on the surface of gold powder. Results are compared and contrasted to known organometallic chemistry.
Date: August 1, 1993
Creator: Robertson, M. J.
System: The UNT Digital Library
Role of surface characteristics in urban meteorology and air quality (open access)

Role of surface characteristics in urban meteorology and air quality

Urbanization results in a landscape with significantly modified surface characteristics. The lower values of reflectivity to solar radiation, surface moisture availability, and vegetative cover, along with the higher values of anthropogenic heat release and surface roughness combine to result higher air temperatures in urban areas relative to their rural counterparts. Through their role in the surface energy balance and surface exchange processes, these surface characteristics are capable of modifying the local meteorology. The impacts on wind speeds, air temperatures, and mixing heights are of particular importance, as they have significant implications in terms of urban energy use and air quality. This research presents several major improvements to the meteorological modeling methodology for highly heterogeneous terrain. A land-use data-base is implemented to provide accurate specification of surface characteristic variability in simulations of the Los Angeles Basin. Several vegetation parameterizations are developed and implemented, and a method for including anthropogenic heat release into the model physics is presented. These modeling advancements are then used in a series of three-dimensional simulations which were developed to investigate the potential meteorological impact of several mitigation strategies. Results indicate that application of moderate tree-planting and urban-lightening programs in Los Angeles may produce summertime air temperature reductions …
Date: August 1, 1993
Creator: Sailor, D. J.
System: The UNT Digital Library
Iterative electromagnetic Born inversion applied to earth conductivity imaging (open access)

Iterative electromagnetic Born inversion applied to earth conductivity imaging

This thesis investigates the use of a fast imaging technique to deduce the spatial conductivity distribution in the earth from low frequency (< 1 MHz), cross well electromagnetic (EM) measurements. The theory embodied in this work is the extension of previous strategies and is based on the Born series approximation to solve both the forward and inverse problem. Nonlinear integral equations are employed to derive the series expansion which accounts for the scattered magnetic fields that are generated by inhomogeneities embedded in either a homogenous or a layered earth. A sinusoidally oscillating, vertically oriented magnetic dipole is employed as a source, and it is assumed that the scattering bodies are azimuthally symmetric about the source dipole axis. The use of this model geometry reduces the 3-D vector problem to a more manageable 2-D scalar form. The validity of the cross well EM method is tested by applying the imaging scheme to two sets of field data. Images of the data collected at the Devine, Texas test site show excellent correlation with the well logs. Unfortunately there is a drift error present in the data that limits the accuracy of the results. A more complete set of data collected at the …
Date: August 1, 1993
Creator: Alumbaugh, D. L.
System: The UNT Digital Library