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Hard photo-disintegration of proton pairs in {sup 3}He nuclei

Description: Extensive studies of high-energy deuteron photodisintegration over the past two decades have probed the limits of meson-baryon descriptions of nuclei and nuclear reactions. At high energies, photodisintegration cross sections have been shown to scale as a power law in s (the total cm energy squared), which suggests that quarks are the relevant degrees of freedom. In an attempt to more clearly identify the underlying dynamics at play, JLab/Hall A experiment 03-101 measured the hard photodisintegration of {sup 3}He into p-p and p-d pairs at θ{sub c.m.} = 90◦ and E{sub {gamma}} = 0.8 - 4.7 GeV. The basic idea is that the measurement should be able to test theoretical predictions for the relative size of pp versus pn disintegrations. This document presents data for the energy dependence of the high energy 90◦ c.m. photodisintegration of {sup3]He: dσ/dt(γ + {sup3}He → p + p + n{sub spectator}), and dσ/dt(γ + {sup 3}He → p + d). The cross sections were observed to scale as a function of s{sup −n} where n was found to be 11.1±0.1 and 17.4±0.5 for the two reactions respectively. The degree of scaling found for d#27;{sigma}/dt (γ + {sup 3}He → p + d) is the highest degree of scaling ever observed in a nuclear process. The onset of the observed scaling are at photon energy of 2.2 GeV for the pp breakup and 0.7 GeV for the pd breakup. The magnitude of the invariant cross section for pp pair breakup was found to be dramatically lower than for the breakup of pn pairs and theoretical predictions. At energies below the scaling region, the scaled cross section was found to present a strong energy-dependent structure not observed in the pn breakup. The data indicate a transition from three-nucleon hadronic photodisintegration processes at low energies to two-nucleon quark-dominated ...
Date: September 1, 2011
Creator: Pomerantz, Ishay
Partner: UNT Libraries Government Documents Department

Analysis and Development of FACE Automatic Apparatus for Rapid Identification of Transuranium Isotopes

Description: A description of and operating manual for the FACE Automatic Apparatus has been written along with a documentation of the FACE machine operating program, to provide a user manual for the FACE Automatic Apparatus. In addition, FACE machine performance was investigated to improve transuranium throughput. Analysis of the causes of transuranium isotope loss was undertaken both chemical and radioactive. To lower radioactive loss, the dynamics of the most time consuming step of the FACE machine, the chromatographic column output droplet drying and flaming, in preparation of sample for alpha spectroscopy and counting, was investigated. A series of droplets were dried in an experimental apparatus demonstrating that droplets could be dried significantly faster through more intensie heating, enabling the FACE machine cycle to be shortened by 30-60 seconds. Proposals incorporating these ideas were provided for FACE machine development. The 66% chemical loss of product was analyzed and changes were proposed to reduce the radioisotopes product loss. An analysis of the chromatographic column was also provided. All operating steps in the FACE machine are described and analyzed to provide a complete guide, along with the proposals for machine improvement.
Date: September 1, 1978
Creator: Sebesta, E.H.
Partner: UNT Libraries Government Documents Department

Coupling of the 4f Electrons in Lanthanide Molecules

Description: (C5Me5)2LnOTf where Ln = La, Ce, Sm, Gd, and Yb have been synthesized and these derivatives are good starting materials for the synthesis of (C5Me5)2LnX derivatives. (C5Me5)2Ln(2,2'-bipyridine), where Ln = La, Ce, Sm, and Gd, along with several methylated bipyridine analogues have been synthesized and their magnetic moments have been measured as a function of temperature. In lanthanum, cerium, and gadolinium complexes the bipyridine ligand ligand is unequivocally the radical anion, and the observed magnetic moment is the result of intramolecular coupling of the unpaired electron on the lanthanide fragment with the unpaired electron on the bipyridine along with the intermolecular coupling between radicals. Comparison with the magnetic moments of the known compounds (C5Me5)2Sm(2,2'-bipyridine) and (C5Me5)2Yb(2,2'-bipyridine) leads to an understanding of the role of the Sm(II)/Sm(III) and Yb(II)/Yb(III) couple in the magnetic properties of (C5Me5)2Sm(2,2'-bipyridine) and (C5Me5)2Yb(2,2'-bipyridine). In addition, crystal structures of (C5Me5)2Ln(2,2'-bipyridine) and [(C5Me5)2Ln(2,2'-bipyridine)][BPh4](Ln= Ce and Gd), where the lanthanide is unequivocally in the +3 oxidation state, give the crystallographic characteristics of bipyridine as an anion and as a neutral ligand in the same coordination environment, respectively. Substituted bipyridine ligands coordinated to (C5Me5)2Yb are studied to further understand how the magnetic coupling in (C5Me5)2Yb(2,2'-bipyridine) changes with substitutions. In the cases of (C5Me5)2Yb(5,5'-dimethyl-2,2'-bipyridine) and (C5Me5)2Yb(6-methyl-2,2'-bipyridine), the valence, as measured by XANES, changes as a function of temperature. In general, the magnetism in complexes of the type (C5Me5)2Yb(bipy.-), where bipyo represents 2,2'-bipyridine and substituted 2,2'-bipyridine ligands, is described by a multiconfiguration model, in which the ground state is an open-shell singlet composed of two configurations: Yb(III, f13)(bipy.-) and Yb(II, f14)(bipyo). The relative contributions of the two configurations depends on the substituents on the bipyridine ligand.[(C5H4Me)3Ln]2(L) (Ln = Ce, Tb; L = 4,4'-bipyridine, 1,4-benzoquinone) are synthesized in order to study the effect of these ligands on the oxidation states of the metal ...
Date: September 12, 2008
Creator: Kazhdan, Daniel
Partner: UNT Libraries Government Documents Department

Quantum electrodynamics with the spear magnetic detector

Description: One makes a study of quantum electrodynamic processes which are present at the SPEAR colliding beam magnetic detector. We begin by describing the experiment performed by the SLAC-LBL collaboration and the results concerning the strong interaction. Then the interactions e$sup +$e$sup -$ $Yields$ e$sup +$e$sup -$ and e$sup +$e$sup -$ $Yields$ $mu$$sup +$$mu$$sup -$ are considered along with their third-order radiative corrections. These events, previously used to determine new limits for cutoff parameters in QED breakdown models, are further studied to show that the full distribution in coplanarity angle fits the theoretical prediction well. The major focus is on the fourth order two-photon process, e$sup +$e$sup -$ $Yields$ e$sup +$e$sup -$A$sup +$A$sup -$, which only recently has been realized to be significant in such experiments. Cross sections are derived and calculated exactly for this process and the results compared to a Weizacker-Williams equivalent photon calculation. The two-photon data are then isolated and fit to the calculation. A special experiment was done where the small-angle scattered electron or positron is ''tagged'' along with particles in the main detector. Cross sections and coplanarity distributions are measured and compared to calculation. Through these studies, one feels confident that one understand the nature of the two-photon process in the detector. One further explores the hadronic physics of the two-photon process, e$sup +$e$sup -$ $Yields$ e$sup +$e$sup -$ hadrons, measuring pion cross sections, searching for resonances, and discussing future experiments. (auth)
Date: September 1, 1975
Creator: Zipse, J.E.
Partner: UNT Libraries Government Documents Department

Vibrational inelasticity in H$sub 2$ collisions with He and Li$sup +$

Description: The partially averaged version of classical S-matrix theory was applied to three-dimensional collisions of H$sub 2$ with He and Li$sup +$. For H$sub 2$- Li$sup +$, cross-sections for the de-excitation of H$sub 2$ from (n$sub 1$,j$sub 1$) = (1,0) to the ground vibrational manifold were computed at a total energy of 1.2 eV and compared to previously done coupled channel calculations of Schaefer and Lester. The agreement is very good. For H$sub 2$-He, the Kutzelnigg- Tsapline interaction potential was extended to small atom-diatom separations, the ab initio points were then fit to an analytic form, and cross sections for the de- excitation of H$sub 2$ from the states (n$sub 1$,j$sub 1$), n$sub 1$ = 1, j$sub 1$ = 0,2,4 to the ground vibrational manifold were computed at total energies of .9, 1.1, 1.3 and 1.5 eV. For comparison, coupled channel calculations were also performed on the system at the same energies. The agreement was poorer than in the H$sub 2$-Li$sup +$ case, for identifiable reasons. The cross sections were used to compute rate constants and relaxation times for the H$sub 2$-He system. Comparison of these results with the results of experiment and of other calculations shows good agreement, certainly within the expected errors. (7 figs., 30 refs., 3 tables) (auth)
Date: September 1, 1975
Creator: Raczkowski, A.W.
Partner: UNT Libraries Government Documents Department

Far infrared spectroscopy of solids. I. Impurity states in Al$sub 2$O$sub 3$. II. Electron-hole droplets in Ge

Description: Far infrared Fourier transform spectroscopy was used to study the low lying vibronic states of Mn$sup 3+$ in Al$sub 2$O$sub 3$ and the plasma absorption of electron-hole droplets in Ge. The transmission of Mn-doped samples of Al$sub 2$O$sub 3$ was measured in the frequency range from 3 to 30 cm$sup -1$ in applied magnetic fields up to 50 kG. Absorption lines were observed due to both ground and excited state transitions. Polarization measurements established that these absorption lines were due to electric dipole transitions. Temperature dependence measurements were used to derive a level diagram for the low lying states of Mn$sup 3+$. A phenomenological model based on an electronic Hamiltonian was developed which successfully describes the data. The empirically determined trigonal field and spin-orbit quenching parameters of this model are 0.7 and 0.1 respectively. This quenching is attributed to the dynamic Jahn-- Teller interaction. The plasma absorption of small ($alpha$) electron-hole drops in Ge was measured in the frequency range from 30 to 300 cm$sup -1$. The observed absorption is in good agreement with measurements by Vavilov and other workers. A theoretical model which includes both intraband and interband contributions to the dielectric constant in the Rayleigh limit of Mie theory is used to describe the observed lineshape. Measurements of plasma absorption of large ($gamma$) drops in inhomogeneously stressed Ge were made in magnetic fields up to 50 kG. The lineshape at zero applied field was calculated in the large sphere limit of Mie theory including intraband terms and a zero-strain interband term. Qualitative agreement with experiment was obtained. The peak absorption shifted quadratically with applied magnetic field and the total plasma absorption increased. No oscillatory structure was observed in the field-dependence of the total absorption. (auth)
Date: September 12, 1975
Creator: Aurbauch, R.L.
Partner: UNT Libraries Government Documents Department

Determination of the K/sub L/$sup 0$ $Yields$ $pi$$sup -$$mu$$sup +$$nu$/ sub $mu$/ form factor xi(q$sup 2$) by muon polarization measurements

Description: The polarization of the muon in the decay K$sup 0$/sub L/ $Yields$ $pi$$sup -$$mu$$sup +$$nu$/sub $mu$/ was measured as a function of q$sup 2$, the four-momentum transferred to the lepton pair. The kinematic information was used to compute the polarization expected on the basis of various assumed values of the form factor xi(q$sup 2$). By comparing the interpolated curve of the polarization as a function of xi(q$sup 2$) to the experimentally measured polarization, one has determined xi(q$sup 2$) as a function of q$sup 2$. If one parameterizes the q$sup 2$ dependence of xi by xi(q$sup 2$) = xi(0) + $lambda$ q$sup 2$/m$sup 2$/sub $pi$/, then xi(0) = 0.178 +- 0.105 - 3.80 $lambda$. (auth)
Date: September 1, 1975
Creator: Shen, G.
Partner: UNT Libraries Government Documents Department

Application of generalized classical trajectories in nuclear physics

Description: A new semi-classical method, the so-called uniform semiclassical approximation, is described briefly and then applied to two nuclear physics problems. The basic features of this method are that the dynamics of the problem is treated completely classically (that is, one solves classical equations of motion), but the quantum mechanical superposition principle is retained by evaluating a phase along the classical trajectory and adding probability amplitudes for indistinguishable processes rather than probabilities themselves. The first problem considered is the backscattering from a deformed nucleus and the excitation of rotational states in the target at energies up to the Coulomb barrier. The multiple Coulomb excitation calculations are in quantitative agreement with a very different method (the de Boer-Winther code). A nuclear optical potential is also considered and the nuclear-Coulomb interference for heavy ions is studied. The second problem considered is the tunneling through a two-dimensional barrier. This problem (which is supposed to simulate the penetration through a two-dimensional fission barrier) is investigated by a fully quantum-mechanical coupled-channel calculation and by the uniform semiclassical approximation. A quantitative agreement is found. (auth)
Date: September 1, 1975
Creator: Leser, H.M.
Partner: UNT Libraries Government Documents Department


Description: A computer model for simulation of the image contrast caused by Frank dislocation loops in field ion tips of fcc materials is presented. The model is based on the shell model for ion image simulation, whereas the displacement field of Frank loops is computed from the exact displacement equation for a closed dislocation loop in an isotropically elastic continuum. A method for taking surface effects into account by superposition of the displacement field of an image loop is introduced. The results indicate that Frank loops will cause image contrast while wholly beneath the surface of the tip, and that vacancy and interstitial loops will cause qualitatively different contrast. The effect of surface relaxation, while quantitatively substantial, does not qualitatively alter these results. Special emphasis is placed on small loops, with respect to which existing contrast theory is inadequate. Some micrographs of ion bombarded iridium tips are presented. These micrographs display contrast effects in excellent agreement with computer plots of interstitial loop contrast.
Date: September 1, 1973
Creator: Stolt, Kaj Gunnar
Partner: UNT Libraries Government Documents Department

A Measurement of the Top Quark Mass in 1.96 TeV Proton-Antiproton Collisions Using a Novel Matrix Element Method

Description: A measurement of the top quark mass in t{bar t} {yields} l + jets candidate events, obtained from p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector, is presented. The measurement approach is that of a matrix element method. For each candidate event, a two dimensional likelihood is calculated in the top pole mass and a constant scale factor, 'JES', where JES multiplies the input particle jet momenta and is designed to account for the systematic uncertainty of the jet momentum reconstruction. As with all matrix element techniques, the method involves an integration using the Standard Model matrix element for t{bar t} production and decay. However, the technique presented is unique in that the matrix element is modified to compensate for kinematic assumptions which are made to reduce computation time. Background events are dealt with through use of an event observable which distinguishes signal from background, as well as through a cut on the value of an event's maximum likelihood. Results are based on a 955 pb{sup -1} data sample, using events with a high-p{sub T} lepton and exactly four high-energy jets, at least one of which is tagged as coming from a b quark; 149 events pass all the selection requirements. They find M{sub meas} = 169.8 {+-} 2.3(stat.) {+-} 1.4(syst.) GeV/c{sup 2}.
Date: September 30, 2007
Creator: CDF Collaboration
Partner: UNT Libraries Government Documents Department

A Search for Neutral Supersymmetric Higgs Bosons at D0

Description: A search for Higgs bosons in multijet data from the D0 detector is reported in this thesis. The Higgs boson is the only remaining undiscovered particle in the Standard Model of particle physics, and plays an integral role in this model. It is known that this model is not a complete description of fundamental physics (it does not describe gravity, for example), and so searches for physics beyond the Standard Model are an important part of particle physics. One extension of the Standard Model, the Minimal Supersymmetric Standard Model (MSSM), predicts the existence of five Higgs bosons, two of which can show an enhanced coupling to bottom quarks. For this reason, a search in the bbb (multijet) channel is a sensitive test of Higgs boson physics. The analysis described in this thesis was conducted over 6.6 fb{sup -1} of data. At the time of writing, the best limits on tan {beta} (a key parameter of the MSSM) in the multijet channel were set by D0. The new analysis described in this thesis included more data than the previous analysis in the channel, and made use of a new trigger and event-based analysis method. An improved Multivariate Analysis technique was used to separate signal and background events and produce a final discriminant for the limit setting process. These changes increased the expected sensitivity of this measurement by roughly 50% more than would be expected from the increase in the size of data sample alone.
Date: September 1, 2010
Creator: Osman, Nicolas Ahmed & /Imperial Coll., London
Partner: UNT Libraries Government Documents Department

Numerical investigation of the pulsed NF3 + H2 chemical laser using a model which includes rotational relaxation and semi-classical laser equations

Description: Waveforms and population distributions have been calculated by a numerical model and compared with experiment for an electric-discharge-initiated, pulsed NF$sub 3$ + H$sub 2$ chemical laser. The model treats each vibrational- rotational state separately, allowing rotational relaxation between adjacent states as well as vibrational relaxation and lasing according to P-branch selection rules. Calculated waveforms agree with experiment and show several features not seen when rotational equilibrium is assumed: simultaneous lasing on many transitions, cascade behavior, spikes due to laser relaxation oscillations, non-Boltzmann rotational distributions, and ''hole burning'' in the population distributions. The calculations give insight into the physical phenomena governing the shape and duration of the waveforms. The effect of varying certain parameters, relaxation rates, temperature, pressure, and diluents, is studied. Best fit to experimental waveforms is obtained when the rotational relaxation rate and collisional line broadening rate are approximately equal at about 10 times the hard sphere collision rate. The IXION computer code, developed for these calculations, is described in detail. In addition, an analytic model is presented which accounts for major features of the total (all transitions) output waveform of the laser assuming rotational equilibrium, a steady state laser model, and constant temperature. A second computer code, MINOTAR, was developed as a general purpose chemical kinetics code. It verifies the analytic model and extends the results to adiabatic reactions where the temperature varies, and can yield waveforms using the assumptions of rotational equilibrium and a steady state laser. The MINOTAR code, being general, can also be used for chemical kinetics problems such as air pollution and combustion. (auth)
Date: September 1, 1975
Creator: Creighton, J.R.
Partner: UNT Libraries Government Documents Department

Search for Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT

Description: Large extra dimensions (LED) have been proposed to account for the apparent weakness of gravitation. These theories also indicate that the postulated massive Kaluza-Klein (KK) gravitons may be produced by nucleon-nucleon bremsstrahlung in the course of core collapse of supernovae. Hannestad and Raffelt have predicted energy spectra of gamma ray emission from the decay of KK gravitons trapped by the gravity of the remnant neutron stars (NS). These and other authors have used EGRET data on NS to obtain stringent limits on LED. Fermi-LAT is observing radio pulsar positions obtained from radio and x-ray catalogs. NS with certain characteristics are unlikely emitter of gamma rays, and emit in radio and perhaps x-rays. This talk will focus on the blind analysis we plan to perform, which has been developed using the 1st 2 months of all sky data and Monte Carlo simulations, to obtain limits on LED based on about 1 year of Fermi-LAT data. Preliminary limits from this analysis using these first 2 months of data will be also be discussed.
Date: September 19, 2012
Creator: Berenji, Bijan & /Stanford U., Appl. Phys. Dept. /SLAC
Partner: UNT Libraries Government Documents Department

Polarized {sup 3}He(e,e'n) Asymmetries in Three Orthogonal Measurements

Description: Asymmetry measurements were conducted in Jefferson Lab's experimental Hall A through electron scattering from a polarized {sup 3}He target in the quasi-elastic polarized-{sup 3}He(e,e'n) reaction. Measurements were made with the target polarized in the longitudinal direction with respect to the incoming electrons A_L, in a transverse direction that was orthogonal to the beam-line and parallel to the q-vector A_T, and in a vertical direction that was orthogonal to both the beam-line and the q-vector (A_y^0). The experiment measured $A_y^0$ at four-momentum transfer squared Q^2 of 0.127 (GeV/c)^2, 0.456 (GeV/c)^2, and 0.953 (GeV/c)^2. The A_T and A_L asymmetries were both measured at Q^2 of 0.505 (GeV/c)^2 and 0.953 (GeV/c)^2. This is the first time that three orthogonal asymmetries have been measured simultaneously. Results from this experiment are compared with the plane wave impulse approximation (PWIA) and Faddeev calculations. These results provide important tests of models that use 3He as an effective neutron target and show that the PWIA holds above Q^2 of 0.953 (GeV/c)^2.
Date: September 1, 2012
Creator: Long, Elena
Partner: UNT Libraries Government Documents Department

Observation of Bs-Bsbar Oscillations Using Partially Reconstructed Hadronic Bs Decays

Description: This thesis describes the contribution of partially reconstructed hadronic decays in the world's first observation of B{sub s}{sup 0}-{bar B}{sub s}{sup 0} oscillations. The analysis is a core member of a suite of closely related studies whose combined time-dependent measurement of the B{sub s}{sup 0}-{bar B}{sub s}{sup 0} oscillation frequency {Delta}m{sub s} is of historic significance. Using a data sample of 1 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV collected with the CDF-II detector at the Fermilab Tevatron, they find signals of 3150 partially reconstructed hadronic B{sub s} decays from the combined decay channels B{sub s}{sup 0} {yields} D*{sub s}{sup -} {pi}{sup +} and B{sub s}{sup 0} {yields} D{sub s}{sup -} {rho}{sup +} with D{sub s}{sup -} {yields} {phi}{pi}{sup -}. These events are analyzed in parallel with 2000 fully reconstructed B{sub s}{sup 0} {yields} D{sub s}{sup -} {pi}{sup +} (D{sub s}{sup -} {yields} {phi}{pi}{sup -}) decays. The treatment of the data is developed in stages of progressive complexity, using high-statistics samples of hadronic B{sup 0} and B{sup +} decays to study the attributes of partially reconstructed events. The analysis characterizes the data in mass and proper decay time, noting the potential of the partially reconstructed decays for precise measurement of B branching fractions and lifetimes, but consistently focusing on the effectiveness of the model for the oscillation measurement. They efficiently incorporate the measured quantities of each decay into a maximum likelihood fitting framework, from which they extract amplitude scans and a direct measurement of the oscillation frequency. The features of the amplitude scans are consistent with expected behavior, supporting the correctness of the calibrations for proper time uncertainty and flavor tagging dilution. The likelihood allows for the smooth combination of this analysis with results from other data samples, including 3500 fully reconstructed hadronic B{sub s} events ...
Date: September 1, 2007
Creator: Miles, Jeffrey Robert & /MIT
Partner: UNT Libraries Government Documents Department

Analysis of Bs flavor oscillations at CDF

Description: The search for and study of flavor oscillations in the neutral B{sub s}B{sub s} meson system is an experimentally challenging task. It constitutes a flagship analysis of the Tevatron physics program. In this dissertation, they develop an analysis of the time-dependent B{sub s} flavor oscillations using data collected with the CDF detector. The data samples are formed of both fully and partially reconstructed B meson decays: B{sub s} {yields} D{sub s}{pi}({pi}{pi}) and B{sub s} {yields} D{sub s}lv. A likelihood fitting framework is implemented and appropriate models and techniques developed for describing the mass, proper decay time, and flavor tagging characteristics of the data samples. The analysis is extended to samples of B{sup +} and B{sup 0} mesons, which are further used for algorithm calibration and method validation. The B mesons lifetimes are extracted. The measurement of the B{sup 0} oscillation frequency yields {Delta}m{sub d} = 0.522 {+-} 0.017 ps{sup -1}. The search for B{sub s} oscillations is performed using an amplitude method based on a frequency scanning procedure. Applying a combination of lepton and jet charge flavor tagging algorithms, with a total tagging power {epsilon}'D{sup 2} of 1.6%, to a data sample of 355 pb{sup -1}, a sensitivity of 13.0 ps{sup -1} is achieved. They develop a preliminary same side kaon tagging algorithm, which is found to provide a superior tagging power of about 4.0% for the B{sub s} meson species. A study of the dilution systematic uncertainties is not reported. From its application as is to the B{sub s} samples the sensitivity is significantly increased to about 18 ps{sup -1} and a hint of a signal is seen at about 175. ps{sup -1}. They demonstrate that the extension of the analysis to the increasing data samples with the inclusion of the same side tagging algorithm is capable of providing ...
Date: September 1, 2006
Creator: Leonardo, Nuno T. & /MIT
Partner: UNT Libraries Government Documents Department

Observations and Measurements of Orbitally Excited L=1 B Mesons at the D0 Experiment

Description: This thesis describes investigations of the first set of orbitally excited (L = 1) states for both the B{sub d}{sup 0} and B{sub s}{sup 0} meson systems (B**{sub d} and B**{sub s}). The data sample corresponds to 1.35 fb{sup -1} of integrated luminosity, collected in 2002-2006 by the D0 detector, during the Run IIa operation of the Tevatron p{bar p} colliding beam accelerator. The B**{sub d} states are fully reconstructed in decays to B{sup (*)+} {pi}{sup -}, with B{sup (*)+} {yields} {gamma} J/{psi}K{sup +}, J/{psi} {yields} {mu}{sup +}{mu}{sup -}, yielding 662 {+-} 91 events, and providing the first strong evidence for the resolution of two narrow resonances, B{sub 1} and B*{sub 2}. The masses are extracted from a binned {chi}{sup 2} fit to the invariant mass distribution, giving M(B{sub 1}) = 5720.7 {+-} 2.4(stat.) {+-} 1.3(syst.) {+-} 0.5 (PDG) MeV/c{sup 2} and M(B*{sub 2}) = 5746.9 {+-} 2.4(stat.) {+-} 1.0(syst.) {+-} 0.5(PDG) MeV/c{sup 2}. The production rate of narrow B**{sub d} {yields} B{pi} resonances relative to the B{sup +} meson is determined to be [13.9 {+-} 1.9(stat.) {+-} 3.2(syst.)]%. The same B{sup +} sample is also used to reconstruct the analogous states in the B{sub s}{sup 0} system, in decays B**{sub s} {yields} B{sup (*)+} K{sup -}. A single resonance in the invariant mass distribution is found with a statistical significance of 5{sigma}, interpreted as the B*{sub s2} state. The mass is determined to be M(B*{sub s2}) = 5839.6 {+-} 1.1(stat.) {+-} 0.4(syst.) {+-} 0.5(PDG) MeV/c{sup 2}, and the production rate of B*{sub s2} {yields} BK resonances is measured to be a fraction (2.14 {+-} 0.43 {+-} 0.24)% of the corresponding rate for B{sup +} mesons. Alternative fitting hypotheses give inconclusive evidence for the presence of the lighter B{sub s1} meson.
Date: September 1, 2008
Creator: Williams, Mark Richard James & U., /Lancaster
Partner: UNT Libraries Government Documents Department

A Parallel Ocean Model With Adaptive Mesh Refinement Capability For Global Ocean Prediction

Description: An ocean model with adaptive mesh refinement (AMR) capability is presented for simulating ocean circulation on decade time scales. The model closely resembles the LLNL ocean general circulation model with some components incorporated from other well known ocean models when appropriate. Spatial components are discretized using finite differences on a staggered grid where tracer and pressure variables are defined at cell centers and velocities at cell vertices (B-grid). Horizontal motion is modeled explicitly with leapfrog and Euler forward-backward time integration, and vertical motion is modeled semi-implicitly. New AMR strategies are presented for horizontal refinement on a B-grid, leapfrog time integration, and time integration of coupled systems with unequal time steps. These AMR capabilities are added to the LLNL software package SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) and validated with standard benchmark tests. The ocean model is built on top of the amended SAMRAI library. The resulting model has the capability to dynamically increase resolution in localized areas of the domain. Limited basin tests are conducted using various refinement criteria and produce convergence trends in the model solution as refinement is increased. Carbon sequestration simulations are performed on decade time scales in domains the size of the North Atlantic and the global ocean. A suggestion is given for refinement criteria in such simulations. AMR predicts maximum pH changes and increases in CO{sub 2} concentration near the injection sites that are virtually unattainable with a uniform high resolution due to extremely long run times. Fine scale details near the injection sites are achieved by AMR with shorter run times than the finest uniform resolution tested despite the need for enhanced parallel performance. The North Atlantic simulations show a reduction in passive tracer errors when AMR is applied instead of a uniform coarse resolution. No dramatic or persistent signs of error growth ...
Date: September 8, 2005
Creator: Herrnstein, A
Partner: UNT Libraries Government Documents Department

Plasma ion sources and ion beam technology inmicrofabrications

Description: For over decades, focused ion beam (FIB) has been playing a very important role in microscale technology and research, among which, semiconductor microfabrication is one of its biggest application area. As the dimensions of IC devices are scaled down, it has shown the need for new ion beam tools and new approaches to the fabrication of small-scale devices. In the meanwhile, nanotechnology has also deeply involved in material science research and bioresearch in recent years. The conventional FIB systems which utilize liquid gallium ion sources to achieve nanometer scale resolution can no longer meet the various requirements raised from such a wide application area such as low contamination, high throughput and so on. The drive towards controlling materials properties at nanometer length scales relies on the availability of efficient tools. In this thesis, three novel ion beam tools have been developed and investigated as the alternatives for the conventional FIB systems in some particular applications. An integrated focused ion beam (FIB) and scanning electron microscope (SEM) system has been developed for direct doping or surface modification. This new instrument employs a mini-RF driven plasma source to generate focused ion beam with various ion species, a FEI two-lens electron (2LE) column for SEM imaging, and a five-axis manipulator system for sample positioning. An all-electrostatic two-lens column has been designed to focus the ion beam extracted from the source. Based on the Munro ion optics simulation, beam spot sizes as small as 100 nm can be achieved at beam energies between 5 to 35 keV if a 5 {micro}m-diameter extraction aperture is used. Smaller beam spot sizes can be obtained with smaller apertures at sacrifice of some beam current. The FEI 2LE column, which utilizes Schottky emission, electrostatic focusing optics, and stacked-disk column construction, can provide high-resolution (as small as 20 nm) ...
Date: September 1, 2007
Creator: Ji, Lili
Partner: UNT Libraries Government Documents Department

First Search for the Standard Model Higgs Boson Using the Semileptonic Decay Channel: H --> WW --> mu bar nu jj

Description: This dissertation presents the first search for the standard model Higgs boson (H) in decay topologies containing a muon, an imbalance in transverse momentum (E{sub T}) and jets, using p{bar p} collisions at {radical}s = 1.96 TeV with an integrated luminosity of 4.3 fb{sup -1} recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primary to contributions from Higgs bosons produced through gluon fusion, with subsequent decay H {yields} WW {yields} {mu}{nu}jj where W represents a real or virtual W boson. In the absence of signal, limits are set at 95% confidence on the production and decay of the standard model Higgs boson for M{sub H} in the range of 115-200 GeV. For M{sub H} = 165 GeV, the observed and expected limits are factors of 11.2 larger than the standard model value. Combining this channel with e{nu}jj final states and including earlier data to increase the integrated luminosity to 5.4 fb{sup -1} produces observed(expected) limits of 5.5(3.8) times the standard model value.
Date: September 1, 2010
Creator: Zelitch, Shannon Maura & U., /Virginia
Partner: UNT Libraries Government Documents Department

Measurement of the inclusive bb jet cross section at the Collidor Detector at Fermilab

Description: Data collected by the Fermilab CDF detector are used to measure the inclusive b{bar b} jet production cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. Vertices displaced from the primary interaction point (secondary vertices) are a signature for long-lived decay and are used to identify jets originating from b quarks. An event sample containing two jets, each having an identified secondary vertex, is used. The jets are required to be within the pseudo-rapidity region |{eta}| < 1.2. One of the jets is required to have a transverse energy greater than 30 GeV and the other jet is required to have a transverse energy greater than 20 GeV. The results are compared to Leading Order (Pythia and Herwig) and Next to Leading Order (MC{at}NLO) predictions.
Date: September 1, 2005
Creator: Gajjar, Anant & U., /Liverpool
Partner: UNT Libraries Government Documents Department