Search for lepton flavor violating decay τ<sup>-</sup> →ℓ<sup>-</sup>ℓ<sup>+</sup>ℓ<sup>-</sup>ℓ = e, μ at BaBar (open access)

Search for lepton flavor violating decay τ<sup>-</sup> →ℓ<sup>-</sup>ℓ<sup>+</sup>ℓ<sup>-</sup>ℓ = e, μ at BaBar

The Standard Model (SM) is one of the most tested and verified physical theories of all time, present experimental observations are consistent with SM expectations. On the other hand SM can not explain many physical observations: the cosmological observations possibly infer the presence of dark matter which is clearly beyond the SM expectations; the SM Higgs model, while explaining the generation of fermion masses, can not explain the hierarchy problem and a non natural fine tuning of SM is needed to cancel out quadratic divergences in the Higgs boson mass. New physics (NP) beyond SM should hence be investigated: rising the energy above NP processes thresholds, and detecting new particles or new effects not predicted by the standard model directly, is one of the possible approaches; another approach is to make precision measurements of well known processes or looking for rare processes which involve higher order contribution from NP processes, this approach need higher luminosities with respect to the previous approach but lower beam energies. Search for Lepton Flavor Violation (LFV) in charged lepton decays is promising: neutrino physics provides indeed a clear and unambiguous evidence of LFV in the neutral lepton sector via mixing processes, which have been observed …
Date: May 26, 2010
Creator: Cervelli, Alberto
System: The UNT Digital Library
Design and Synthesis of Mixed Oxides Nanoparticles for Biofuel Applications (open access)

Design and Synthesis of Mixed Oxides Nanoparticles for Biofuel Applications

The work in this dissertation presents the synthesis of two mixed metal oxides for biofuel applications and NMR characterization of silica materials. In the chapter 2, high catalytic efficiency of calcium silicate is synthesized for transesterfication of soybean oil to biodisels. Chapter 3 describes the synthesis of a new Rh based catalyst on mesoporous manganese oxides. The new catalyst is found to have higher activity and selectivity towards ethanol. Chapter 4 demonstrates the applications of solid-state Si NMR in the silica materials.
Date: May 15, 2010
Creator: Chen, Senniang
System: The UNT Digital Library
Search for the Production of Gluinos and Squarks with the CDF II Experiment at the Tevatron Collider (open access)

Search for the Production of Gluinos and Squarks with the CDF II Experiment at the Tevatron Collider

This thesis reports on two searches for the production of squarks and gluinos, supersymmetric partners of the Standard Model (SM) quarks and gluons, using the CDF detector at the Tevatron √s = 1.96 TeV p$\bar{p}$ collider. An inclusive search for squarks and gluinos pair production is performed in events with large E<sub>T</sub> and multiple jets in the final state, based on 2 fb<sup>-1</sup> of CDF Run II data. The analysis is performed within the framework of minimal supergravity (mSUGRA) and assumes R-parity conservation where sparticles are produced in pairs. The expected signal is characterized by the production of multiple jets of hadrons from the cascade decays of squarks and gluinos and large missing transverse energy E<sub>T</sub> from the lightest supersymmetric particles (LSP). The measurements are in good agreement with SM predictions for backgrounds. The results are translated into 95% confidence level (CL) upper limits on production cross sections and squark and gluino masses in a given mSUGRA scenario. An upper limit on the production cross section is placed in the range between 1 pb and 0.1 pb, depending on the gluino and squark masses considered. The result of the search is negative for gluino and squark masses up to 392 …
Date: May 19, 2010
Creator: De Lorenzo, Gianluca
System: The UNT Digital Library
Search for the Standard Model Higgs Boson associated with a W Boson using Matrix Element Technique in the CDF detector at the Tevatron (open access)

Search for the Standard Model Higgs Boson associated with a W Boson using Matrix Element Technique in the CDF detector at the Tevatron

In this thesis a direct search for the Standard Model Higgs boson production in association with a W boson at the CDF detector in the Tevatron is presented. This search contributes predominantly in the region of low mass Higgs region, when the mass of Higgs boson is less than about 135 GeV. The search is performed in a final state where the Higgs boson decays into two b quarks, and the W boson decays leptonically, to a charged lepton (it can be an electron or a muon) and a neutrino. This work is organized as follows. Chapter 2 gives an overview of the Standard Model theory of particle physics and presents the SM Higgs boson search results at LEP, and the Tevatron colliders, as well as the prospects for the SM Higgs boson searches at the LHC. The dataset used in this analysis corresponds to 4.8 fb<sup>-1</sup> of integrated luminosity of p$\bar{p}$ collisions at a center of mass energy of 1.96 TeV. That is the luminosity acquired between the beginning of the CDF Run II experiment, February 2002, and May 2009. The relevant aspects, for this analysis, of the Tevatron accelerator and the CDF detector are shown in Chapter 3. …
Date: May 1, 2010
Creator: Gonzalez, Barbara Alvarez
System: The UNT Digital Library
Watching Electrons Transfer from Metals to Insulators using Two Photon Photoemission (open access)

Watching Electrons Transfer from Metals to Insulators using Two Photon Photoemission

Ultrafast angle-resolved two photon photoemission was used to study the dynamics and interfacial band structure of ultrathin films adsorbed onto Ag(111). Studies focused on the image potential state (IPS) in each system as a probe for measuring changes in electronic behavior in differing environments. The energetics and dynamics of the IPS at the toluene/Ag(111) interface are strongly dependent upon coverage. For a single monolayer, the first IPS is bound by 0.81 eV below the vacuum level and has a lifetime of 50 femtoseconds (fs). Further adsorption of toluene creates islands of toluene with an exposed wetting layer underneath. The IPS is then split into two peaks, one corresponding to the islands and one corresponding to the monolayer. The wetting layer IPS shows the same dynamics as the monolayer, while the lifetime of the islands increases exponentially with increasing thickness. Furthermore, the island IPS transitions from delocalized to localized within 500 fs, and electrons with larger parallel momenta decay much faster. Attempts were made using a stochastic model to extract the rates of localization and intraband cooling at differing momenta. In sexithiophene (6T) and dihexyl-sexithiophene (DH6T), the IPS was used as a probe to see if the nuclear motion of spectating …
Date: May 1, 2010
Creator: Johns, James E.
System: The UNT Digital Library
Search for Supersymmetry Using Diphoton Events in p anti-p Collisions at a center of mass energy of 1.96-TeV (open access)

Search for Supersymmetry Using Diphoton Events in p anti-p Collisions at a center of mass energy of 1.96-TeV

This dissertation presents the results of a search for supersymmetry in proton-antiproton collisions with a center of mass energy of 1.96 TeV studied with the Collider Detector at Fermilab. Our strategy is to select collisions with two photons in the final state that have the properties of being the decays of very massive supersymmetric particles. This includes looking for large total energy from the decayed particles as well as for the presence of particles that leave the detector without interacting. We find no events using 2.6 fb{sup -1} of data collected during the 2004-2008 collider run of the Fermilab Tevatron which is consistent with the background estimate of 1.4 {+-} 0.4 events. Since there is no evidence of new particles we set cross section limits in a gauge-mediated supersymmetry model with {tilde {chi}}{sub 1}{sup 0} {yields} {gamma}{tilde G}, where the {tilde {chi}}{sub 1}{sup 0} and {tilde G} are the lightest neutralino and the gravitino (the lightest supersymmetric particle), respectively. We set limits on models as a function of the {tilde {chi}}{sub 1}{sup 0} mass and lifetime, producing the world's most sensitive search for {tilde {chi}}{sub 1}{sup 0} by excluding masses up to 149 GeV/c{sup 2} for {tilde {chi}}{sub 1}{sup 0} …
Date: May 1, 2010
Creator: Lee, Eun Sin & A-M, /Texas
System: The UNT Digital Library
Immersed Boundary Methods for High-Resolution Simulation of Atmospheric Boundary-Layer Flow Over Complex Terrain (open access)

Immersed Boundary Methods for High-Resolution Simulation of Atmospheric Boundary-Layer Flow Over Complex Terrain

None
Date: May 12, 2010
Creator: Lundquist, K A
System: The UNT Digital Library
DualTrust: A Trust Management Model for Swarm-Based Autonomic Computing Systems (open access)

DualTrust: A Trust Management Model for Swarm-Based Autonomic Computing Systems

Trust management techniques must be adapted to the unique needs of the application architectures and problem domains to which they are applied. For autonomic computing systems that utilize mobile agents and ant colony algorithms for their sensor layer, certain characteristics of the mobile agent ant swarm -- their lightweight, ephemeral nature and indirect communication -- make this adaptation especially challenging. This thesis looks at the trust issues and opportunities in swarm-based autonomic computing systems and finds that by monitoring the trustworthiness of the autonomic managers rather than the swarming sensors, the trust management problem becomes much more scalable and still serves to protect the swarm. After analyzing the applicability of trust management research as it has been applied to architectures with similar characteristics, this thesis specifies the required characteristics for trust management mechanisms used to monitor the trustworthiness of entities in a swarm-based autonomic computing system and describes a trust model that meets these requirements.
Date: May 1, 2010
Creator: Maiden, Wendy M.
System: The UNT Digital Library
Measurement of branching fraction ratios and CP asymmetries in B &#8594D0 CPK decays with the BABAR detector (open access)

Measurement of branching fraction ratios and CP asymmetries in B &#8594D0 CPK decays with the BABAR detector

The primary goals of the BABAR experiment are the detection of CP violation (CPV) in the B meson system, the precise measurement of some of the elements of the CKM matrix and the measurement of the rates of rare B meson decays. At present, BABAR has achieved major successes: (1) the discovery, in neutral B decays, of direct and mixing-induced CP violation; (2) accurate measurements of the magnitudes of the CKM matrix elements |V{sub cb}| and |V{sub ub}|; (3) a precise measurement of the CKM parameter {beta} {triple_bond} arg[- V{sub cd}V*{sub cb}/V{sub td}V*{sub tb}]; (4) a first measurement of the CKM parameters {alpha} {triple_bond} arg[- V{sub td}V*{sub tb}/V{sub ud}V*{sub ub}], {gamma} {triple_bond} arg[- V{sub ud}V*{sub ub}/V{sub cd}V*{sub cb}]; and (5) the observation of several rare B decays and the discovery of new particles (in the charmed and charmonium mesons spectroscopy). However, the physics program of BABAR is not yet complete. Two of the key elements of this program that still need to be achieved are: (1) the observation of direct CP violation in charged B decays, which would constitute the first evidence of direct CPV in a charged meson decay; and (2) the precise measurement of {alpha} and {gamma}, which …
Date: May 5, 2010
Creator: Marchiori, Giovanni & U., /Pisa
System: The UNT Digital Library
Measurement of the \textit{CP} Violating Phase $\boldsymbol{\sin(2\beta_{s})}$ using $\boldsymbol{B^{0}_{s}\rightarrow J/\psi\phi}$ Decays at CDF (open access)

Measurement of the \textit{CP} Violating Phase $\boldsymbol{\sin(2\beta_{s})}$ using $\boldsymbol{B^{0}_{s}\rightarrow J/\psi\phi}$ Decays at CDF

A B{sub s}{sup 0} meson can oscillate into its anti-particle, the {bar B}{sub s}{sup 0} meson, before decaying. CP violation in this system is made possible by the presence of amplitudes from both mixed and unmixed B{sub s}{sup 0} meson decays. The CP violating phase {beta}s appears in the interference between the decay amplitudes. The quantity sin(2{beta}s) is expected to be small in the standard model. Thus, measuring a large value for sin(2{beta}s) would be an unequivocal sign of new physics participation in the B{sub s}{sup 0} mixing loop diagram. In this thesis, we present a latest measurement of sin(2{beta}s), using 5.2 fb{sup -1} of data collected at CDF from p{bar p} collisions at a center of mass energy of {radical}s = 1.96 TeV. A time-dependent angular analysis, with the production flavor of the B{sub s}{sup 0} meson identified with flavor tagging methods, is used to extract sin(2{beta}s) from {approx}6500 B{sub s}{sup 0} {yields} J/{psi}{phi} decays. Other parameters of interest, such as the B{sub s}{sup 0} lifetime and the decay width difference {Delta}{Lambda} between the heavy and light B{sub s}{sup 0} mass eigenstates are determined to high precision. Also, the effect of potential contributions to the final state from B{sub …
Date: May 1, 2010
Creator: Pueschel, Elisa
System: The UNT Digital Library
A search for the Standard Model Higgs boson in the process ZH → ℓ<sup>+</sup>ℓ<sup>-</sup>b$\bar{b}$ in  4.1 fb<sup>-1</sup> of CDF II data (open access)

A search for the Standard Model Higgs boson in the process ZH → ℓ<sup>+</sup>ℓ<sup>-</sup>b$\bar{b}$ in 4.1 fb<sup>-1</sup> of CDF II data

The standard model of particle physics provides a detailed description of a universe in which all matter is composed of a small number of fundamental particles, which interact through the exchange of force - carrying gauge bosons (the photon, W <sup>±</sup>, Z and gluons). The organization of the matter and energy in this universe is determined by the effects of three forces; the strong, weak, and electromagnetic. The weak and electromagnetic forces are the low energy manifestations of a single electro-weak force, while the strong force binds quarks into protons and neutrons. The standard model does not include gravity, as the effect of this force on fundamental particles is negligible. Four decades of experimental tests, spanning energies from a few electron-volts (eV) up to nearly two TeV, confirm that the universe described by the standard model is a reasonable approximation of our world. For example, experiments have confirmed the existence of the top quark, the W<sup>±</sup> and the Z bosons, as predicted by the standard model. The latest experimental averages for the masses of the top quark, W<sup>±</sup> and Z are respectively 173.1 ± 0.6(stat.) ± 1.1(syst.), 80.399 ± 0.023 and 91.1876 ± 0.0021 GeV/c<sup>2</sup>. The SM is a gauge …
Date: May 1, 2010
Creator: Shalhout, Shalhout Zaki
System: The UNT Digital Library
Atmospheric Pressure Chemical Ionization Sources Used in The Detection of Explosives by Ion Mobility Spectrometry (open access)

Atmospheric Pressure Chemical Ionization Sources Used in The Detection of Explosives by Ion Mobility Spectrometry

Melanie Waltman's dissertation to be presented on March 24, 2010.
Date: May 1, 2010
Creator: Waltman, Melanie J.
System: The UNT Digital Library
Using Quasi-Elastic Events to Measure Neutrino Oscillations with MINOS Detectors in the NuMI Neutrino Beam (open access)

Using Quasi-Elastic Events to Measure Neutrino Oscillations with MINOS Detectors in the NuMI Neutrino Beam

MINOS (Main Injector Neutrino Oscillation Search) experiment has been designed to search for a change in the flavor composition of a beam of muon neutrinos as they travel between the Near Detector at Fermi National Accelerator Laboratory and the Far Detector in the Soudan mine in Minnesota, 735 km from the target. The MINOS oscillation analysis is mainly performed with the charged current (CC) events and sensitive to constrain high-{Delta}m{sup 2} values. However, the quasi-elastic (QEL) charged current interaction is dominant in the energy region important to access low-{Delta}m{sup 2} values. For further improvement, the QEL oscillation analysis is performed in this dissertation. A data sample based on a total of 2.50 x 10{sup 20} POT is used for this analysis. In summary, 55 QEL-like events are observed at the Far detector while 87.06 {+-} 13.17 (syst.) events are expected with null oscillation hypothesis. These data are consistent with {nu}{sub {mu}} disappearance via oscillation with {Delta}m{sup 2} = 2.10 {+-} 0.37 (stat.) {+-} 0.24 (syst.) eV{sup 2} and the maximal mixing angle.
Date: May 1, 2010
Creator: Watabe, Masaki & University, /Texas A&M
System: The UNT Digital Library