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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

The measurement of the rare kaon decay k-plus to pi-plus, neutrino and anti-neutrino

Ives, Joss 05 1900 (has links)
Brookhaven National Laboratory experiment E949 was designed to search for the rare K meson decay K⁺ → π⁺ , neutrino, and anti-neutrino, a decay sensitive to physics beyond the Standard Model. While previous data analyses dealt with the high π⁺ momentum region accessible for this reaction, this thesis concentrates on the lower range between 140 and 199 MeV/c. Analysis of this low π⁺ momentum region was performed to search for additional evidence of the process K⁺ → π⁺, neutrino, and anti-neutrino. A blind analysis technique was used to avoid bias when developing the selection criteria used to suppress the competing background processes. The blind analysis technique was based on identifying background sources a priori and only examining the signal region once all selection criteria and background estimates had been finalized. The background estimates were performed using a technique known as a "bifurcation method", which relied on using two uncorrelated selection criteria to suppress each background source. The analysis of an exposure of 1.71 x 10¹² K⁺ decays resulted in an observation of three events with an estimated background of 0.927 ± 0.168(stat.)⁺³²⁰-₀.₂₃₇(sys.) events and a single event sensitivity of (4.28 ± 0.43)x 10-¹⁰. Using a likelihood method, the three candidate events observed here were combine with the previous E787 and E949 results, yielding a branching ratio of ϐ(K⁺ → π⁺, neutrino, and anti-neutrino decay of (1.73+1.15-1.05) x 10⁻¹⁰ at the 68% confidence level. This branching ratio is consistent with the prediction of the Standard Model, (0.85 ± 0.07) x 10⁻¹⁰.
132

Particle Size and Bait Preference of the Red Imported Fire Ant, Solenopsis invicta Buren (Hymenoptera: Formicidae)

Neff, Richard R. 2010 August 1900 (has links)
One of the most popular methods for achieving control of the Red Imported Fire Ant, Solenopsis invicta Buren, is through the use of broadcast baits. Several factors contribute to bait efficacy, one of which may be particle size. The goals of these laboratory studies were to determine particle size and bait preference using Advance Select Granular Ant Bait and Advance Carpenter Ant Scatter Bait, determine the effect of starvation on bait removal and recruitment to Carpenter Ant Scatter Bait, and determine if any correlation existed between head capsule width and particle size selected. Experimental colonies removed significantly more 1400-2000 μm particles of Select Granular Ant Bait, while ants foraging on Carpenter Ant Scatter Bait preferred 1000-1400 μm particles. Mean number of ants present at bait mirrored results from bait removal test. Ants displayed a preference for Carpenter Ant Scatter Bait based on mean number of ants present at bait for the 10-d foraging period. For starvation assays, significant differences in bait removal and number of ants present occurred in the 0-d group. Ants starved for 5 d removed significantly more bait of all particle sizes, and removed greater amounts of 1000-1400 μm Carpenter Ant Scatter Bait than other sizes. Head width reliably predicted particle size selected, but the linear model explained very little of the observed variation for ants foraging on Select Granular Ant Bait (R2 = 0.043) or Carpenter Ant Scatter Bait (R2 = 0.047). This study supported the significant role of bait size and starvation period in S. invicta bait preference, and demonstrated how size preference may vary depending on bait type.
133

Particle Impact Damping in the Horizontal Plane

Witt, Bryan 2011 May 1900 (has links)
Particle impact damping is measured for a cantilevered beam vibrating freely in the horizontal plane. Several particle configurations are investigated beginning with a single particle and progressing to multiple layers of particles. The effects of clearance between the particles and enclosure, initial displacement of the primary system, repeatability of damping, and damping efficiency per unit mass added are evaluated for each particle configuration. The investigation shows that the particle configuration significantly affects damping. Configurations with the fewest particles per cavity demonstrate higher damping efficiency per unit mass. Generally, for configurations with a definable clearance between the particles and enclosure, damping is shown to be a function of the clearance and initial system displacement. For configurations with multiple layers of particles, for which horizontal clearance between the particles and enclosure has no meaning, a new dimensionless parameter which captures the geometry of the particle arrangement is proposed.
134

Methodological issues in ultra-low concentration aerosol sampling

McCutcheon, Heather Jean, January 2002 (has links) (PDF)
Thesis--University of Oklahoma. / Includes bibliographical references (leaves 45-46).
135

Geometric properties completely characterizing the set of all the curves of constant pressure in a field of force

Morenus, Eugenie M. January 1922 (has links)
Thesis (Ph. D.)--Columbia University, 1922. / Vita.
136

Noise effects, emittance control, and luminosity issues in laser wakefield accelerators /

Cheshkov, Sergey Valeriev, January 2001 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 97-103). Available also in a digital version from Dissertation Abstracts.
137

Higher precision mass measurement via the boundary of many-body phase space

White, Craig Ian 26 March 2014 (has links)
We introduce a new method of mass measurement for particles in decay chains. The method relies upon performing a likelihood analysis on the phase space of the decay in its full dimensionality in a Lorentz-invariant formulation. This method is applicable for any decay chain, but we demonstrate it specifically in the case of a four-body final state decay in which one of the final particles is invisible. We directly compare our method to the edge and endpoint method and show that our new method can achieve higher precision with limited statistics. / text
138

Observation of disappearance of muon neutrinos in the NuMI beam

Pavlović, Žarko, 1977- 29 August 2008 (has links)
The Main Injector Neutrino Oscillation Search (MINOS) is a two detector long-baseline neutrino experiment designed to study the disappearance of muon neutrinos. MINOS will test the v[subscript mu] → v[subscript tau] oscillation hypothesis and measure precisely [Delta]m[superscript 2 subscript 23] and sin² 2[theta subscript 23] oscillation parameters. The source of neutrinos for MINOS experiment is Fermilab's Neutrinos at the Main Injector (NuMI) beamline. The energy spectrum and the composition of the beam is measured at two locations, one close to the source and the other 735 km downstream in the Soudan Mine Underground Laboratory in northern Minnesota. The precision measurement of the oscillation parameters requires an accurate prediction of the neutrino flux at the Far Detector. This thesis discusses the calculation of the neutrino flux at the Far Detector and its uncertainties. A technique that uses the Near Detector data to constrain the uncertainties in the calculation of the flux is described. The data corresponding to an exposure of 2.5×1020 protons on the NuMI target is presented and an energy dependent disappearance pattern predicted by neutrino oscillation hypotheses is observed in the Far Detector data. The fit to MINOS data, for given exposure, yields the best fit values for [Delta]m[superscript 2 subscript 23] and sin² 2[theta subscript 23] to be (2.38[superscript +0.20, subscript -0.16] x 10⁻³eV²/c⁴ and 1.00[subscript -0.08], respectively. / text
139

The weak charge of the proton: a search for physics beyond the standard model

MacEwan, Scott James 14 September 2015 (has links)
The Qweak experiment will provide the most precise determination of the proton’s weak charge Q^p_W by measuring the parity-violating asymmetry in elastic electron-proton scattering at low momentum transfer Q^2 = 0.0250 (GeV/c)^2. Qpw is related to the weak mixing angle sin^2\theta_W, a fundamental parameter of the standard model. A final measurement of the weak charge at the proposed 4% relative uncertainty is sensitive to certain types of new parity-violating physics beyond the standard model at the TeV mass-scale. Data were taken over a two year period beginning in 2010, using a custom apparatus installed in Hall-C at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia. A 180 microamp beam of longitudinally polarized electrons was accelerated to 1.165 GeV and then scattered from unpolarized protons in a liquid hydrogen target. The scattered electrons were then collimated and steered using a magnetic spectrometer onto a set of azimuthally symmetric quartz bar Cherenkov detectors. The performance of this main detector subsystem will be described in detail in this dissertation. A blinded analysis of Run-II, roughly 2/3 of the entire Qweak data set, resulted in an elastic ep asymmetry of -235.6 +/- 8.7 (Stat) +/- 9.3 (Syst.) +/- 39.3 (Blind) ppb. Using this value, the proton’s weak charge was calculated to be QpW = 0.0714 +/- 0.0093. This constitutes a 17% relative measurement, that will reduce to < 9% upon unblinding the asymmetry. This dissertation will provide the details that went into extracting both the parity-violating asymmetry and the weak charge of the proton. / October 2015
140

Particle-laden Turbulent Wall-bounded Flows in Moderately Complex Geometries

Noorani, Azad January 2015 (has links)
Wall-bounded turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. The complex nature of the carrier and the particulate phase is elevated to a higher level when introducing geometrical complexities such as curved walls. Realising such flows and dispersed phases poses challenging problems both from computational and also physical point of view. The present thesis addresses some of these issues by studying a coupled Eulerian–Lagrangian computational framework. The content of the thesis addresses both turbulent wall flows and coupled particle motion. In the first part, turbulent flow in straight pipes is simulated by means of direct numerical simulation (DNS) with the spectrally accurate code nek5000  to examine the Reynolds-number effect on turbulence statistics. The effect of the curvature to these canonical turbulent pipe flows is then added to generate Prandtl’s secondary motion of first kind. These configurations, as primary complex geometries in this study, are examined by means of statistical analysis to unfold the evolution of turbulence characteristics from a straight pipe. A fundamentally different Prandtl’s secondary motion of the second kind is also put to test by adding side-walls to a canonical turbulent channel flow and analysing the evolution of various statistical quantities with varying the duct width-to-height aspect ratios. Having obtained a characterisation of the turbulent flow in the geometries of bent pipes and ducts, the dispersion of small heavy particles is modelled in these configurations by means of point particles which are one-way coupled to the flow. For this purpose a parallel Lagrangian Particle Tracking (LPT) scheme is implemented in the spectral-element code nek5000 . Its numerical accuracy, parallel scalability and general performance in realistic situations is scrutinised. The analysis of the resulting particle fields shows that even a small amount of secondary motion has a profound impact on the particle phase dynamics and its concentration maps. For each of the aforementioned turbulent flow cases new and challenging questions have arisen to be addressed in the present research works. The goal of extending understanding of the particle dispersion in turbulent bent pipes and rectangular ducts are also achieved. / <p>QC 20151118</p>

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