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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.
11

Inclusive Jet Production Studies at the Tevatron using the CDF Detector

Norniella Francisco, Olga 30 March 2007 (has links)
QCD es una teoría que gobierna la interacción fuerte entre quarks y gluones dentro de los hadrones, por ejemplo, protones y neutrones. Esta teoría tiene dos características: libertad asintótica y color confinamiento. La dependencia de la constante de acoplamiento con la escala es tal que esta decrece con la distancia entre partones. Esto permite realizar precisos cálculos teóricos a una gran escala de energía usando teoría de perturbaciones (pQCD). Además, la fuerza de la interacción incrementa con la distancia entre partones y gluones obligando que estos estén confinados en hadrones.En el acelerador Tevatron, protones y antiprotones colisionan a una alta energía. En estas colisiones se producen jets de hadrones colimados en la misma dirección de los quarks y gluones que han colisionado. La medida de la sección eficaz de producción de jets centrales constituye una prueba de las predicciones de pQCD en más de ocho órdenes de magnitud. Además la medida también es sensible a la distribución de los partones dentro del proton (PDFs). Medidas de la producción de jets a grandes rapidititis son importantes porque ayudan a restringir la incertidumbre en esas distribuciones de los partones en una región donde no se espera señal de nueva física. Esta tesis presenta la medida de producción de jets usando datos recogidos por el experimento CDF, uno de los detectores que estudia las colisiones en Tevatron. La medida esta hecha con un algoritmo muy preciso para buscar jets, relativamente nuevo en colisionadores hadrónicos. La medida esta comparada con predicciones de pQCD, donde los efectos de efectos no-perturbativos han sido incluidos. Los resultados demuestran que hay un excelente acuerdo entre la medida y la teoría, no mostrando señal de nueva física. Además, las incertidumbre es la medida son mas pequeñas que la teoría, cosa que indica que estas medidas pueden ser usadas para restringir las PDFs. / QCD is the gauge theory that governs the strong interactions between quarks and gluons inside hadrons like, for example, protons and neutrons. It shows two well established characteristics, related to the non-abelian nature of the theory, that dominate its phenomenology: asymptotic freedom and color confinement. The dependence of the strong coupling with the hard scale is such that it decreases with decreasing the distance between partons. This allows performing precise theoretical calculations at large energy transfer using perturbative QCD (pQCD). In the other hand, the strength of the interaction increases with the distance between partons and thus colored quarks and gluons are forced to be confined inside colorless hadrons.At the Tevatron at Fermilab, protons and antiprotons collide at very high energy. In those collisions, collimated jets of hadrons are produced along the direction of struck quarks and gluons in the final state. The measurement of the inclusive jet production cross section provides a stringent test of pQCD predictions over almost nine orders of magnitude. In addition, the measurement is sensitive to the parton distribution in the proton (PDFs). Jet measurements at large rapidities are important because they constrain the gluon density in a region where no effect from new physics is expected.This PhD. Thesis presents a measurement of the inclusive jet production cross section using the new data collected by the CDF experiment in Run II, one of the detectors at Tevatron. The longitudinally invariant kT algorithm has been used in order to search for jets in the final state. The measurement is compared to pQCD NLO calculations where non-perturbative effects from the underlying event and the fragmentation of partons into jets of hadrons have been taken into account. The results show an excellent agreement between the measurements and the theory, without presenting signal for new physics. In addition the systematic uncertainties in the measurements are smaller than in the theory, indicating that these measurements can be used to constrain the PDFs.
12

A measurement of top anti-top quark pair production cross section in proton anti-proton collisions at a center-of-mass energy of 1.96 TeV

Chung, Jongyoung January 2003 (has links)
No description available.
13

Precisionsbevattning i praktiken : En fallbaserad validering av satellitanalys för markfuktighetsdata

Borg, Maja January 2024 (has links)
Agriculture faces significant challenges with current climate change and a growing global population. Increasing dry periods, even in Sweden, require increased field irrigation to secure harvests while water availability decreases. Research in remote sensing has led to significant technological advancements where soil moisture can now be detected with precision at 100x100 meters. This study aims to evaluate how well satellite analysis of soil moisture aligns with field experiments and its usefulness for irrigation decisions. Through the collection and analysis of data from both field measurements and satellites, the agreement between these has been examined where statistical measures such as NNSE, RMSE, and MAE have been used. A challenge with satellite analysis is its limitation to measuring soil moisture only in the top layer (3-5 cm) of the soil, which does not estimate the water content in the root zone required for irrigation decisions. To address this, the cumulative function matching method (CDF-method) was used to estimate the water content in the root zone based on satellite measurements of the top soil layer. The results show that satellite data aligns with field measurements for various locations in Sweden, with NNSE values between 0.08-0.61 and an accuracy (MAE) of 4.51-6.99 % water content. Furthermore, the results indicate that water content in the root zone can be estimated from surface soil moisture using the CDF matching method with an accuracy of 1.28-6.41 %. However, this method requires cross-validation in the field where the estimation is to be performed, and the use of satellite analysis for irrigation decisions is limited to the field level. To effectively utilize satellite analysis as a global decision support, methods for estimating water content in the root zone need to be developed to be more applicable for the different soil types.
14

Measurement of the Top Quark Pair Production Cross-section in the Dilepton Channel using Lepton plus Track Selection and Identified b-jets

Spreitzer, Teresa 01 April 2010 (has links)
Using 1.0 fb^{-1} of data collected by the Collider Detector at Fermilab (CDF) from Run II of the Fermilab Tevatron, we measure the top-antitop production cross-section in events with two leptons, significant missing transverse energy, and at least jets, at least one of which is identified as a b-jet. As the Run II dataset grows, more stringent tests of Standard Model predictions for the top quark sector are becoming possible. The dilepton channel, where both top quarks decay t-> W b ->l nu b, is of particular interest due to its high purity. Use of an isolated track as the second lepton significantly increases the dilepton acceptance, at the price of some increase in background, particularly from W + jets events where one of the jets is identified as a lepton. To control the increase in background we add to the event selection the requirement that at least one of the jets be identified as a b-jet, reducing the background contribution from all sources. Assuming a branching ratio of BR(W->l nu) = 10.8% and a top mass of m_top = 175 GeV/c^{2} the measured cross-section is sigma = (10.5 +/- 1.8 stat. +/- 0.8 syst. +/- 0.6 lumi.) pb.
15

Measurement of the Top Quark Pair Production Cross-section in the Dilepton Channel using Lepton plus Track Selection and Identified b-jets

Spreitzer, Teresa 01 April 2010 (has links)
Using 1.0 fb^{-1} of data collected by the Collider Detector at Fermilab (CDF) from Run II of the Fermilab Tevatron, we measure the top-antitop production cross-section in events with two leptons, significant missing transverse energy, and at least jets, at least one of which is identified as a b-jet. As the Run II dataset grows, more stringent tests of Standard Model predictions for the top quark sector are becoming possible. The dilepton channel, where both top quarks decay t-> W b ->l nu b, is of particular interest due to its high purity. Use of an isolated track as the second lepton significantly increases the dilepton acceptance, at the price of some increase in background, particularly from W + jets events where one of the jets is identified as a lepton. To control the increase in background we add to the event selection the requirement that at least one of the jets be identified as a b-jet, reducing the background contribution from all sources. Assuming a branching ratio of BR(W->l nu) = 10.8% and a top mass of m_top = 175 GeV/c^{2} the measured cross-section is sigma = (10.5 +/- 1.8 stat. +/- 0.8 syst. +/- 0.6 lumi.) pb.
16

An Improved W Boson Mass Measurement using the Collider Detector at Fermilab

Zeng, Yu January 2012 (has links)
<p>The mass of the $W$ boson is one of the most important parameters in the </p><p>Standard Model. A precise measurement of the $W$ boson mass, together </p><p>with a precise measurement of the top quark mass, can constrain the </p><p>mass of the undiscovered Higgs boson within the Standard Model </p><p>framework or give a hint for physics beyond the Standard Model. </p><p>This dissertation describes a measurement of the $W$ boson mass </p><p> through its decay into a muon and a neutrino using </p><p> $\approx$ 2.2 fb$^{-1}$ of $\sqrt{s} = 1.96$ TeV $p\bar{p}$ data taken </p><p> with the CDF II detector at Fermilab. We measure the $W$ boson mass </p><p> to be ($80.374 \pm 0.015_{\rm stat.} \pm 0.016_{\rm syst.}$) </p><p> GeV/c$^2$. This result, when combined with the $W$ mass </p><p> measurement in the electron channel, leads to the single most </p><p> precise $m_W$ value and greatly constrains the possible mass </p><p> range of the undiscovered Higgs boson.</p> / Dissertation
17

Search for heavy, long-lived particles that decay to photons in ppbar collisions at sqrt(s)=1.96 tev

Wagner, Peter 02 June 2009 (has links)
This dissertation presents the results of the first search for heavy, neutral, longlived particles that decay to photons at a hadron collider. We use a sample of +jet+missing transverse energy events in p¯p collisions at ps = 1.96 TeV taken with the Collider Detector at Fermilab. Candidate events are selected based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed. The final result is that we find 2 events, using 570±34 pb−1 of data collected during 2004-2005 at the Fermilab Tevatron, consistent with the background estimate of 1.3±0.7 events. While our search strategy does not rely on model-specific dynamics, we interpret this result in terms of cross section limits in a supersymmetric model with e01! eG and set a world-best e01 mass reach of 101 GeV/c2 at e = 5 ns. We can exclude any +jet+missing transverse energy signal that would produce more than 5.5 events.
18

Search for Supersymmetry Using Diphoton Events in Proton-Antiproton Collisions at a Center of Mass Energy of 1.96 TeV

Lee, Eun Sin 2010 May 1900 (has links)
This dissertation presents the results of a search for supersymmetry in protonantiproton 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 nal 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 nd no events using 2.6 fb-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 gaugemediated supersymmetry model with e 01 ! eG, where the e 01 and eG are the lightest neutralino and the gravitino (the lightest supersymmetric particle), respectively. We set limits on models as a function of the e 01 mass and lifetime, producing the world's most sensitive search for e 01by excluding masses up to 149 GeV=c2 for e 01 lifetimes much less than 1 ns.
19

Statistical and Economic Implications Associated with Precision of Administering Weight-based Medication in Cattle

Olvera, Isaac Daniel 2010 December 1900 (has links)
Metaphylactic treatment of incoming feedlot cattle is a common preventative action against bovine respiratory disease (BRD). Cattle are dosed based on estimated or actual lot average weights, rather than on an individual basis, to reduce initial processing time. There has been limited research conducted on the effects of accurate weight- based dosing in feedlot cattle. The objective of this study was to evaluate the economic effects of precision weight- based dosing of cattle as compared to dosing the lot average or lot averages plus 50 lb and minus 50 lb. An economic model was created and stochastic simulations performed to evaluate potential outcomes of different dosing scenarios. Economic analyses of the effects of precision weight-based dosing were conducted using SIMETAR© to determine the stochastic dominance and economic effects of different dosing regimens. Data were obtained from a commercial feedlot for different lots of cattle where individual animal weights were available; for this analysis the minimum lot size was 30 animals, and the maximum lot size was 126 animals. Within lots, individual weight deviations were calculated from the lot mean, the lot mean was rounded up to the nearest 50 lb increment or down to the nearest 50 lb increment to represent mild overestimation and mild underestimation, respectively. Tulathromycin (Draxxin®, Pfizer Animal Health, New York, NY), an antimicrobial commonly prescribed for treatment of bovine respiratory disease, was used to illustrate the impacts of uniform dosing versus exact dosing per body weight. Based on the dilution space method used to evaluate time of drug effectiveness, it was estimated that Draxxin® administered at the recommended dosage to cattle weighing between 500 and 1000 lb should be provided with 191 hours (7.96 days) of protection from pneumonia-causing bacteria. Due to the pharmacokinetic properties of Draxxin®, an animal that is administered half the recommended dose is only protected from pneumonia-causing bacteria for 8 hours, which is 4.2 percent of the coverage time of the proper dose. This limits the effectiveness of the prescribed treatment to fully administer therapeutic treatment. In all cases, the correct weight-based dosing strategy cost less than any other dosing technique. Overall, dosing all cattle at the lot average weight costs $6.04 per animal more than dosing at the exact, correct dose. Dosing all animals at the lot average weight plus 50 lb costs $6.24 per animal more; dosing all animals at lot average minus 50 lb costs $4.01 per animal more. The use of individual animal weights to determine per head dosing of Draxxin® is more cost effective than using lot averages. This concept would appear to extend to all weight-based pharmaceutical products in general, and should be considered a necessary management strategy.
20

A Simulation of LFM Pulse-Doppler Radar and an Application of Cohen-Daubechies-Feauveau Wavelets in CFAR Detection

Wright, Aaron Joshua 08 December 2017 (has links)
This thesis presents a simulation of an LFM pulse-Doppler radar for surface-to-air applications and compares the performance of multiple CFAR detectors in processing the resulting range-Doppler maps. Each CFAR detector is reviewed and simulated. Their effectiveness in reducing target masking is analyzed. In addition, a new CFAR detector, the RDWT-CA-CFAR detector, is developed that uses the CDF 5/3 wavelet to decompose the range-data of the range-Doppler map along the range dimension and filter the target data from the reference cells, as a means to reduce or eliminate target masking. The QccPack library is used to perform RDWT functions. It is shown that the novel RDWT-CA-CFAR detector performs better in processing range-Doppler maps when compared to the other robust CFAR detectors covered in this project.

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