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A measurement of the top quark's charge

Description: The top quark was discovered in 1995 at the Fermilab National Accelerator Laboratory (Fermilab). One way to confirm if the observed top quark is really the top quark posited in the Standard Model (SM) is to measure its electric charge. In the Standard Model the top quark is the isospin partner of the bottom quark and is expected to have a charge of +2/3. However, an alternative 'exotic' model has been proposed with a fourth generation exotic quark that has the same characteristics, such as mass, as our observed top but with a charge of -4/3. This thesis presents the first CDF measurement of the top quark's charge via its decay products, a W boson and a bottom quark, using {approx} 1 fb{sup -1} of data. The data were collected by the CDF detector from proton anti-proton (p{bar p}) collisions at {radical}s = 1.96 TeV at Fermilab. We classify events depending on the charges of the bottom quark and associated W boson and count the number of events which appear 'SM-like' or 'exotic-like' with a SM-like event decaying as t {yields} W{sup +}b and an exotic event as t {yields} W{sup -}b. We find the p-value under the Standard Model hypothesis to be 0:35 which is consistent with the Standard Model. We exclude the exotic quark hypothesis at an 81% confidence level, for which we have chosen a priori that the probability of incorrectly rejecting the SM would be 1%. The calculated Bayes Factor (BF) is 2 x Ln(BF)=8.54 which is interpreted as the data strongly favors the Standard Model over the exotic quark hypothesis.
Date: November 1, 2007
Creator: Unalan, Zeynep Gunay & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Measurement of the W + jet cross section at CDF

Description: A measurement of W {yields} ev + n-jet cross sections in p{bar p} collisions at {radical}s = 1.96 TeV using the Collider Detector at Fermilab in Run II is presented. The measurement is based on an integrated luminosity of 320 pb{sup -1}, and includes events with jet multiplicity from {ge} 1 to {ge} 4. In each jet multiplicity sample the differential and cumulative cross sections with respect to the transverse energy of the n{sup th}-leading jet are measured. For W + {ge} 2 jets the differential cross section with respect to the 2-leading jets invariant mass m{sub j{sub 1}j{sub 2}} and angular separation {Delta}R{sub j{sub 1}j{sub 2}} is also reported. The data are compared to predictions from Monte Carlo simulations.
Date: October 1, 2006
Creator: Messina, Andrea & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Optimization of accelerator parameters using normal form methods on high-order transfer maps

Description: Methods of analysis of the dynamics of ensembles of charged particles in collider rings are developed. The following problems are posed and solved using normal form transformations and other methods of perturbative nonlinear dynamics: (1) Optimization of the Tevatron dynamics: (a) Skew quadrupole correction of the dynamics of particles in the Tevatron in the presence of the systematic skew quadrupole errors in dipoles; (b) Calculation of the nonlinear tune shift with amplitude based on the results of measurements and the linear lattice information; (2) Optimization of the Muon Collider storage ring: (a) Computation and optimization of the dynamic aperture of the Muon Collider 50 x 50 GeV storage ring using higher order correctors; (b) 750 x 750 GeV Muon Collider storage ring lattice design matching the Tevatron footprint. The normal form coordinates have a very important advantage over the particle optical coordinates: if the transformation can be carried out successfully (general restrictions for that are not much stronger than the typical restrictions imposed on the behavior of the particles in the accelerator) then the motion in the new coordinates has a very clean representation allowing to extract more information about the dynamics of particles, and they are very convenient for the purposes of visualization. All the problem formulations include the derivation of the objective functions, which are later used in the optimization process using various optimization algorithms. Algorithms used to solve the problems are specific to collider rings, and applicable to similar problems arising on other machines of the same type. The details of the long-term behavior of the systems are studied to ensure the their stability for the desired number of turns. The algorithm of the normal form transformation is of great value for such problems as it gives much extra information about the disturbing factors. In addition to ...
Date: May 1, 2007
Creator: Snopok, Pavel & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Single top quark production at the Tevatron

Description: The Tevatron experiments D0 and CDF have found evidence for single top quark production, based on datasets between 0.9 fb{sup -1} and 2.2 fb{sup -1}. Several different multivariate techniques are used to extract the single top quark signal out of the large backgrounds. The cross section measurements are also used to provide the first direct measurement of the CKM matrix element |V{sub tb}|.
Date: May 1, 2008
Creator: Schwienhorst, Reinhard & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Search for single top quark production at D0 in Run II

Description: I present a comprehensive search for electroweak production of single top quarks in Run II at the Fermilab Tevatron at {radical}s =1.96TeV. Using 230 pb{sup -1} of data collected with the D0 experiment, searches for s-channel and t-channel single top quark production have been carried out in the electron+jets and muon+jets decay channels using secondary-vertex b-quark tagging to select signal-like events. A binned likelihood has been constructed from the outputs of neural networks in order to maximize the sensitivity to single top quark production. No evidence for a single top quark signal is found. However, the 95% confidence level upper limits on the production cross section of 6.4 pb in the s-channel and 5.0 pb in the t-channel are improvements over previous limits by a factor of two and are approaching the cross section region predicted by the standard model.
Date: April 1, 2005
Creator: Schwienhorst, Reinhard & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Measurement of the Diphoton Differential Cross Section in p anti-p Collisions at s**(1/2) = 1.96-TeV

Description: The diphoton differential cross-section as a function of mass up to 300 GeV/c{sup 2}, q{sub T} up to 100 GeV/c, and opening angle over a range of 0 to {pi} radians is measured. The measurement is performed using 1046.19 pb{sup -1} of data collected at Fermi National Accelerator Laboratory using the D0 detector. This analysis considers all direct diphoton states but attempts to suppress contributions due to fragmentation.
Date: January 1, 2007
Creator: Dyer, Joshua Marc & U., /Michigan State
Partner: UNT Libraries Government Documents Department

The inclusive jet cross-section in proton anti-proton collisions at s**(1/2) = 1.96-TeV using the MidPoint jet algorithm

Description: The following work presents a preliminary measurement of the inclusive jet cross section for jet transverse momenta from 61 to 620 GeV in the rapidity range 0.1 < |Y| < 0.7. The result is based on 218 pb{sup -1} of data collected by the CDF detector at the Fermi National Accelerator Lab. The data are consistent with NLO pQCD predictions based on the CTEQ6.1 parton distribution functions.
Date: April 1, 2005
Creator: Flanagan, Gene U. & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Uncovering the single top: observation of electroweak top quark production

Description: The top quark is generally produced in quark and anti-quark pairs. However, the Standard Model also predicts the production of only one top quark which is mediated by the electroweak interaction, known as 'Single Top'. Single Top quark production is important because it provides a unique and direct way to measure the CKM matrix element V{sub tb}, and can be used to explore physics possibilities beyond the Standard Model predictions. This dissertation presents the results of the observation of Single Top using 2.3 fb{sup -1} of Data collected with the D0 detector at the Fermilab Tevatron collider. The analysis includes the Single Top muon+jets and electron+jets final states and employs Boosted Decision Tress as a method to separate the signal from the background. The resulting Single Top cross section measurement is: (1) {sigma}(p{bar p} {yields} tb + X, tqb + X) = 3.74{sub -0.74}{sup +0.95} pb, where the errors include both statistical and systematic uncertainties. The probability to measure a cross section at this value or higher in the absence of signal is p = 1.9 x 10{sup -6}. This corresponds to a standard deviation Gaussian equivalence of 4.6. When combining this result with two other analysis methods, the resulting cross section measurement is: (2) {sigma}(p{bar p} {yields} tb + X, tqb + X) = 3.94 {+-} 0.88 pb, and the corresponding measurement significance is 5.0 standard deviations.
Date: August 1, 2009
Creator: Benitez, Jorge Armando & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Single top quark production and Vtb at the Tevatron

Description: Single top quark production via the electroweak interaction was observed by the D0 and CDF collaborations at the Tevatron proton-antiproton collider at Fermilab. Multivariate analysis techniques are employed to extract the small single top quark signal. The combined Tevatron cross section is 2.76{sub -0.47}{sup +0.58} pb. This corresponds to a lower limit on the CKM matrix element |V{sub tb}| of 0.77. Also reported are measurements of the t-channel cross section, the top quark polarization in single top quark events, and limits on gluon-quark flavor-changing neutral currents and W{prime} boson production.
Date: September 1, 2010
Creator: Schwienhorst, Reinhard & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Standard Model Higgs searches at the Tevatron

Description: We report results of searches for the Standard Model Higgs Boson at the Fermilab Tevatron using up to 5.4 fb{sup -1} of data taken with the CDF and D0 detectors. There is no significant excess in the mass range of interest and the experiments set upper limits on the Higgs boson production cross section, including an exclusion of the Standard Model Higgs in the mass range 162-166 GeV.
Date: April 1, 2010
Creator: Herner, Kenneth & U., /Michigan
Partner: UNT Libraries Government Documents Department

Search for neutral supersymmetric Higgs bosons in \boldmath{$p\bar{p}$} collisions at \boldmath{$\sqrt{s}$} = 1.96 TeV

Description: We report results of searches for neutral supersymmetric Higgs Bosons in up to 2.7 fb{sup -1} of data collected with the D0 detector at the Fermilab Tevatron. The final states include muons, taus, and jets from the decay of b hadrons. The searches observe no significant excess and set upper limits on neutral Higgs production cross sections. The limits are also translated into exclusions of MSSM parameter space.
Date: August 1, 2009
Creator: Herner, Ken & U., /Michigan
Partner: UNT Libraries Government Documents Department

Measurement of the t anti-t production cross section in p anti-p collisions at s**(1/2) = 1.96-TeV

Description: The direct observation of the top quark was first achieved at the Tevatron proton anti-proton collider at Fermilab. This discovery completed the third generation quark sector where the top quark is expected to accompany the bottom quark in the weak isospin doublet. This dissertation discusses the experimental verification of the production cross section as predicted by the Standard Model. A measurement of the t{bar t} production cross section using 107.9 pb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV collected with the Collider Detector at Fermilab between March of 2003 and June of 2003 is presented. The measurement focuses on the t{bar t} production in the ''lepton plus jets'' final state in which one of the W bosons from the t{bar t} decay subsequently decays leptonically to an electron or a muon, and the other decays hadronically. The B-tagging technique which utilizes the precision silicon detector tracking is used to enhance the signal for t{bar t} events relative to the background through identification of the bottom quark from its measurable lifetime. The t{bar t} production cross section is measured to be {sigma}{sub t{bar t}} = 4.5 {+-} 1.4(stat) {+-} 0.8(sys) pb.
Date: February 1, 2004
Creator: Ray, Heather Lynn & U., /Michigan
Partner: UNT Libraries Government Documents Department

The Production Cross Sections of the Weak Vector Bosons in Proton Antiproton Collisions at s**(1/2) = 1.96-TeV and a Measurement of the W Boson Decay Width

Description: The theory that describes the fundamental particle interactions is called the Standard Model, which is a gauge field theory that comprises the Glashow-Weinberg-Salam model [1, 2, 3] of the weak and electromagnetic interactions and quantum chromodynamics (QCD) [4, 5, 6], the theory of the strong interactions. The discovery of the W [7, 8] and Z [9, 10] bosons in 1983 by the UA1 and UA2 collaborations at the CERN p{bar p} collider provided a direct confirmation of the unification of the weak and electromagnetic interactions. Since then, many experiments have refined our understanding of the characteristics of the W and Z bosons.
Date: April 1, 2004
Creator: Varganov, Alexei Valerievich & U., /Michigan
Partner: UNT Libraries Government Documents Department

The D0 run II trigger system

Description: The D0 detector at the Fermilab Tevatron was upgraded for Run II. This upgrade included improvements to the trigger system in order to be able to handle the increased Tevatron luminosity and higher bunch crossing rates compared to Run I. The D0 Run II trigger is a highly exible system to select events to be written to tape from an initial interaction rate of about 2.5 MHz. This is done in a three-tier pipelined, buffered system. The first tier (level 1) processes fast detector pick-off signals in a hardware/firmware based system to reduce the event rate to about 1. 5kHz. The second tier (level 2) uses information from level 1 and forms simple Physics objects to reduce the rate to about 850 Hz. The third tier (level 3) uses full detector readout and event reconstruction on a filter farm to reduce the rate to 20-30 Hz. The D0 trigger menu contains a wide variety of triggers. While the emphasis is on triggering on generic lepton and jet final states, there are also trigger terms for specific final state signatures. In this document we describe the D0 trigger system as it was implemented and is currently operating in Run II.
Date: November 1, 2004
Creator: Schwienhorst, Reinhard & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Measurements of the top - anti-top Production Cross Section at s**(1/2) = 1.96-TeV and Top Mass in the Dielectron Channel

Description: The first measurement of the top-antitop production cross section in proton-antiproton collisions at {radical}s = 1.96 TeV using 243 pb{sup -1} of data collected with the D0 detector at Fermilab is presented. In this analysis, only the dielectron final state is considered. Five events are observed, and 0.93 background events are expected. The measured cross section, after accounting for the expected branching ratio to the dielectron channel, is {sigma}{sub t{bar t}} = 14.9{sub -7.0}{sup +9.4}(stat){sub -1.8}{sup +2.5}(syst) {+-} 1.0 (lumi) pb, which agrees with the predicted cross section for top quarks with a mass of 175 GeV. In addition, a first-pass at a measurement of the top mass using the neutrino-weighting method is presented. This measurement is also performed in the dielectron channel using the five events observed in the cross section measurement.
Date: May 1, 2005
Creator: Kozminski, Joseph Francis & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Search for single top production at the Tevatron

Description: Searches for the electroweak production of single top quarks have been started at the Fermilab Tevatron proton-antiproton collider using Run II data by both the D0 and CDF collaborations. Using a dataset of approximately 160pb{sup -1}, neither experiment finds evidence for Single Top production and sets 95% C.L. upper limits on the production cross section. The D0 limits are 19pb on the s-channel production, 25pb on the t-channel production, and 23pb on the combined s+t-channel production. The CDF limits are 8.5pb on the t-channel production and 13.7pb on the combined s+t-channel production.
Date: November 1, 2004
Creator: Schwienhorst, Reinhard & U., /Michigan State
Partner: UNT Libraries Government Documents Department

High Transverse Momentum Direct Photon Production at Fermilab Fixed-Target Energies

Description: This thesis describes a study of the production of high transverse momentum direct photons and {pi}{sup 0} mesons by proton beams at 530 and 800 GeV/c and {pi}{sup -} beams at 515 GeV/c incident on beryllium, copper, and liquid hydrogen targets. The data were collected by Fermilab experiment E706 during the 1990 and 1991-92 fixed target runs. The apparatus included a large, finely segmented lead and liquid argon electromagnetic calorimeter and a charged particle spectrometer featuring silicon strip detectors in the target region and proportional wire chambers and drift tubes downstream of a large aperture analysis magnet. The inclusive cross sections are presented as functions of transverse momentum and rapidity. The measurements are compared with next-to-leading order perturbative QCD calculations and to results from previous experiments.
Date: May 1, 2005
Creator: Apanasevich, Leonard & U., /Michigan State
Partner: UNT Libraries Government Documents Department

Measurement of B(t -> Wb)/B(t -> Wq)

Description: The authors measure the ratio R = B(t {yields} Wb)/B(t {yields} Wq) in top-quark decays at CDF. R is determined from the relative rates of identified b jets in t{bar t} decays reconstructed both in the lepton-plus-jets and dilepton final states. They obtain R > 0.62 at the 95% CL, consistent with Standard Model expectations.
Date: December 1, 2004
Creator: Tecchio, Monica & U., /Michigan
Partner: UNT Libraries Government Documents Department

Observation of Single Top Quark Production with the D0 Detector

Description: We report on the observation of single top quark production by the D0 collaboration using a dataset of 2.3 fb{sup -1} collected at the Fermilab Tevatron p{bar p} collider. Several multivariate techniques are combined to separate the single top signal from backgrounds. The measured single top cross section is {sigma}{sub tb+tqb} = 3.94 {+-} 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.9 x 10{sup -7}, corresponding to a 5.0 standard deviation significance for the presence of signal. The lower limit at the 95% C.L. on the CKM matrix element V{sub tb} is |V{sub tb}| > 0.78. A separate measurement of the t-channel cross section gives {sigma}{sub tqb} = 3.14{sub -0.80}{sup +0.94} pb.
Date: August 1, 2009
Creator: Schwienhorst, Reinhard; collaboration, for the D0 & U., /Michigan State
Partner: UNT Libraries Government Documents Department

A GMBCG Galaxy Cluster Catalog of 55,424 Rich Clusters from SDSS DR7

Description: We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.
Date: August 22, 2011
Creator: Hao, Jiangang; /Fermilab; McKay, Timothy A.; U., /Michigan; Koester, Benjamin P.; U., /Chicago et al.
Partner: UNT Libraries Government Documents Department

Evolutionary algorithm for the neutrino factory front end design

Description: The Neutrino Factory is an important tool in the long-term neutrino physics program. Substantial effort is put internationally into designing this facility in order to achieve desired performance within the allotted budget. This accelerator is a secondary beam machine: neutrinos are produced by means of the decay of muons. Muons, in turn, are produced by the decay of pions, produced by hitting the target by a beam of accelerated protons suitable for acceleration. Due to the physics of this process, extra conditioning of the pion beam coming from the target is needed in order to effectively perform subsequent acceleration. The subsystem of the Neutrino Factory that performs this conditioning is called Front End, its main performance characteristic is the number of the produced muons.
Date: January 1, 2009
Creator: Poklonskiy, Alexey A.; U., /Michigan State; Neuffer, David & /Fermilab
Partner: UNT Libraries Government Documents Department

Muon cooling in a quadrupole magnet channel

Description: As discussed before,[1] a cooling channel using quadrupole magnets in a FODO transport channel can be used for initial cooling of muons. In the present note we discuss this possibility of a FODO focusing channel for cooling, and we present ICOOL simulations of muon cooling within a FODO channel. We explore a 1.5m cell-length cooling channel that could be used for the initial transverse cooling stage of a muon collider or neutrino factory.
Date: October 1, 2007
Creator: Neuffer, David; /Fermilab; Poklonskiy, A. & U., /Michigan State
Partner: UNT Libraries Government Documents Department