Download or read book Measurement of the Top Quark Mass Using Dilepton Events and a Neutrino Weighting Algorithm with the D Experiment at the Tevatron Run II written by Jörg Meyer and published by . This book was released on 2007 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the Top Quark Mass Using Dilepton Events and a Neutrino Weighting Algorithm with the D0 Experiment at the Tevatron Run II written by and published by . This book was released on 2007 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Elementary particle physics raises questions that are several thousand years old. What are the fundamental components of matter and how do they interact? These questions are linked to the question of what happened in the very first moments after the creation of the universe. Modern physics systematically tests nature to find answers to these and other fundamental questions. Precise theories are developed that describe various phenomena and at the same time are reduced to a few basic principals of nature. Simplification and reduction have always been guiding concepts of physics. The interplay between experimental data and theoretical descriptions led to the Standard Model of elementary particle physics. It summarizes the laws of nature and is one of most precise descriptions of nature achieved by mankind. Despite the great success of the Standard Model it is not the ultimate theory of everything. Models beyond the Standard Model try to unify all interactions in one grand unified theory. The number of free parameters is attempted to be reduced. Gravity is attempted to be incorporated. Extensions to the Standard Model like supersymmetry address the so-called hierarchy problem. Precision measurements are the key for searches of new particles and new physics. A powerful tool of experimental particle physics are particle accelerators. They provide tests of the Standard Model at smallest scales. New particles are produced and their properties are investigated. In 1995 the heaviest known elementary particle, called top quark, has been discovered at Fermilab. It differs from all other lighter quarks due to the high mass and very short lifetime. This makes the top quark special and an interesting object to be studied. A rich program of top physics at Fermilab investigates whether the top quark is really the particle as described by the Standard Model. The top quark mass is a free parameter of the theory that has been measured precisely. This thesis presents a precise measurement of the top quark mass by the D0 experiment at Fermilab in the dilepton final states. The comparison of the measured top quark masses in different final states allows an important consistency check of the Standard Model. Inconsistent results would be a clear hint of a misinterpretation of the analyzed data set. With the exception of the Higgs boson, all particles predicted by the Standard Model have been found. The search for the Higgs boson is one of the main focuses in high energy physics. The theory section will discuss the close relationship between the physics of the Higgs boson and the top quark.
Download or read book Measurement of the Mass of the Top Quark in Dilepton Final States with the D0 Detector written by Oleg Brandt and published by . This book was released on 2006 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the Standard Model (SM) the top quark mass is a fundamental parameter. Its precise measurement is important to test the self-consistency of the SM. Additionally, it offers sensitivity to New Physics beyond the Standard Model. In proton anti-proton collisions at a centre-of-mass energy of {radical}s = 1.96 TeV t{bar t} quarks are pair-produced, each decaying into a W boson and a b quark. In the dilepton channel both W bosons decay leptonically. Because of the presence of two neutrinos in the final state the kinematics are underconstrained. A so-called Neutrino Weighting algorithm is used to calculate a weight for the consistency of a hypothesized top quark mass with the event kinematics. To render the problem solvable, the pseudorapidities of the neutrinos are assumed. The Maximum Method, which takes the maximum to the weight distribution as input to infer the top quark mass, is applied to approximately 370 pb{sup -1} of Run-II data, recorded by the D0 experiment at the Tevatron. The e{mu}-channel of the 835 pb{sup -1} dataset is analyzed.
Download or read book Measurement of the Top Quark Mass in Dilepton Final States with the Neutrino Weighting Method written by and published by . This book was released on 2012 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the heaviest fundamental particle observed to date. The mass of the top quark is a free parameter in the Standard Model (SM). A precise measurement of its mass is particularly important as it sets an indirect constraint on the mass of the Higgs boson. It is also a useful constraint on contributions from physics beyond the SM and may play a fundamental role in the electroweak symmetry breaking mechanism. I present a measurement of the top quark mass in the dilepton channel using the Neutrino Weighting Method. The data sample corresponds to an integrated luminosity of 4.3 fb-1 of p$\bar{p}$ collisions at Tevatron with √s = 1.96 TeV, collected with the DØ detector. Kinematically under-constrained dilepton events are analyzed by integrating over neutrino rapidity. Weight distributions of t$\bar{t}$ signal and background are produced as a function of the top quark mass for different top quark mass hypotheses. The measurement is performed by constructing templates from the moments of the weight distributions and input top quark mass, followed by a subsequent likelihood t to data. The dominant systematic uncertainties from jet energy calibration is reduced by using a correction from `+jets channel. To replicate the quark avor dependence of the jet response in data, jets in the simulated events are additionally corrected. The result is combined with our preceding measurement on 1 fb-1 and yields mt = 174.0± 2.4 (stat.) ±1.4 (syst.) GeV.
Download or read book Measurement of M top Via Neutrino Weighting in the Dilepton Decay Channels at written by Jeffrey W. Temple and published by . This book was released on 2006 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the top quark mass from dilepton decay channels is presented, using approximately 360 pb-1 of data colleced by the D0 experiment at Fermilab. The mass is measured from a total of 21 candidate dilepton events, using the neutrino weighting scheme. The measured mass is found to be 175.6+/-10.7(stat.)+/-6.0(syst.) GeV. This result is in good agreement with the current world average of the top quark mass.
Download or read book Precise Measurement of the Top Quark Mass in Dilepton Decays Using Optimized Neutrino Weighting written by and published by . This book was released on 2015 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: We measure the top quark mass in dilepton final states of tt¯ events in pp¯ collisions at √s= 1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb-1 at the Fermilab Tevatron Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. Furthermore, we improve the calibration of jet energies using the calibration determined in tt¯ → lepton + jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. As a result, the measured top quark mass is mt = 173.32±1.36(stat)±0.85(syst) GeV.
Download or read book Measurement of the Top Quark Mass in the Dilepton Channel Using the Neutrino Weighting Algorithm at CDF II written by Simon Sabik and published by . This book was released on 2006 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: We measure the top quark mass using approximately 359 pb-1 of data from pp− collisions at s = 1.96 GeV at CDF Run II. We select tt− candidates that are consistent with two W bosons decaying to a charged lepton and a neutrino following tt− & rarr; W+W-bb− & rarr; l+l- nn & d1; bb−. Only one of the two charged leptons is required to be identified as an electron or a muon candidate, while the other is simply a well measured track. We use a neutrino weighting algorithm which weighs each possibility of neutrino direction to reconstruct a top quark mass in each event. We compare the resulting distribution to Monte Carlo templates to obtain a top quark mass of 170.8+6.9-6.5 (stat) +/- 4.6 (syst) GeV/c 2.
Download or read book Top mass Measurements from written by and published by . This book was released on 2009 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present three recent analyses (Abstracts 169, 170 and 174) of the mass of the top quark (M{sub t}) using top-antitop candidate events collected by the D0 experiment at the Fermilab Tevatron Collider: (i) a 3.6 events/fb sample of data in the lepton+jets channel analyzed to extract a precision value of M{sub t} using the 'Matrix-Element' (ME) method, wherein each event probability is calculated from the differential production cross section as a function of M{sub t} and the overall jet energy scale, with the latter constrained by the two jets from W decay into q(prime){bar q}, (ii) a first measurement of the mass difference between top and antitop quarks as a check of CPT invariance in the quark sector, also based on the ME method in lepton+jets channels, and corresponding to a 1 event/fb data sample, and (iii) measurements of M{sub t} in dilepton final states (updated to 3.6 events/fb), based on 'matrix' weighting, 'neutrino' weighting and the ME method, which rely, respectively, on the likelihood of observing the events in data for a range of assumed M{sub t} values, distributions generated from event weights that compare calculated and reconstructed missing transverse energies, and event probabilities based on the leading-order differential cross section as a function of assumed M{sub t}. In addition, we provide a combination of recent top-mass measurements from D0.
Download or read book A Precise Measurement of the Top Quark Mass in Dilepton Final States Using 9 7 Fb 1 of D O Run II Data written by and published by . This book was released on 2015 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is a very special fundamental particle in the Standard Model (SM) mainly due to its heavy mass. The top quark has extremely short lifetime and decays before hadronization. This reduces the complexity for the measurement of its mass. The top quark couples very strongly to the Higgs boson since the fermion-Higgs Yukawa coupling linearly depends on the fermion's mass. Therefore, the top quark is also heavily involved in Higgs production and related study. A precise measurement of the top quark mass is very important, as it allows for self-consistency check of the SM, and also gives a insight about the stability of our universe in the SM context. This dissertation presents my work on the measurement of the top quark mass in dilepton final states of t$\bar{t}$ events in p$\bar{p}$ collisions at √s = 1.96 TeV, using the full DØ Run II data corresponding to an integrated luminosity of 9.7 fb-1 at the Fermilab Tevatron. I extracted the top quark mass by reconstructing event kinematics, and integrating over expected neutrino rapidity distributions to obtain solutions over a scanned range of top quark mass hypotheses. The analysis features a comprehensive optimization that I made to minimize the expected statistical uncertainty. I also improve the calibration of jets in dilepton events by using the calibration determined in t$\bar{t}$ → lepton+jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured mass is 173.11 ± 1.34(stat)+0.83 -0.72(sys) GeV .
Download or read book Measurement of the Top Quark Mass in the Dilepton Channel written by and published by . This book was released on 2006 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the top quark mass in the dilepton channel based on approximately 370 pb−1 of data collected by the D0 experiment during Run II of the Fermilab Tevatron collider. We employ two different methods to extract the top quark mass. We show that both methods yield consistent results using ensemble tests of events generated with the D0 Monte Carlo simulation. We combine the results from the two methods to obtain a top quark mass m{sub t} = 178.1 ± 8.2 GeV. The statistical uncertainty is 6.7 GeV and the systematic uncertainty is 4.8 GeV.
Download or read book Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method written by and published by . This book was released on 2008 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark, discovered in 1995 by the CDF and D0 experiments at the Fermilab Tevatron Collider, is the heaviest known fundamental particle. The precise knowledge of its mass yields important constraints on the mass of the yet-unobserved Higgs boson and allows to probe for physics beyond the Standard Model. The first measurement of the top quark mass in the dilepton channel with the Matrix Element method at the D0 experiment is presented. After a short description of the experimental environment and the reconstruction chain from hits in the detector to physical objects, a detailed review of the Matrix Element method is given. The Matrix Element method is based on the likelihood to observe a given event under the assumption of the quantity to be measured, e.g. the mass of the top quark. The method has undergone significant modifications and improvements compared to previous measurements in the lepton+jets channel: the two undetected neutrinos require a new reconstruction scheme for the four-momenta of the final state particles, the small event sample demands the modeling of additional jets in the signal likelihood, and a new likelihood is designed to account for the main source of background containing tauonic Z decay. The Matrix Element method is validated on Monte Carlo simulated events at the generator level. For the measurement, calibration curves are derived from events that are run through the full D0 detector simulation. The analysis makes use of the Run II data set recorded between April 2002 and May 2008 corresponding to an integrated luminosity of 2.8 fb−1. A total of 107 t{bar t} candidate events with one electron and one muon in the final state are selected. Applying the Matrix Element method to this data set, the top quark mass is measured to be m{sub top}{sup Run IIa} = 170.6 ± 6.1(stat.){sub -1.5}{sup +2.1}(syst.)GeV; m{sub top}{sup Run IIb} = 174.1 ± 4.4(stat.){sub -1.8}{sup +2.5}(syst.)GeV; m{sub top}{sup comb} = 172.9 ± 3.6(stat.) ± 2.3(syst.)GeV. Systematic uncertainties are discussed, and the results are interpreted within the Standard Model of particle physics. As the main systematic uncertainty on the top quark mass comes from the knowledge of the absolute jet energy scale, studies for a simultaneous measurement of the top quark mass and the b jet energy scale are presented. The prospects that such a simultaneous determination offer for future measurements of the top quark mass are outlined.
Download or read book Top Quark Mass in Events with Two Charged Leptons at the D0 Experiment written by and published by . This book was released on 2010 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the most massive observed fundamental subatomic particle, and at the Tevatron accelerator is produced mostly in top-antitop (t{bar t}) quark pairs from the collisions of protons and anti-protons. Each top quark decays into a bottom quark and a W boson. The W boson can then decay into a pair of quarks, or into a charged lepton and a neutrino. The various decays can be broken up into three different channels based on the number of leptons from the decay of the W bosons: all-jets (with no leptons), lepton+jets (with one lepton), and dilepton (with two leptons). This dissertation will present a measurement of the top quark mass in the dilepton channel. The dilepton channel is characterized by two leptons, two neutrinos and two b-quarks. The neutrinos are not directly observed, but their absence is felt as missing transverse momentum (p{sub T}) in the detector. The combination of two leptons and large p{sub T} produces an easily isolated signal, giving the dilepton channel a high signal over background ratio. Having two neutrinos means that we cannot know what the transverse momenta of either neutrino is. This means that even if we knew the momenta of the leptons and b-quarks perfectly, we would be unable to reconstruct the mass of the top quark. This measurement gets around this problem by scanning over all possible values of the top mass, finding all consistent t{bar t} combinations, assigning a kinematic weight to each, and then adding the weights for each combination at a given possible top mass. The lepton momenta, jet momenta, and p{sub T} are only known to within some finite precision, so for a given top mass, I also vary each of these momenta within their resolutions and add the weights for a given possible top mass. After scanning over possible top masses, I choose the top mass with the largest sum of weights m{sub t}{sup max} as an observable for the event. I then perform a template based likelihood fit of m{sub t} using m{sub t}{sup max}. I analyze 322 candidate events collected by the D0 detector, and obtain a top quark mass of: m{sub t} = 174.8 ± 3.1 GeV.
Download or read book Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method written by Alexander Grohsjean and published by . This book was released on 2010 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark, discovered in 1995 at the Fermilab Tevatron Collider, is the heaviest known elementary particle. The precise knowledge of its mass yields important constraints on the mass of the as-yet-undiscovered Higgs boson and allows one to probe for physics beyond the Standard Model. With an excellent adaptation of a novel measurement technique, described and applied here for the first time, the sensitivity to the top quark mass in the dilepton final state at the D0 experiment could be improved by more than 30%. Moreover, an extension to the method is presented which allows future measurements to significantly reduce the main limiting systematic uncertainty.
Download or read book Measurement of the Top Quark Mass Using the Dilepton and Lepton Track Event Samples of the CDF Experiment on Tevatron In Russian written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Top Quark Mass in Events with Two Charged Leptons at the D0 Experiment written by Daniel Boline and published by . This book was released on 2010 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The top quark is the most massive observed fundamental subatomic particle, and at the Tevatron accelerator is produced mostly in top-antitop ( tt ) quark pairs from the collisions of protons and anti-protons. Each top quark decays into a bottom quark and a W boson. The W boson can then decay into a pair of quarks, or into a charged lepton and a neutrino. The various decays can be broken up into three different channels based on the number of leptons from the decay of the W bosons: all-jets (with no leptons), lepton+jets (with one lepton), and dilepton (with two leptons). This dissertation will present a measurement of the top quark mass in the dilepton channel. The dilepton channel is characterized by two leptons, two neutrinos and two b-quarks. The neutrinos are not directly observed, but their absence is felt as missing transverse momentum ([Special characters omitted.] ) in the detector. The combination of two leptons and large [Special characters omitted.] produces an easily isolated signal, giving the dilepton channel a high signal over background ratio. Having two neutrinos means that we cannot know what the transverse momenta of either neutrino is. This means that even if we knew the momenta of the leptons and b-quarks perfectly, we would be unable to reconstruct the mass of the top quark. This measurement gets around this problem by scanning over all possible values of the top mass, finding all consistent tt combinations, assigning a kinematic weight to each, and then adding the weights for each combination at a given possible top mass. The lepton momenta, jet momenta, and [Special characters omitted.] are only known to within some finite precision, so for a given top mass, I also vary each of these momenta within their resolutions and add the weights for a given possible top mass. After scanning over possible top masses, I choose the top mass with the largest sum of weights [Special characters omitted.] as an observable for the event. I then perform a template based likelihood fit of m t using [Special characters omitted.] . I analyze 322 candidate events collected by the DØ detector, and obtain a top quark mass of: [Special characters omitted.]
Download or read book Top Quark Mass Measurement from Dilepton Events at CDF II written by and published by . This book was released on 2005 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the Top Quark Mass by Application of the Dalitz Goldstein Method to Dilepton Events written by Kristo Michael Karr and published by . This book was released on 1999 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents a measurement of the top quark mass by application of the Dalitz-Goldstein method to dilepton tt ̄ events. The events were produced by the Tevatron Collider at Fermi National Accelerator Laboratory (Fermilab) via pp ̄ collisions with s = 1.8 TeV. The dilepton event sample was extracted from 109 pb --1 of data collected by the Collider Detector at Fermilab (CDF) from August 1992 to July 1995. The sample contains a total of 9 candidate events, 2.4 of which are expected from background. Included in the dilepton final state are two neutrinos, which elude detection. This analysis constrains the problem by assuming an initial value for the top quark mass and solving for the neutrino momenta via a geometrical construction developed by D. H. Dalitz and G. Goldstein. The top quark mass is sampled over a wide range of possible values and the most likely mass consistent with the data is chosen via a likelihood function. An important distinguishing feature of this mass fitting technique is its lack of dependence on missing transverse energy, a kinematic variable that is poorly measured by experiment. This analysis determines the top quark mass to be Mtop = 157.1 +/- 10.9(stat.) +/- 4.33.7 (syst.) GeV/c2.
