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Precise Measurement Of The Top Quark Mass In Dilepton Decays Using Optimized Neutrino Weighting
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Book Synopsis Precise Measurement of the Top Quark Mass in Dilepton Decays Using Optimized Neutrino Weighting by :
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.
Book Synopsis Measurement of the Top Quark Mass in Dilepton Final States with the Neutrino Weighting Method by :
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.
Book Synopsis Measurement of the Mass of the Top Quark in Dilepton Final States with the D0 Detector by : Oleg Brandt
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.
Book Synopsis A Precise Measurement of the Top Quark Mass in Dilepton Final States Using 9.7 Fb$^{-1}$ of D{\O} Run II Data by :
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 .
Book Synopsis Measurement of the Top Quark Mass Using Dilepton Events and a Neutrino Weighting Algorithm with the D0 Experiment at the Tevatron (Run II). by :
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.
Book Synopsis Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method by : Alexander Grohsjean
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 Springer Science & Business Media. This book was released on 2010-10-01 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main pacemakers of scienti?c research are curiosity, ingenuity, and a pinch of persistence. Equipped with these characteristics a young researcher will be s- cessful in pushing scienti?c discoveries. And there is still a lot to discover and to understand. In the course of understanding the origin and structure of matter it is now known that all matter is made up of six types of quarks. Each of these carry a different mass. But neither are the particular mass values understood nor is it known why elementary particles carry mass at all. One could perhaps accept some small generic mass value for every quark, but nature has decided differently. Two quarks are extremely light, three more have a somewhat typical mass value, but one quark is extremely massive. It is the top quark, the heaviest quark and even the heaviest elementary particle that we know, carrying a mass as large as the mass of three iron nuclei. Even though there exists no explanation of why different particle types carry certain masses, the internal consistency of the currently best theory—the standard model of particle physics—yields a relation between the masses of the top quark, the so-called W boson, and the yet unobserved Higgs particle. Therefore, when one assumes validity of the model, it is even possible to take precise measurements of the top quark mass to predict the mass of the Higgs (and potentially other yet unobserved) particles.
Book Synopsis Measurement of M_{top} Via Neutrino Weighting in the Dilepton Decay Channels at by : Jeffrey W. Temple
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.
Book Synopsis A Precision Measurement of the Top Quark Mass by : Kevin Matthew Black
Download or read book A Precision Measurement of the Top Quark Mass written by Kevin Matthew Black and published by . This book was released on 2005 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the measurement of the top quark mass using events recorded during a {approx} 230 pb{sup -1} exposure of the D0 detector to proton-anti-proton (p{bar p}) collisions at a center of mass energy of 1.96 TeV. The Standard Model of particle physics predicts that the top quark will decay into a bottom quark and a W boson close to 100% of the time. The bottom quark will hadronize (bind with another quark) and produce a jet of hadronic particles. The W bosons can decay either into a charged lepton and a neutrino or a pair of quarks. this dissertation focuses on the top quark (t{bar t}) events in which one W decays hadronically and the other decays leptonically. Two methods of identifying t{bar t} events from the large number of events produced are used. The first is based on the unique topology of the final state particles of a heavy particle. By using the topological information of the event, the t{bar t} events can be efficiently extracted from the background. The second method relies on the identification of the remnants of the long lived bottom quarks that are expected to be produced in the decay of almost every top quark. Because the largest background processes do not contain bottom quarks, this is an extremely efficient way to select the events retaining about 60% of the t{bar t} events and removing almost 90% of the background. A kinematic fit to the top quark mass is performed on the t{bar t} candidate events using the final state particles that are seen in the detector. A likelihood technique is then used to extract the most likely value of the top quark mass, m{sub t}, and signal fraction. The result for the topological selection is m{sub t} = 169.9 {+-} 5.8(statistical){sub -7.8}{sup +8.0}(systematic) GeV while the results on the sample selected from identification of a b quark in the event is m{sub t} = 170.6 {+-} 4.2(statistical){sub -6.8}{sup +6.3}(systematic) GeV.
Download or read book Top Quark Mass Measurement written by and published by . This book was released on 2008 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the heaviest elementary particle. Its mass is one of the fundamental parameters of the standard model of particle physics, and an important input to precision electroweak tests. This thesis describes three measurements of the top-quark mass in the dilepton decay channel. The dilepton events have two neutrinos in the final state; neutrinos are weakly interacting particles that cannot be detected with a multipurpose experiment. Therefore, the signal of dilepton events consists of a large amount of missing energy and momentum carried off by the neutrinos. The top-quark mass is reconstructed for each event by assuming an additional constraint from a top mass independent distribution. Template distributions are constructed from simulated samples of signal and background events, and parametrized to form continuous probability density functions. The final top-quark mass is derived using a likelihood fit to compare the reconstructed top mass distribution from data to the parametrized templates. One of the analyses uses a novel technique to add top mass information from the observed number of events by including a cross-section-constraint in the likelihood function. All measurements use data samples collected by the CDF II detector.
Book Synopsis Measurement of the Top Quark Mass Using Dilepton Events and a Neutrino Weighting Algorithm with the DØ Experiment at the Tevatron (Run II) by : Jörg Meyer
Download or read book Measurement of the Top Quark Mass Using Dilepton Events and a Neutrino Weighting Algorithm with the DØ 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:
Book Synopsis Measurement of the Top Quark Mass in the Dilepton Channel Using the Neutrino Weighting Algorithm at CDF II. by : Simon Sabik
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.
Book Synopsis Precision Measurement of the Top Quark Mass from Dilepton Events at CDF II. by :
Download or read book Precision Measurement of the Top Quark Mass from Dilepton Events at CDF II. written by and published by . This book was released on 2006 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Precision Measurement of Top Quark Mass in Dilepton Channel by : Bodhitha Jayatilaka
Download or read book Precision Measurement of Top Quark Mass in Dilepton Channel written by Bodhitha Jayatilaka and published by . This book was released on 2006 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present recent measurements of the top quark mass using events collected at the CDF and D0 detectors from p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron. These analyses are performed using events consistent with the decay channel t{bar t} {yields} {bar b}{ell}{sup -}{bar v}{sub {ell}}b{ell}' + v'{sub {ell}}, or the dilepton channel. 230-360 pb{sup -1} of data are used.
Book Synopsis Measurement of the Top Quark Mass Simultaneously in Dilepton and Lepton + Jets Decay Channels by :
Download or read book Measurement of the Top Quark Mass Simultaneously in Dilepton and Lepton + Jets Decay Channels written by and published by . This book was released on 2008 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present the first measurement of the top quark mass using simultaneously data from two decay channels. They use a data sample of (square root)s = 1.96 TeV collisions with integrated luminosity of 1.9 fb−1 collected by the CDF II detector. They select dilepton and lepton + jets channel decays of t{bar t} pairs and reconstruct two observables in each topology. They use non-parametric techniques to derive probability density functions from simulated signal and background samples. The observables are the reconstructed top quark mass and the scalar sum of transverse energy of the event in the dilepton topology and the reconstructed top quark mass and the invariant mass of jets from the W boson decay in lepton + jets channel. They perform a simultaneous fit for the top quark mass and the jet energy scale which is constrained in situ by the hadronic W boson resonance from the lepton + jets channel. Using 144 dilepton candidate events and 332 lepton + jets candidate events they measure: M{sub top} = 171.9 ± 1.7 (stat. + JES) ± 1.1 (other sys.) GeV/c2 = 171.9 ± 2.0 GeV/c2. The measurement features a robust treatment of the systematic uncertainties, correlated between the two channels and develops techniques for a future top quark mass measurement simultaneously in all decay channels. Measurements of the W boson mass and the top quark mass provide a constraint on the mass of the yet unobserved Higgs boson. The Higgs boson mass implied by measurement presented here is higher than Higgs boson mass implied by previously published, most precise CDF measurements of the top quark mass in lepton + jets and dilepton channels separately.
Book Synopsis Precision Measurements of the Top Quark Mass and Width with the D0 Detector by :
Download or read book Precision Measurements of the Top Quark Mass and Width with the D0 Detector written by and published by . This book was released on 2010 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the discovery of the top quark in 1995 at the Fermliab Tevatron Collider, top quark properties have been measured with ever higher precision. In this article, recent measurements of the top quark mass and its width using up to 3.6 fb−1 of D0 data are summarized. Different techniques and final states have been examined and no deviations within these measurements have been observed. In addition to the direct measurements, a measurement of the top quark mass from its production cross section and a measurement of the top-antitop quark mass difference are discussed. With a mass of 173.3 ± 1.1 GeV, the top quark is the heaviest of all known fundamental particles. Due to the high mass, its Yukawa coupling is close to unity suggesting that it may play a special role in electroweak symmetry breaking. Precise measurements of both, the W boson and the top quark mass, constrain the mass of the yet unobserved Higgs boson and allow to restrict certain extensions of the Standard Model. At the Tevatron collider with a center-of-mass energy of 1.96 TeV, 85% of the top quark pairs are produced in quark-antiquark annihilation; 15% originate from gluon fusion. Top quarks are predicted to decay almost exclusively to a W boson and a bottom quark. According to the number of hadronic W decays, top events are classified into all-jets, lepton+jets and dilepton events. The lepton+jets channel is characterized by four jets, one isolated, energetic charged lepton and missing transverse energy. With 30%, the branching fraction of the lepton+jets channel is about seven times larger than the one of the dilepton channel whereas the signal to background ratio is about three times smaller. The main background in this final state comes from W +jets events. Instrumental background arises from events in which a jet is misidentified as an electron and events with heavy hadrons that decay into leptons which pass the isolation requirements. The topology of the dilepton channel is described by two jets, two isolated, energetic charged leptons and significant missing transverse energy from the undetected neutrinos. The main background are Z + jets and diboson events (WW/WZ/ZZ+jets) as well as instrumental background as characterized above. At the D0 experiment, different techniques are used to measure the top quark mass. They are summarized in the following sections together with the first measurement of the top anti-top quark mass difference and the first precise determination of the top quark width.
Book Synopsis Top Quark Mass in Events with Two Charged Leptons at the D0 Experiment by :
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.
Book Synopsis Top Quark Mass in Events with Two Charged Leptons at the D0 Experiment by : Daniel Boline
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.]
