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Author :
Publisher :
ISBN 13 :
Total Pages : 21 pages
Book Rating : 4.:/5 (873 download)
Download or read book Top Quark Mass Measurement from Dilepton Events at CDF II with the Matrix-element Method written by and published by . This book was released on 2006 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 153 pages
Book Rating : 4.:/5 (727 download)
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.
Author : Adam Paul Gibson
Publisher :
ISBN 13 :
Total Pages : 400 pages
Book Rating : 4.:/5 (35 download)
Download or read book A Measurement of the Top Quark Mass with a Matrix Element Method written by Adam Paul Gibson and published by . This book was released on 2006 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 7 pages
Book Rating : 4.:/5 (871 download)
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:
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ISBN 13 :
Total Pages : 7 pages
Book Rating : 4.:/5 (873 download)
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:
Author : Alexander Grohsjean
Publisher :
ISBN 13 : 9783642140716
Total Pages : 148 pages
Book Rating : 4.1/5 (47 download)
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.
Author : Alexander Grohsjean
Publisher : Springer Science & Business Media
ISBN 13 : 364214070X
Total Pages : 155 pages
Book Rating : 4.6/5 (421 download)
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.
Author : John Freeman
Publisher :
ISBN 13 :
Total Pages : 384 pages
Book Rating : 4.:/5 (34 download)
Download or read book A Measurement of the Top Quark Mass in 1.96 TeV Proton-antiproton Collisions Using a Novel Matrix Element Method written by John Freeman and published by . This book was released on 2007 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Brian Mohr
Publisher :
ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (316 download)
Download or read book Measurement of the Top Quark Mass with a Matrix Element Method in the Lepton Plus Jets Channel at CDF. written by Brian Mohr and published by . This book was released on 2006 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present a measurement of the mass of the top quark from p{bar p} collisions at 1.96 TeV observed with the Collider Detector at Fermilab (CDF) at the Fermilab Tevatron Run II. The events have the decay signature of p{bar p} {yields} t{bar t} in the lepton plus jets channel in which at least one jet is identified as coming from a secondary vertex and therefore a b-hadron. The largest systematic uncertainty, the jet energy scale (JES), is convoluted with the statistical error using an in-situ measurement of the hadronic W boson mass. They calculate a likelihood for each event using leading-order t{bar t} and W+jets cross-sections and parameterized parton showering. The final measured top quark mass and JES systematic is extracted from a joint likelihood of the product of individual event likelihoods. From 118 events observed in 680 pb{sup -1} of data, they measure a top quark mass of 174.09 {+-} 2.54 (stat+JES) {+-} 1.35(syst) GeV/c{sup 2}.
Author : Bodhitha Anjalike Jayatilaka
Publisher :
ISBN 13 :
Total Pages : 272 pages
Book Rating : 4.3/5 (91 download)
Download or read book A Measurement of the Top Quark Mass in the Dilepton Decay Channel at CDF II. written by Bodhitha Anjalike Jayatilaka and published by . This book was released on 2006 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 169 pages
Book Rating : 4.:/5 (873 download)
Download or read book A Top Quark Mass Measurement Using a Matrix Element Method written by and published by . This book was released on 2010 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the mass of the top quark is presented, using top-antitop pair (t{bar t}) candidate events for the lepton+jets decay channel. The measurement makes use of Tevatron p{bar p} collision data at centre-of-mass energy √s = 1.96 TeV, collected at the CDF detector. The top quark mass is measured by employing an unbinned maximum likelihood method where the event probability density functions are calculated using signal (t{bar t}) and background (W+jets) matrix elements, as well as a set of parameterised jet-to-parton mapping functions. The likelihood function is maximised with respect to the top quark mass, the fraction of signal events, and a correction to the jet energy scale (JES) of the calorimeter jets. The simultaneous measurement of the JES correction ([Delta]{sub JES}) provides an in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using 578 lepton+jets candidate events corresponding to 3.2 fb−1 of integrated luminosity, the top quark mass is measured to be m{sub t} = 172.4 ± 1.4 (stat+[Delta]{sub JES}) ± 1.3 (syst) GeV=c2, one of the most precise single measurements to date.
Author : Philipp Schieferdecker
Publisher :
ISBN 13 :
Total Pages : 182 pages
Book Rating : 4.:/5 (316 download)
Download or read book Measurement of the Top Quark Mass at D0 Run II with the Matrix Element Method in the Lepton+Jets Final State written by Philipp Schieferdecker and published by . This book was released on 2005 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mass of the top quark is a fundamental parameter of the Standard Model. Its precise knowledge yields valuable insights into unresolved phenomena in and beyond the Standard Model. A measurement of the top quark mass with the matrix element method in the lepton+jets final state in D0 Run II is presented. Events are selected requiring an isolated energetic charged lepton (electron or muon), significant missing transverse energy, and exactly four calorimeter jets. For each event, the probabilities to originate from the signal and background processes are calculated based on the measured kinematics, the object resolutions and the respective matrix elements. The jet energy scale is known to be the dominant source of systematic uncertainty. The reference scale for the mass measurement is derived from Monte Carlo events. The matrix element likelihood is defined as a function of both, m{sub top} and jet energy scale JES, where the latter represents a scale factor with respect to the reference scale. The top mass is obtained from a two-dimensional correlated fit, and the likelihood yields both the statistical and jet energy scale uncertainty. Using a dataset of 320 pb{sup -1} of D0 Run II data, the mass of the top quark is measured to be: m{sub top}{sup {ell}+jets} = 169.5 {+-} 4.4(stat. + JES){sub -1.6}{sup +1.7}(syst.) GeV; m{sub top}{sup e+jets} = 168.8 {+-} 6.0(stat. + JES){sub -1.9}{sup +1.9}(syst.) GeV; m{sub top}{sup {mu}+jets} = 172.3 {+-} 9.6(stat.+JES){sub -3.3}{sup +3.4}(syst.) GeV. The jet energy scale measurement in the {ell}+jets sample yields JES = 1.034 {+-} 0.034, suggesting good consistency of the data with the simulation. The measurement forecasts significant improvements to the total top mass uncertainty during Run II before the startup of the LHC, as the data sample will grow by a factor of ten and D0's tracking capabilities will be employed in jet energy reconstruction and flavor identification.
Author :
Publisher :
ISBN 13 :
Total Pages : 189 pages
Book Rating : 4.:/5 (727 download)
Download or read book A Measurement of the Top Quark Mass in 1.96 TeV Proton-antiproton Collisions Using a Novel Matrix Element Method written by and published by . This book was released on 2007 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the top quark mass in t{bar t} --> l + jets candidate events, obtained from p{bar p} collisions at (square root)s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector, is presented. The measurement approach is that of a matrix element method. For each candidate event, a two dimensional likelihood is calculated in the top pole mass and a constant scale factor, 'JES', where JES multiplies the input particle jet momenta and is designed to account for the systematic uncertainty of the jet momentum reconstruction. As with all matrix elements techniques, the method involves an integration using the Standard Model matrix element for tt production and decay. however, the technique presented is unique in that the matrix element is modified to compensate for kinematic assumptions which are made to reduce computation time. Background events are dealt with through use of an event observable which distinguishes signal from background, as well as through a cut on the value of an event's maximum likelihood. Results are based on a 955 pb−1 data sample, using events with a high-p{sub T} lepton and exactly four high-energy jets, at least one of which is tagged as coming from a b quark; 149 events pass all the selection requirements. They find M{sub meas} = 169.8 ± 2.3(stat.) ± 1.4(syst.) GeV/c2.
Author :
Publisher :
ISBN 13 :
Total Pages : 46 pages
Book Rating : 4.:/5 (727 download)
Download or read book Top Quark Mass Measurement in the Lepton Plus Jets Channel Using a Modified Matrix Element Method written by and published by . This book was released on 2008 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors report a measurement of the top quark mass, m{sub t}, obtained from p{bar p} collisions at (square root)s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector. They analyze a sample corresponding to an integrated luminosity of 1.9 rfb−1. They select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. They calculate a signal likelihood using a matrix element integration method, where the matrix element is modified by using effective propagators to take into account assumptions on event kinematics. The event likelihood is a function of m{sub t} and a parameter JES that determines in situ the calibration of the jet energies. They use a neural network discriminant to distinguish signal from background events. They also apply a cut on the peak value of each event likelihood curve to reduce the contribution of background and badly reconstructed events. Using the 318 events that pass all selection criteria, they find m{sub t} = 172.7 ± 1.8 (stat. + JES) ± 1.2(syst.) GeV/c2.
Author :
Publisher :
ISBN 13 :
Total Pages : 9 pages
Book Rating : 4.:/5 (873 download)
Download or read book Measurement of the Top-quark Mass in the Lepton+jets Channel Using a Matrix Element Technique with the CDF II Detector written by and published by . This book was released on 2011 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the top-quark mass is presented using Tevatron data from proton-antiproton collisions at center-of-mass energy √ = 1.96 TeV collected with the CDF II detector. Events are selected from a sample of candidates for production of t{bar t} pairs that decay into the lepton+jets channel. The top-quark mass is measured with an unbinned maximum likelihood method where the event probability density functions are calculated using signal and background matrix elements, as well as a set of parameterized jet-to-parton transfer functions. The likelihood function is maximized with respect to the top-quark mass, the signal fraction in the sample, and a correction to the jet energy scale (JES) calibration of the calorimeter jets. The simultaneous measurement of the JES correction ([Delta]{sub JES}) amounts to an additional in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using the data sample of 578 lepton+jets candidate events, corresponding to 3.2 fb−1 of integrated luminosity, the top-quark mass is measured to be m{sub t} = 172.4 ± 1.4 (stat + [Delta]{sub JES}) ± 1.3 (syst) GeV/c2.
Author :
Publisher :
ISBN 13 :
Total Pages : 194 pages
Book Rating : 4.:/5 (727 download)
Download or read book Measurement of the Top Quark Mass with the Matrix Element Method in the Semileptonic Decay Channel at written by and published by . This book was released on 2008 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
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ISBN 13 :
Total Pages : 43 pages
Book Rating : 4.:/5 (727 download)
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.
