Measurement Of The W Boson Helicity In Events With A Single Reconstructed Top Quark In Pp Collisions At Sqrt S
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Measurement Of The W Boson Helicity In Events With A Single Reconstructed Top Quark In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2015
Measurement Of The W Boson Helicity In Events With A Single Reconstructed Top Quark In Pp Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
A measurement of the W boson helicity is presented, where the W boson originates from the decay of a top quark produced in pp collisions. The event selection, optimized for reconstructing a single top quark in the final state, requires exactly one isolated lepton (muon or electron) and exactly two jets, one of which is likely to originate from the hadronization of a bottom quark. The analysis is performed using data recorded at a center-of-mass energy of 8 TeV with the CMS detector at the CERN LHC in 2012. The data sample corresponds to an integrated luminosity of 19.7 fb$^{-1}$. The measured helicity fractions are F$_{L}$ = 0.298 " 0.028 (stat) " 0.032(syst), F$_{0}$ = 0.720 " 0.039 (stat) " 0.037(syst), and F$_{R}$ = -0.018 " 0.019 (stat) " 0.011(syst). These results are used to set limits on the real part of the tWb anomalous couplings, g$_{L}$ and g$_{R}$.
Measurement Of The W Boson Helicity Fractions In The Decays Of Top Quark Pairs To Lepton Jets Final States Produced In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2016
Measurement Of The W Boson Helicity Fractions In The Decays Of Top Quark Pairs To Lepton Jets Final States Produced In Pp Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
The W boson helicity fractions from top quark decays in t-tbar events are measured using data from proton-proton collisions at a centre-of-mass energy of 8 TeV. The data were collected in 2012 with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 inverse-femtobarns. Events are reconstructed with either one muon or one electron, along with four jets in the final state, with two of the jets being identified as originating from b quarks. The measured helicity fractions from both channels are combined, yielding F[0] = 0.681 +/- 0.012 (stat) +/- 0.023 (syst), F[L] = 0.323 +/- 0.008 (stat) +/- 0.014 (syst), and F[R] = -0.004 +/- 0.005 (stat) +/- 0.014 (syst) for the longitudinal, left-, and right-handed components of the helicity, respectively. These measurements of the W boson helicity fractions are the most accurate to date and they agree with the predictions from the standard model.
Index To Theses With Abstracts Accepted For Higher Degrees By The Universities Of Great Britain And Ireland And The Council For National Academic Awards
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Author :
language : en
Publisher:
Release Date : 2007
Index To Theses With Abstracts Accepted For Higher Degrees By The Universities Of Great Britain And Ireland And The Council For National Academic Awards written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Dissertations, Academic categories.
Measurement Of The W Boson Helicity In Top Quark Decays From T Bar T Production In Lepton Jets Events In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2013
Measurement Of The W Boson Helicity In Top Quark Decays From T Bar T Production In Lepton Jets Events In Pp Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Measurement Of The Top Quark Mass Using Single Top Quark Events In Proton Proton Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2017
Measurement Of The Top Quark Mass Using Single Top Quark Events In Proton Proton Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
A measurement of the top quark mass is reported in events containing a single top quark produced via the electroweak t channel. The analysis is performed using data from proton-proton collisions collected with the CMS detector at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The top quark is reconstructed from its decay to a W boson and a b quark, with the W boson decaying leptonically to a muon and a neutrino. The specific topology and kinematic properties of single top quark events in the t channel are used to enhance the purity of the sample, suppressing the contribution from top quark pair production. A fit to the invariant mass distribution of reconstructed top quark candidates yields a value of the top quark mass of 172.95 +/- 0.77 (stat) +0.97/-0.93 (syst) GeV. This result is in agreement with the current world average, and represents the first measurement of the top quark mass in event topologies not dominated by top quark pair production.
Measurement Of The W Boson Helicity In Top Antitop Quark Events With The Cdf Ii Experiment
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Author : Thorsten Chwalek
language : en
Publisher:
Release Date : 2006
Measurement Of The W Boson Helicity In Top Antitop Quark Events With The Cdf Ii Experiment written by Thorsten Chwalek and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
In 1995 the top quark was discovered at the Tevatron proton-antiproton collider at Fermilab by the CDF and D0 collaborations [1, 2]. It is the most massive known elementary particle and its mass is currently measured with a precision of about 1.3% [3, 4]. However, the measurements of several other top quark properties are still statistically limited, so the question remains whether the Standard Model of elementary particle physics successfully predicts these properties. This thesis addresses one interesting aspect of top quark decay, the helicity of the produced W boson. Until the start of the Large Hadron Collider (LHC) at CERN, the Tevatron with a center-of-mass energy of {radical}s = 1.96 TeV is the only collider, where top quarks can be produced. In the Standard Model the top quark decays predominantly into a W boson and a b quark, with a branching ratio close to 100%. The V-A structure of the weak interaction of the Standard Model predicts that the W{sup +} bosons from the top quark decay t {yields} W{sup +}b are dominantly either longitudinally polarized or left handed, while right handed W bosons are heavily suppressed and even forbidden in the limit of a massless b quark. Under the assumption of a massless b quark, for a top quark mass of 173 GeV/c{sup 2} the Standard Model predicts the fraction F0 of longitudinally polarized W bosons to be 0.7 and 0.3 for the fraction F{_} of left handed W bosons, while the fraction F{sub +} of right handed W bosons is predicted to be zero. Since next-to-leading order corrections change these fractions only slightly, a significant deviation from the predicted value for F{sub 0} or a nonzero value for F{sub +} could indicate new physics. Left-right symmetric models [5], for example, lead to a significant right handed fraction of W bosons in top decays. Such a right handed component (V+A coupling) would lead to a smaller left handed fraction, while F{sub 0} would remain unchanged. Since the decay rate to longitudinal W bosons depends on the Yukawa coupling of the top quarks, the measurement of F{sub 0} is sensitive to the mechanism of electroweak symmetry breaking. Alternative models can lead to an altered F{sub 0} fraction. In this analysis the W helicity fractions are measured in a selected sample rich in t{bar B} events where one lepton, at least four jets, and missing transverse energy are required. All kinematic quantities describing the t{bar t} decay are determined. As a sensitive observable, we use the cosine of the decay angle {theta}*, which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W boson momentum in the top quark rest frame. The data used in this analysis were taken with the Collider Detector at Fermilab (CDF II) in the years 2002-2006 and correspond to an integrated luminosity of about 955 pb{sup -1}. Previous CDF measurements of the W boson helicity fractions in top quark decays used either the square of the invariant mass of the charged lepton and the b quark jet, M{sub {ell}b}{sup 2}, or the lepton p{sub T} distribution as a discriminant. The D0 collaboration used a matrix-element method to extract a value of F{sub 0}; in a second analysis the reconstructed distribution of cos {theta}* was utilized to measure F{sub +}. CDF gives the latest value of F{sub 0} = 0.74{sub -0.34}{sup +0.22}, while D measured F{sub 0} = 0.56 {+-} 0.31. The CDF collaboration also gives the current upper limit of F{sub +}
Measurement Of The W Boson Helicity In Top Quark Decays Using 5 4 Fb Boldsymbol 1 Of Boldsymbol P Bar P Collision Data
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Author :
language : en
Publisher:
Release Date : 2010
Measurement Of The W Boson Helicity In Top Quark Decays Using 5 4 Fb Boldsymbol 1 Of Boldsymbol P Bar P Collision Data written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
We present a measurement of the helicity of the W boson produced in top quark decays using t{bar t} decays in the l+jets and dilepton final states selected from a sample of 5.4 fb−1 of collisions recorded using the D0 detector at the Fermilab Tevatron p{bar p} collider. We measure the fractions of longitudinal and right-handed W bosons to be f0 = 0.669 ± 0.102 [±0.078 (stat.) ± 0.065 (syst.)] and f+ = 0.023 ± 0.053 [±0.041 (stat.)±0.034 (syst.)], respectively. This result is consistent at the 98% level with the standard model. A measurement with f0 fixed to the value from the standard model yields f+ = 0.010 ± 0.037 [±0.022 (stat.) ± 0.030 (syst.)].
Measurement Of The Mass Of The Top Quark In Decays With A J Psi Meson In Pp Collisions At 8 Tev
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Author :
language : en
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Release Date : 2016
Measurement Of The Mass Of The Top Quark In Decays With A J Psi Meson In Pp Collisions At 8 Tev written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
A first measurement is presented of the top quark mass using the decay channel $ \mathrm{ t } \to (\mathrm{ W } \to\ell\nu)$, $(\mathrm{ b } \to \mathrm{ J } / \psi + \mathrm{X} \to \mu \mu + \mathrm{X}) $, in events selected in proton-proton collisions and recorded with the CMS detector at the LHC at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 fb$^{-1}$, with 666 $\mathrm{ t \bar{t} }$ and single top quark candidate events containing a reconstructed $\mathrm{ J } / \psi$ candidate decaying into an oppositely-charged muon pair. The mass of the ($\mathrm{ J } / \psi+\ell$) system, where $\ell$ is an electron or a muon from W boson decay, is used to extract a top quark mass of 173.5 $\pm$ 3.0 (stat) $\pm$ 0.9 (syst) GeV.
Measurement Of The Top Quark Mass In All Jets T Bar T Events In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2013
Measurement Of The Top Quark Mass In All Jets T Bar T Events In Pp Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
The mass of the top quark is measured using a sample of $t\bar{t}$ candidate events with at least six jets in the final state. The sample is selected from data collected with the CMS detector in pp collisions at $\sqrt{s}$ = 7 TeV in 2011 and corresponds to an integrated luminosity of 3.54 inverse femtobarns. The mass is reconstructed for each event employing a kinematic fit of the jets to a $t\bar{t}$ hypothesis. The top-quark mass is measured to be 173.49 $\pm$ 0.69 (stat.) $\pm$ 1.21 (syst.) GeV. A combination with previously published measurements in other decay modes by CMS yields a mass of 173.54 $\pm$ 0.33 (stat.) $\pm$ 0.96 (syst.) GeV.
Observation Of The Associated Production Of A Single Top Quark And A W Boson In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2014
Observation Of The Associated Production Of A Single Top Quark And A W Boson In Pp Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.