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Combination Of Cdf And D0 Measurements Of The W Boson Helicity In Top Quark Decays
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Book Synopsis Combination of CDF and D0 Measurements of the $W$ Boson Helicity in Top Quark Decays by :
Download or read book Combination of CDF and D0 Measurements of the $W$ Boson Helicity in Top Quark Decays written by and published by . This book was released on 2012 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of 2.7-5.4 fb−1 of p{bar p} collisions collected during Run II of the Fermilab Tevatron Collider. Combining measurements that simultaneously determine the fractions of W bosons with longitudinal (f0) and right-handed (f+) helicities, we find f0 = 0.722 ± 0.081 [± 0.062 (stat.) ± 0.052 (syst.)] and f+ = -0.033 ± 0.046 [± 0.034 (stat.) ± 0.031 (syst.)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f0 = 0.682 ± 0.057 [± 0.035 (stat.) ± 0.046 (syst.)] and f+ =?0.015 ± 0.035 [± 0.018 (stat.) ± 0.030 (syst.)]. The results are consistent with standard model expectations.
Book Synopsis Measurement of the W Boson Helicity in Top-antitop Quark Events with the CDF II Experiment by : Thorsten Chwalek
Download or read book Measurement of the W Boson Helicity in Top-antitop Quark Events with the CDF II Experiment written by Thorsten Chwalek and published by . This book was released on 2006 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 +}
Book Synopsis Measurement of the W Boson Helicity in Top Quark Decay at by :
Download or read book Measurement of the W Boson Helicity in Top Quark Decay at written by and published by . This book was released on 2006 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present a measurement of the fraction f+ of right-handed W bosons produced in top quark decays, based on a candidate sample of t{bar t} events in the l+jets and dilepton decay channels corresponding to an integrated luminosity of 370 pb−1 collected by the D0 detector at the Fermilab Tevatron p{bar p} Collider at √s = 1.96 TeV. They reconstruct the decay angle [theta]* for each lepton. By comparing the cos[theta]* distribution from the data with those for the expected background and signal for various values of f+, they find f+ = 0.056 ± 0.080(stat) ± 0.057(syst). (f+
Book Synopsis Model-independent Measurement of the W Boson Helicity in Top Quark Decays at by :
Download or read book Model-independent Measurement of the W Boson Helicity in Top Quark Decays at written by and published by . This book was released on 2007 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the first model-independent measurement of the helicity of W bosons produced in top quark decays, based on a 1 fb−1 sample of candidate t{bar t} events in the dilepton and lepton plus jets channels collected by the D0 detector at the Fermilab Tevatron p{bar p} Collider. We reconstruct the angle [theta]* between the momenta of the down-type fermion and the top quark in the W boson rest frame for each top quark decay. A fit of the resulting cos [theta]* distribution finds that the fraction of longitudinal W bosons f0 = 0.390 ± 0.177 (stat.) ± 0.104 (syst.) and the fraction of right-handed W bosons f+ = 0.171 ± 0.102 (stat.) ± 0.058 (syst.), which is consistent at the 27% C.L. with the standard model.
Book Synopsis Measurement of the W Boson Helicity in Top Quark Decays by :
Download or read book Measurement of the W Boson Helicity in Top Quark Decays written by and published by . This book was released on 2007 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the fraction, f+, of right-handed W bosons produced in top quark decays is presented. This analysis is based on a sample corresponding to an integrated luminosity of 370 pb−1, collected by the D0 detector at the Fermilab Tevatron p{bar p} Collider at √s = 1.96 TeV. The helicity angle, [theta]*, is reconstructed for each lepton. f+ is determined by comparing the cos [theta]* distribution from the data with that for the expected background and signal for various values of f+. The fraction of longitudinal W bosons, f°, is assumed to be 0.7 as predicted by the standard model. This yields f+ = 0.109 ± 0.094 (stat) ± 0.063 (syst), consistent with the standard model prediction of f+ = 3.6x 10−4. The possibility that both f+ and f° stray from standard model values is also investigated. In this case cos [theta]* distributions for each possible W helicity state, along with the backgrounds, are fit to the cos [theta]* distribution for the data. The best fit values are f+ = 0.82 ± 0.30(stat) and f° = -0.58 ± 0.50(stat).
Book Synopsis Measurement of the W-boson Helicity Fractions in Top-quark Decays at CDF. by :
Download or read book Measurement of the W-boson Helicity Fractions in Top-quark Decays at CDF. written by and published by . This book was released on 2007 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the fractions F0 and F+ of longitudinally polarized and right-handed W bosons in top-quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 955 pb−1. We select t{bar t} candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses 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 momentum in the top-quark rest-frame. The cos[theta]* distribution in the data is determined by full kinematic reconstruction of the t{bar t} candidates. We find F0= 0.59 ± 0.12(stat){sup +0.07}{sub -0.06}(syst) and F+=-0.03 ± 0.06(stat){sup +0.04}{sub -0.03}(syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W bosons of F+ ≤ 0.10 at the 95% confidence level.
Book Synopsis Measurement of the W Boson Helicity in Top Quark Decays Using 5.4 Fb$^{\boldsymbol{-1}}$ of $\boldsymbol{p\bar{p}}$ Collision Data by :
Download or read book 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 published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.)].
Book Synopsis 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) by :
Download or read book 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 published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis A Measurement of the Helicity of W Bosons Produced in Top-quark Decays by : Nathan J. Goldschmidt
Download or read book A Measurement of the Helicity of W Bosons Produced in Top-quark Decays written by Nathan J. Goldschmidt and published by . This book was released on 2005 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurement of W Boson Helicity Fractions in T Anti-t Decays at DZero and CDF. by :
Download or read book Measurement of W Boson Helicity Fractions in T Anti-t Decays at DZero and CDF. written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The properties of the W boson can be probed in top quark decays t --> bW. The CDF and DZero collaborations have released updated measurements of the W boson helicity fractions f0, f+ and f. The analysis techniques and updated measurements are discussed. This paper summarizes the talk given at the DIS2008 conference.
Book Synopsis 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} by :
Download or read book 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 published by . This book was released on 2013 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Study of Future Measurements of W Boson Helicity in T -] Wb at CDF. by :
Download or read book A Study of Future Measurements of W Boson Helicity in T -] Wb at CDF. written by and published by . This book was released on 2002 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: The interactions of the top quark will soon be coming under greater scrutiny at CDF with Run II of the Fermilab Tevatron collider. This investigation gauges CDF's improved ability to measure the helicity of W bosons produced in top quark decays. Such measurements will provide a direct indication of the spin structure of the weak interaction responsible for the top decay process. Simulated CDF Run II data is used to study the W helicity sensitivity of the muon momentum in [mu] + jets events, as limited by both statistical and systematic uncertainties. Optimization of helicity measurements via appropriate choices of event variables and data criteria is also addressed.
Book Synopsis Determination of W Boson Helicity Fractions in Top Quark Decays in Pp Collisions at CDF RunII and Production of Endcap Modules for the ATLAS Silicon Tracker by : Shulamit Moed
Download or read book Determination of W Boson Helicity Fractions in Top Quark Decays in Pp Collisions at CDF RunII and Production of Endcap Modules for the ATLAS Silicon Tracker written by Shulamit Moed and published by . This book was released on 2007 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: La deuxième partie concerne la mesure des fractions d'hélicité longitudinale et droite du boson W dans la désintégration du quark top avec le détecteur CDF au Fermilab. Le résultat de cette mesure constitue un test très sensible du Modèle Standard des interactions électro-faibles. Pour la première fois les deux fractions d'hélicité ont été déterminées non seulement séparément mais aussi simultanément.
Book Synopsis Measurement of the Helicity Fractions of W Bosons from Top Quark Decays Using Fully Reconstructed T Anti-t Events with CDF II. by :
Download or read book Measurement of the Helicity Fractions of W Bosons from Top Quark Decays Using Fully Reconstructed T Anti-t Events with CDF II. written by and published by . This book was released on 2006 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present a measurement of the fractions F0 and F+ of longitudinally polarized and right-handed W bosons in top quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 318 pb−1. They select t{bar t} candidate events with one lepton, at least four jets, and missing transverse energy. The helicity measurement uses 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 momentum in the top quark rest frame. The cos [theta]* distribution in the data is determined by full kinematic reconstruction of the t{bar t} candidates. They find F0 = 0.85{sub -0.22}{sup +0.15}(stat)±0.06(syst) and F+ = 0.05{sub -0.05}{sup +0.11}(stat) ± 0.03(syst), which is consistent with the standard model prediction. They set an upper limit on the fraction of right-handed W bosons of F+
Book Synopsis Combination of CDF and D0 Results on the W Boson Mass and Width by :
Download or read book Combination of CDF and D0 Results on the W Boson Mass and Width written by and published by . This book was released on 2008 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results on the direct measurements of the W-boson mass and width, based on the data collected by the Tevatron experiments CDF and D− at Fermilab are summarized and combined. The CDF Run-0 (1988-1889) and Run-I (1992-1995) results have been re-averaged using the BLUE method and combined with Run-I D− results and the latest published results from CDF taken from the first period of Run-II (2001-2004). The results are corrected to have consistency between the parton distribution functions and electroweak parameters. The resulting Tevatron averages for the mass and total decay width of the W boson are: M{sub W} = 80432 ± 39 MeV and [Lambda]{sub W} = 2056 ± 62 MeV. The inclusion of a preliminary Run-II measurement of [Lambda]{sub W} from D−0 gives [Lambda]{sub W} = 2050 ± 58 MeV.
Book Synopsis Measurement of the Helicity of W Bosons in Top Quark Decays by : David J. Winn
Download or read book Measurement of the Helicity of W Bosons in Top Quark Decays written by David J. Winn and published by . This book was released on 2000 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurement of the Helicity of W Bosons in Top-quark Decays by :
Download or read book Measurement of the Helicity of W Bosons in Top-quark Decays written by and published by . This book was released on 2005 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We measure the branching fraction of the top quark to longitudinally and right-handed polarized W bosons, F0 and F+, using approximately 200 pb−1 of p{bar p} collisions collected by the CDF II detector. We analyze two quantities sensitive to the W helicity: the invariant mass of the charged lepton and the bottom-quark jet in the decay t 2!Wb 2!l[nu]b (where l = e or [mu]), and the transverse momentum of the charged lepton. We find F0 = 0.74{sub -0.34}{sup +0.22}, and F+
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