Measurement of the W-boson Polarisation in Top-quark Decays with the ATLAS Detector PDF Download

Author: Andrea Helen Knue
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Languages : en
Pages : 0

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A measurement of the W-boson polarisation in top-quark decays is presented. The top-antitop events were produced in proton-proton collisions at a centre-of-mass energy of sqrt{s} = 7 TeV at the LHC. The data set corresponds to an integrated luminosity of 4.7 fb-1 and was collected by the ATLAS experiment. The measurement was performed in the lepton+jets channel which is characterised by an isolated electron or muon, missing transverse energy and at least four jets. One of the jets has to be identified as a b-jet. The W-boson polarisation was studied using the angular distribution of the cha ...

Author: Gvantsa Mchedlidze
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Languages : en
Pages : 0

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A measurement of the $W$ boson polarisation in top quark decays is presented. The top anti-top pairs were produced at a centre of mass energy of $\sqrt{s}=8$ \tev \ using proton-proton collisions at the LHC. The data sample corresponds to an integrated luminosity of$\int{\mathcal{L}dt}=20.2$ fb$^{-1}$ recorded by the ATLAS detector in 2012. The measurement was performed in the dilepton channel, which is characterised by two leptons (electron or muon) with opposite electric charge, missing transverse energy from two neutrinos, and at least two jets. One of these jets is required to be tagged ...

Author: Gvantsa Mchedlidze
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Languages : en
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Book Description
A measurement of the $W$ boson polarisation in top quark decays is presented. The top anti-top pairs were produced at a centre of mass energy of $\sqrt{s}=8$ \tev \ using proton-proton collisions at the LHC. The data sample corresponds to an integrated luminosity of$\int{\mathcal{L}dt}=20.2$ fb$^{-1}$ recorded by the ATLAS detector in 2012. The measurement was performed in the dilepton channel, which is characterised by two leptons (electron or muon) with opposite electric charge, missing transverse energy from two neutrinos, and at least two jets. One of these jets is required to be tagged...

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Languages : en
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We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb−1 of p{bar p} collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c2, three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f0) and right-handed (f+) W bosons yields the model-independent results f0 = 0.88 ± 0.11(stat) ± 0.06(syst) and f+ = -0.15 ± 0.07(stat) ± 0.06(syst) with a correlation coefficient of -0.59. A measurement of f0 (f+) constraining f+ (f0) to its standard model value of 0.0 (0.7) yields f0 = 0.70 ± 0.07(stat) ± 0.04(syst) (f+ = 0.01 ± 0.02(stat) ± 0.05(syst)). All these results are consistent with standard model expectations.

Author: Mohammad Jawad Kareem
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Languages : en
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Precise measurements of the properties of the top quark allow for testing the Standard Model (SM) and can be used to constrain new physics models. The top quark is predicted in the SM to decay almost exclusively to a W boson and b-quark. Thus, studying the Wtb vertex structure at high precision and in detail is motivated. This thesis presents a measurement of the W boson helicity fractions in top quark decays with top/anit-top events in the lepton + jets final state using proton-proton collisions at a centre-of-mass energy of 8 TeV recorded in 2012 with the ATLAS detector at the LHC. The da...

Author: Georges Aad
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Languages : en
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Author: Trevor Neil Vickey
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Languages : en
Pages : 348

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Author: Sebastián Pedraza López
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Languages : en
Pages : 0

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Languages : en
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A measurement of the polarization of the W boson from top quark decay is an excellent test of the V-A form of the charged-current weak interaction in the standard model. Since the longitudinal W boson is intimately related to the electroweak symmetry breaking mechanism, and the standard model gives a specific prediction for the fraction of longitudinal W bosons from top decays, it is of particular interest for study. This thesis presents a measurement of W boson polarization in top quark decay through an analysis of the cos [theta]* distribution in the lepton-plus-jets channel of t[bar t] candidate events from p[bar p] collisions at [radical]s = 1.96 TeV. This measurement uses an integrated luminosity of [approx]162 pb[sup -1] of data collected with the CDF Run II detector, resulting in 31 t[bar t] candidate events with at least one identified b jet. Using a binned likelihood fit to the cos [theta]* distribution from the t[bar t] candidate events found in this sample, the fraction of W bosons with longitudinal polarization is determined to be F[sub 0] = 0.99[sub -0.35][sup +0.29](stat.) [+-] 0.19(syst.), F[sub 0]> 0.33 [at] 95% CL. This result is consistent with the standard model prediction, given a top quark mass of 174.3 GeV/c[sup 2], of F[sub 0] = 0.701 [+-] 0.012.

Author:
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Languages : en
Pages : 8

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