January 20, 2021 Doctoral Dissertation Open Access

Seith, David

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      "affiliation": "KIT/ETP", 
      "name": "Seith, David"
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  "datePublished": "2021-01-20", 
  "description": "<p>A measurement of the inclusive and differential $t$-channel single top quark production cross section is performed in this thesis.<br>\nThe measurement uses 137 fb$^{-1}$ of data recorded at the CMS experiment at the LHC with a center-of-mass energy of 13 TeV.<br>\nEvents are selected with exactly one muon or electron and two or three jets, of which at least one is identified as originating from a bottom quark.<br>\nIn the analysis an improved technique for reconstructing the top quark has been developed that makes use of a neural network in order to achieve a better description of the top quark&#39;s kinematic variables.<br>\nA multiclassification BDT is used to classify events into different process categories.</p>\n\n<p>The cross sections are extracted from a fit to the output distribution of the multiclassification BDT.<br>\nThe inclusive cross section of $t$-channel single top quark production was measured to be $\\sigma_{t} = 130 \\pm 20 \\, \\mathrm{pb}$ and the cross section of top antiquark production to be $\\sigma_{\\bar{t}} = 80 \\pm 15 \\, \\mathrm{pb}$.</p>\n\n<p>The differential cross section measurement is performed via unfolding.<br>\nThe measured differential cross sections as a function of the top quark transverse momentum and rapidity agree with the predictions of the SM.<br>\nThree angular variables, $\\cos x, \\cos y$, and $\\cos z$, are defined in the top quark rest frame between the charged lepton from the top quark decay and three axes, which are defined based on the direction of the spectator quark and the beamline axis.<br>\nThe asymmetries in these distributions are measured to be:<br>\n&nbsp;&nbsp;&nbsp; $A_{x}(t+\\bar{t})=-0.07\\pm0.09$,<br>\n&nbsp;&nbsp;&nbsp; $A_{y}(t+\\bar{t})=0.00\\pm0.05$, and<br>\n&nbsp;&nbsp;&nbsp; $A_{z}(t+\\bar{t})=0.42\\pm0.08$.<br>\nThe measured asymmetries are used to constraint the magnitude of possible right handed couplings between the top quark and the W boson.</p>", 
  "headline": "Measurement of the inclusive and differential $t$-channel single top quark production cross section at 13 TeV with the CMS experiment", 
  "image": "https://publish.etp.kit.edu/static/img/logos/zenodo-gradient-round.svg", 
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  "keywords": [
    "single top", 
    "t channel", 
    "LHC", 
    "CMS", 
    "13 TeV", 
    "Run 2", 
    "top quark", 
    "cross section", 
    "polarization"
  ], 
  "name": "Measurement of the inclusive and differential $t$-channel single top quark production cross section at 13 TeV with the CMS experiment", 
  "url": "https://publish.etp.kit.edu/record/22026"
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