January 12, 2021 Master Thesis Open Access

Pfeffer, Emanuel

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{
  "abstract": "<p>In this thesis, the interplay of two elementary particles of the SM, the two heaviest quarks top (t) and bottom (b), is studied in detail. Processes in which a top quark-antiquark pair occurs in associated production with two bottom quarks (tt+bb)&nbsp;play an important role in particle physics. The two quarks show a high mass difference and their associated production is therefore particularly difficult to model, accompanied by large uncertainties [6]. In addition, events involving this process constitute a large irreducible background in measurements of tt+H production in H&nbsp;&rarr;&nbsp;bb&nbsp;decays. These measurements are an essential test of the SM and an important constraint of physics beyond the SM. Consequently, the tt+bb&nbsp;process needs to be thoroughly understood.</p>\n\n<p>Events comprising tt+bb&nbsp;processes are analyzed at two different Monte Carlo event simulation levels in this thesis.<br>\nThe first part compares different existing event simulations used at the CMS experiment for the tt+bb&nbsp;process in the single-lepton channel and investigates possible differences in the modeling. The analysis is technically realized in a way that allows a direct comparison of the simulations with those of the ATLAS experiment. The comparison of simulations of both experiments is performed building on this analysis. This enables the design of a common strategy between ATLAS and CMS.</p>\n\n<p>The second part focuses on strategies for assigning b jets to their origin. Since top quarks decay into b quarks almost exclusively, the final state of an event involving the tt+bb&nbsp;process usually consists of four or more b jets. However, it is unknown in the event reconstruction which b jets result from top quark decays and which originate from additional gluon radiation and subsequent splittings into pairs of b quarks in the event.</p>", 
  "author": [
    {
      "family": "Pfeffer, Emanuel"
    }
  ], 
  "id": "22082", 
  "issued": {
    "date-parts": [
      [
        2021, 
        1, 
        12
      ]
    ]
  }, 
  "language": "eng", 
  "title": "Studies on tt+bb production at the CMS experiment", 
  "type": "thesis"
}