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@PHDTHESIS{Nowatschin:330925,
      author       = {Nowatschin, Dominik},
      othercontributors = {Haller, Johannes and Meyer, Andreas},
      title        = {{S}earch for vector-like quarks using jet substructure
                      techniques with the {CMS} experiment},
      school       = {Universität Hamburg},
      type         = {Dr.},
      address      = {Hamburg},
      publisher    = {Verlag Deutsches Elektronen-Synchrotron},
      reportid     = {PUBDB-2017-07360, DESY-THESIS-2017-026},
      series       = {DESY-THESIS},
      pages        = {215},
      year         = {2017},
      note         = {Universität Hamburg, Diss., 2017},
      abstract     = {In this thesis, a search for pair produced vector-like $T$
                      quarks in $pp$ collision data from the LHC at $\sqrt{s} =
                      13\,\text{Te}\kern-0.06667em\text{V}$ is presented. The data
                      were collected with the CMS detector and correspond to an
                      integrated luminosity of up to $2.6\,\mathrm{fb}^{-1}$.
                      Vector-like quarks are hypothetical new particles predicted
                      by many extensions of the Standard Model in which the Higgs
                      boson is a composite state of an unknown strong
                      interaction.Vector-like $T$ quarks are assumed to decay via
                      three different decay modes to either $bW$, $tZ$ or $tH$,
                      with branching fractions that are not fixed and can vary
                      depending on the particular model featuring vector-like
                      quarks.This search focuses on decays of the $T{\overline T}$
                      system in which at least one muon or electron is present in
                      the final state, and in which at least one of the $T$ quarks
                      decays to a top quark and a Higgs boson.As the $T$ quarks
                      are expected to be quite heavy, their decay products are
                      significantly Lorentz-boosted in the reference frame of the
                      $T{\overline T}$ system. The subsequent decay products of
                      the Higgs boson are then emitted with a very small angle
                      between them. This search is optimised for the main decay
                      channel of the Higgs boson to two bottom quarks and attempts
                      to reconstruct the two $b$ quarks within a single jet with a
                      large cone size. Dedicated jet substructure techniques, in
                      combination with algorithms to identify jets originating
                      from the fragmentation of a $b$ quark, are then used to
                      reconstruct the entire $H \rightarrow b{\overline b}$
                      decay.The event categories of this search are also combined
                      with the categories of a search for pair-produced $T$ quarks
                      that focuses on the $T \rightarrow bW$ decay. This approach
                      provides a high sensitivity to $T{\overline T}$ production
                      for many different combinations of branching fractions to
                      the three possible decay modes.No excess of the data above
                      the expected background contribution from the Standard Model
                      is observed in any of the final event categories. Upper
                      limits on the $T{\overline T}$ production cross section are
                      calculated at 95\% confidence level and lower mass limits
                      for vector-like $T$ quarks are set for various assumptions
                      of their decays: for branching fractions corresponding to an
                      electroweak isospin singlet $T$ quark, masses below
                      860$\,\text{Ge}\kern-0.06667em\text{V}$ are excluded, while
                      for an electroweak isospin doublet, $T$ quarks are excluded
                      with masses up to 830$\,\text{Ge}\kern-0.06667em\text{V}$.
                      For other branching fraction combinations, lower mass limits
                      are derived ranging from
                      710$\,\text{Ge}\kern-0.06667em\text{V}$ to
                      940$\,\text{Ge}\kern-0.06667em\text{V}$.These exclusion
                      limits are comparable to and for some branching fraction
                      assumptions even higher than exclusion limits set by the CMS
                      experiment using a data set corresponding to
                      $19.7\,\mathrm{fb}^{-1}$ at $\sqrt{s} =
                      8\,\text{Te}\kern-0.06667em\text{V}$.},
      cin          = {UNI/EXP / CMS},
      cid          = {$I:(DE-H253)UNI_EXP-20120731$ / I:(DE-H253)CMS-20120731},
      pnm          = {611 - Fundamental Particles and Forces (POF3-611)},
      pid          = {G:(DE-HGF)POF3-611},
      experiment   = {EXP:(DE-H253)LHC-Exp-CMS-20150101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)29 / PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2017-07360},
      url          = {https://bib-pubdb1.desy.de/record/330925},
}