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@PHDTHESIS{Kitali:435392,
      author       = {Kitali, Vincent},
      title        = {{S}earch for invisible decays of the {H}iggs boson produced
                      invector-boson fusion in final states with jets and large
                      missingtransverse energy with the {ATLAS} detector},
      school       = {University of Hamburg},
      type         = {Dissertation},
      reportid     = {PUBDB-2020-00626},
      pages        = {214},
      year         = {2020},
      note         = {Dissertation, University of Hamburg, 2020},
      abstract     = {The Standard Model of particle physics is a very successful
                      theory, but it leaves some openquestions. Especially the
                      topic of dark matter is a very active field of research and
                      the discoveryof dark matter candidates might be accessible
                      to modern collider experiments. Answering openquestions of
                      the Standard Model is one of the greater goals of this
                      work.The dark matter candidates might interact with the
                      recently discovered Higgs boson andwould appear invisible to
                      a particle detector. This motivates a search for invisible
                      decays ofthe Higgs boson produced in vector-boson fusion.
                      The search is looking for a pair of wellseparated, highly
                      energetic jets and missing transverse energy in the final
                      state. The analysisuses 36.1 fb−1of proton–proton
                      collision data recorded at a centre-of-mass energy of 13 TeV
                      in2015 and 2016 with the ATLAS experiment at the LHC. The
                      main backgrounds are leptonicallydecaying vector bosons.
                      These backgrounds are constrained in dedicated data control
                      regions.The multijet background is small, since it can only
                      result from mismeasurements of thejet transverse momentum,
                      but it is challenging to quantify. The jet response is a
                      measure forthe mismeasurement of jet transverse momenta. To
                      study how well it is simulated in areasof extreme
                      mismeasurements the non-Gaussian tails of these
                      distributions are quantified in acomparison between data and
                      simulation. This is achieved by modelling the Gaussian
                      corewith fits. In order to see the effect in data the
                      momentum balance of jet pairs is considered byusing an
                      extrapolation to pure dijet events. The effort is undertaken
                      with a new jet definition,particle flow jets, as well as
                      topocluster jets. For both of them simulation and data are
                      in goodagreement. This leads to systematic uncertainties
                      small enough to have a negligible impact onthe analysis.The
                      systematic uncertainty resulting from the jet energy
                      resolution is one of the main limitations to the sensitivity
                      of the search. This is addressed with the global sequential
                      calibration(GSC), a simulation-driven method that removes
                      the dependencies of jet momenta on a selection of detector
                      variables in order to improve the jet resolution. The
                      calibration leads to ajet resolution improvement of up to
                      $20\%.$ The GSC is fully derived for particle flow jets
                      forthe first time, allowing performance comparisons between
                      different kinds of jet reconstructionalgorithms.The search
                      is able to derive a new observed (expected) limit on the
                      Higgs to invisible branching fraction of 0.37 (0.28) at
                      $95\%$ confidence level. The results are also interpreted
                      consideringa Higgs portal model, treating the invisible
                      decay products as dark matter candidates. The resulting
                      limits on the cross-section for the DM candidate to interact
                      with an atomic nucleus isbetween 10−46 cm2and 10−42
                      cm2at $90\%$ confidence level depending on the DM mass
                      andspin.},
      keywords     = {thesis (INSPIRE) / p p: scattering (INSPIRE) / p p:
                      colliding beams (INSPIRE) / jet: transverse momentum
                      (INSPIRE) / jet: resolution (INSPIRE) / Higgs particle:
                      invisible decay (INSPIRE) / jet: energy resolution (INSPIRE)
                      / jet: momentum (INSPIRE) / jet: multiple production
                      (INSPIRE) / track data analysis: jet (INSPIRE) / dark
                      matter: mass (INSPIRE) / vector boson: fusion (INSPIRE) /
                      transverse energy: missing-energy (INSPIRE) / background
                      (INSPIRE) / particle flow (INSPIRE) / calibration (INSPIRE)
                      / ATLAS (INSPIRE) / Higgs particle: branching ratio: upper
                      limit (INSPIRE) / non-Gaussianity (INSPIRE) / CERN LHC Coll
                      (INSPIRE) / sensitivity (INSPIRE) / performance (INSPIRE) /
                      dark matter: interaction (INSPIRE) / WIMP nucleus:
                      scattering (INSPIRE) / channel cross section: upper limit
                      (INSPIRE) / experimental results (INSPIRE) / 13000 GeV-cms
                      (INSPIRE)},
      cin          = {ATLAS},
      cid          = {I:(DE-H253)ATLAS-20120731},
      pnm          = {611 - Fundamental Particles and Forces (POF3-611) / PHGS,
                      VH-GS-500 - PIER Helmholtz Graduate School
                      $(2015_IFV-VH-GS-500)$},
      pid          = {G:(DE-HGF)POF3-611 / $G:(DE-HGF)2015_IFV-VH-GS-500$},
      experiment   = {EXP:(DE-H253)LHC(machine)-20150101},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:gbv:18-101485},
      doi          = {10.3204/PUBDB-2020-00626},
      url          = {https://bib-pubdb1.desy.de/record/435392},
}